Over-the-Counter Antihistamines: Brands and Side Effects

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Common anti-allergy drugs, known as antihistamines, include Benadryl, Zyrtec, Claritin, and others. They work by reducing the impact of histamine in your body, which relieves your allergy symptoms.

When you have an allergic reaction, your body releases a substance called histamine. Histamine causes allergy symptoms when it binds to receptors on certain cells in your body. Antihistamines work by decreasing the effects of histamine on certain cell receptors.

Over-the-counter (OTC) antihistamines can help treat symptoms such as:

• congestion
• runny nose
• sneezing
• itching
• nasal swelling
• hives
• skin rashes
• itchy and watery eyes

Read on to learn how the different brand-name antihistamines can help treat your allergy symptoms.

First-generation OTC oral antihistamines, including diphenhydramine and chlorpheniramine, are the oldest group. They are sedating, which means they’re likely to make you drowsy after you use them. They also don’t last as long in your system, so they require more frequent dosing than the newer generations. First-generation brands include Benadryl and Chlor-Trimeton.

Benadryl

The first-generation antihistamine diphenhydramine is the main active ingredient in Benadryl. Benadryl helps relieve runny nose, sneezing, itchy or watery eyes, and nose or throat itching. These symptoms may be due to hay fever, other upper respiratory allergies, or the common cold. Benadryl can also be used to treat hives and to reduce redness and itching.

It comes in a tablet, a chewable tablet, a tablet that dissolves in your mouth, a capsule, a liquid-filled capsule, and a liquid. Benadryl also comes in topical forms, such as creams, gels, and sprays, to treat allergic skin conditions such as hives.

Other common OTC brands that include the antihistamine diphenhydramine include:

• Banophen
• Siladryl
• Unisom
• Benadryl-D Allergy Plus Sinus
• Robitussin Severe Multi-Symptom Cough Cold + Flu Nighttime
• Sudafed PE Day/Night Sinus Congestion

Chlor-Trimeton

Chlorpheniramine is the main active ingredient in Chlor-Trimeton. It helps relieve runny nose, sneezing, itchy or watery eyes, and nose and throat itching from hay fever. It also helps relieve other respiratory allergies.

It comes in an immediate-release tablet, an extended-release tablet, a chewable tablet, a lozenge, a capsule, and a liquid.

Other common brands with chlorpheniramine as a main active ingredient include:

• Aller-Chlor
• Chlorphen-12
• Alka-Seltzer Plus Cold & Cough Liquid Gels
• Allerest Maximum Strength
• Comtrex

Side effects of first-generation antihistamines

Some of the more common side effects of first-generation antihistamines can include:

• drowsiness
• dry mouth, nose, and throat
• headache

Some side effects that are not as common include:

• dizziness
• nausea
• vomiting
• loss of appetite
• constipation
• chest congestion
• muscle weakness
• hyperactivity, especially in children
• nervousness

Some serious side effects can include:

• vision problems
• trouble urinating or pain with urinating

All of these side effects are more common in older people.

Warnings

If you have an enlarged prostate that makes it difficult for you to urinate, you should talk to your doctor before using first-generation antihistamines. These drugs can make your urination problem worse. You should also talk to your doctor before using these drugs if you have any of these health concerns:

• trouble breathing from emphysema or chronic bronchitis
• glaucoma
• high blood pressure
• heart disease
• seizures
• thyroid problems

If you take other drugs that can make you drowsy, such as sedatives or tranquilizers, talk to your doctor before using first-generation antihistamines. You should also avoid drinking alcohol with any antihistamine because it can increase the side effect of drowsiness.

The newer second-generation and third-generation OTC oral antihistamines were developed to target their action on more specific receptors. This helps decrease side effects, including drowsiness. Also, these drugs work longer in your body so you need fewer doses.

Zyrtec

Cetirizine is the main active ingredient in Zyrtec. It helps relieve runny nose, sneezing, itchy and watery eyes, and nose or throat itching from hay fever and other upper respiratory allergies. Zyrtec can also be used to help relieve redness and itching due to hives. Zyrtec comes in a tablet, a chewable tablet, a tablet that dissolves in your mouth, a liquid-filled capsule, and a syrup.

Other common OTC brands with cetirizine as the main active ingredient include:

• Aller-Tec
• Alleroff
• Zyrtec-D
• Wal Zyr-D
• Cetiri-D

Side effects

Some common side effects of Zyrtec can include:

• drowsiness
• headache
• stomach pain

Serious side effects can include trouble breathing or swallowing.

Warnings

• Talk to your doctor if you use the bronchodilator theophylline. Zyrtec can interact with this drug and increase your risk of side effects.
• Avoid taking Zyrtec with alcohol. Although cetirizine causes less drowsiness than a first-generation antihistamine, it can still make you drowsy. Drinking alcohol while you take it can increase this drowsiness.
• Talk to your doctor before using Zyrtec if you have liver or kidney disease. Liver and kidney disease can both affect how your body processes and removes cetirizine.
• You should also talk to your doctor before using Zyrtec if you have asthma. In rare cases, cetirizine has been shown to cause bronchospasms.

Claritin

Loratadine is the main active ingredient in Claritin. It helps relieve runny nose, sneezing, itchy, watery eyes, and itching of the nose or throat due to hay fever and other upper respiratory allergies. Claritin can also be used to treat hives. It comes in a tablet, a tablet that dissolves in your mouth, a chewable tablet, a liquid-filled capsule, and a syrup.

Loratadine is also the main active ingredient in these other OTC brands:

• Claritin-D
• Alavert
• Alavert-D
• Wal-itin

Side effects

Some of the common side effects of Claritin can include:

• headache
• drowsiness

Serious side effects of Claritin can include allergic reactions. Symptoms can include:

• rash
• itching
• trouble breathing or swallowing
• swelling of your face, throat, tongue, lips, eyes
• hoarseness

Warnings

• Talk to your doctor before using Claritin if you have liver or kidney disease. Liver and kidney disease can both affect how your body processes and removes loratadine. This can cause more of the drug to stay in your body and increase your risk of side effects.
• You should also talk to your doctor before using Claritin if you have asthma. In rare cases, loratadine has been shown to cause bronchospasms.

Allegra

Fexofenadine is the main active ingredient in Allegra. It helps relieve runny nose, sneezing, itchy and watery eyes, and itching of the nose or throat due to hay fever or other upper respiratory allergies. Allegra can also be used to treat hives and skin rash. It comes in a tablet, a tablet that dissolves in your mouth, a gel-coated capsule, and a liquid.

Side effects

Some of the common side effects of Allegra can include:

• headache
• dizziness
• diarrhea
• vomiting
• pain in your arms, legs, or back
• pain during menstrual periods
• cough
• upset stomach

Serious side effects of Allegra can include allergic reaction. Symptoms include:

• hives
• rash
• itching
• trouble breathing or swallowing
• swelling of your face, throat, tongue, lips, eyes

Warnings

• Talk to your doctor before you use Allegra if you take the antifungal ketoconazole, the antibiotics erythromycin or rifampin, or any antacids. These drugs can all interact with Allegra to either increase your risk of side effects or decrease the effectiveness of Allegra.
• Avoid drinking fruit juice while taking Allegra. Fruit juice can also decrease the amount of Allegra that your body absorbs. This can make the drug less effective.
• If you have kidney disease, talk to your doctor before using Allegra. Kidney disease interferes with your body’s removal of Allegra. This can lead to an increased risk of side effects.

If you have allergies, you have a range of choices for OTC medications. These include brand-name antihistamines such as:

• Benadryl
• Chlor-Trimeton
• Zyrtec
• Claritin
• Allegra

If you’re not sure which medication might be best for you, talk to your doctor or pharmacist. And if you take other medications to treat allergy symptoms, make sure that the active ingredients are not the same or in the same drug class as the active ingredient in the antihistamine you want to take. You don’t want to take too much of any particular drug. To help prevent this, always check with your doctor or pharmacist.

If you’d like to shop for antihistamines, you’ll find a range of products here.

If you need help finding an Allergist and Immunologist, then check out our FindCare tool here.

Why Benadryl is no longer recommended as 1st choice for allergy medication

More than two years after allergy experts recommended newer antihistamines and recommended against using Benadryl as a first-line treatment, many Canadians are still reaching for that recognizable brand name over others.

In October 2019, the Canadian Society of Allergy and Clinical Immunology (CSASI) put out a position statement regarding oral allergy medication, stating that newer antihistamines were safer than first-generation ones, and that they should be recommended over older staples like Benadryl due to a higher rate of potential side effects. The position statement referred specifically to medications that treat non-life-threatening allergic reactions such as hay fever and hives.

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If it’s news to you that Benadryl is no longer recommended as a first-line treatment for common allergies, you’re not the only one. In 2022, it’s not only adult patients and parents who are still influenced by brand familiarity and haven’t made the switch — some doctors are as well, experts say.

“I think there are a fair number of pediatricians who still recommend Benadryl for allergies,” Daniel Flanders, owner and executive director of Kindercare Pediatrics in Toronto, Ontario, told CTVNews. ca in a phone interview.

“And if you speak to an allergist, they would simply say that that’s outdated advice.”

Benadryl is one of the most well-known brands for allergy medication, with numerous products available to buy without a prescription, including versions specifically made for children. Benadryl is approved by Health Canada, which has deemed it safe for over-the-counter use, concluding in a recent safety review of first-generation antihistamines that there hasn’t been any change in risk that would prompt it to change the drug to prescription-only.

While both first and second-generation antihistamines bind to receptors in the brain and spinal cord to block the release of histamines — the chemicals that cause allergy symptoms — first-generation crosses the blood-brain barrier and causes more sedation in patients, something that was corrected in second-generation antihistamines.

Because of this difference, first-generation antihistamines like Benadryl are associated with more side effects such as increased drowsiness, issues with motor functions and working memory, as well as a risk of hallucination or even death in the event of an overdose.

But if many experts have believed for years that Benadryl shouldn’t be the first choice for oral allergy medication anymore, why are many Canadians and doctors unaware of this?

“Unfortunately far too often, physicians and other health-care practitioners, including pharmacists and paramedics, continue to commonly recommend Benadryl as a first line antihistamine for treatment of allergic symptoms, including symptoms from food allergy,” CSACI told CTVNews.ca in an email, adding that its 2019 messaging has “still not reached many health-care practitioners.”

Flanders said that while he’s not aware of any doctors in his clinic still recommending Benadryl, there are likely many across Canada still turning to the well-known allergy medication to treat mild allergies.

“I would say probably for 10 years it has been the case that we’ve known that it’s better to use the second and third generation antihistamines preferentially over Benadryl, but […] one of the funny things about medicine is that it does take a long time for information to trickle down from research through to practice,” he said.

“It is measured in years. It’s not uncommon, but it takes a good 10 years for the standard of care for the practice to adjust to some of the changes that science discovers.”

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Flanders said if he had to make an estimate, anywhere from 25 to 50 per cent of pediatricians may still be recommending Benadryl as a first line treatment, though he cautioned that this is just his personal assessment.

“I’m hopeful that more than half of my colleagues are making that correct recommendation [instead of Benadryl],” he said.

A big reason that Benadryl is still recommended by health-care professionals is the familiarity of that brand name, which has been a giant in allergy medication for decades.

“Benadryl has so much recognition as an allergy remedy,” Flanders said. “The trade name is so well known, and so commonly used that I could imagine it would take a whole lot of work to sort of deprogram and reprogram parents’ minds. And also the minds of doctors who are not sort of keeping up with the cutting edge [of medicine].”

It was a sentiment that CSACI echoed.

“The familiarity of health-care practitioners, parents and adult patients with Benadryl and other first generation antihistamines makes it difficult to motivate changes in practice,” the organization said.

WHY DID CSACI DECIDE BENADRYL SHOULDN’T BE RECOMMENDED?

More than two years ago, CSACI put out a paper explaining that newer antihistamines are just as effective and safer than first-generation antihistamines such as Benadryl, and that they should always be recommended over older antihistamines.

CSACI says bilastine and cetirizine are among the newer antihistamines recommended.

The active ingredient in Benadryl sold in Canada is diphenhydramine, and it’s one of the oldest first-generation antihistamines, having been available for sale since 1946.

In the position statement, CSASI explained that older antihistamines are associated with more severe side effects than second and third generation antihistamines which became available in Canada starting in the 1980s and had to pass high-quality trials.

“It is always preferred to use safer and more effective medications,” CSACI told CTVNews.ca in an email. “First generation antihistamines are significantly more likely to cause side effects, including sedation, poor sleep quality, and poor cognitive performance (including poor school and work performance). In addition, overdoses of first generation antihistamines can cause severe toxicity.”

Johnson & Johnson, the company that sells Benadryl in Canada, did not respond to a request for comment from CTVNews.ca.

In 2019, the company told the Canadian Press that “Benadryl products have been trusted by doctors and moms for more than 60 years to provide effective symptom relief from allergies and allergic reactions,” and that the products are approved by Health Canada and “when used as directed, are safe and effective.”

CSACI’s position statement explained that newer antihistamines have less serious side effects associated with them, and that as of 2019, accidental exposure to higher levels of second and third generation antihistamines had not resulted in severe adverse events, unlike first generation antihistamines.

In 2020, a TikTok “challenge” spurred some teenagers to take enough Benadryl to induce hallucinations, which resulted in several teens being rushed to hospital.

The CSACI statement mentioned that in Canada, online surveys had shown that Benadryl was, at the time, the “most recommended antihistamine for allergic symptoms in children in each of the last 7 years.”

WHY IS BENADRYL STILL AVAILABLE OVER THE COUNTER?

It’s important to note that Benadryl isn’t considered dangerous — when instructions are followed, serious side effects are rare.

CSACI’s position was that there are new options that are just as effective and have fewer side effects overall, or milder side effects.

“I wouldn’t so much say that one should never use [Benadryl], it just doesn’t make sense to use it currently or in present day, because there are alternatives that are just as good and have a better side effect profile,” Flanders explained.

“Why would you take a medication that you know has significant side effects when you can take another medication that does the exact same thing, but without the side effects?”

After CSACI released this position statement in 2019, there was a flurry of articles that questioned whether Benadryl should be available as over-the-counter medication. As a result, Health Canada announced that while products containing diphenhydramine met the requirements of the Food and Drugs Act, they would be assessing “to determine if further risk mitigation measures for diphenhydramine-containing products are required,” noting that the safety of children was a big concern of the Canadian public.

On March 1 of this year, Health Canada posted a summary of that safety review, which focused on whether there have been any increases in frequency of the known side effects associated with oral, over-the-counter diphenhydramine in children under two years old or an increase in frequency of overdoses in children under 18.

“There are no new safety concerns to warrant regulatory action at this time,” Health Canada stated in the monthly Health Product InfoWatch.

Flanders believes that one of the factors driving Benadryl’s enduring ubiquity in the minds of Canadians is because it’s available so easily.

“I think it would make sense to take Benadryl off the list of over-the-counter allergy medications, because just there are better options and there are side effects and those can have long term implications,” he said.

“And that might be a nice way to sort of educate or to leave the general public with no choice but to choose a more appropriate medication.”

In 2019, some pharmacists pointed out that putting Benadryl behind the counter doesn’t solve the safety issues, and could cause conflict if customers are still pushing for it.

Nardine Nakhla, a pharmacist who teaches at the University of Waterloo in Ontario, said at the time that there are many other products that contain diphenhydramine that are on the shelves, making it unrealistic to pull all of them, and that there are other products available over the counter that have safety concerns, making this a complicated problem.

IF I HAVE BENADRYL AT HOME, SHOULD I KEEP USING IT FOR MYSELF OR MY KIDS?

For CSACI, it’s pretty straightforward.

“It is strongly encouraged that parents replace older first generation antihistamines such as Benadryl in their medicine cabinets with newer generation antihistamines,” it stated.

Flanders said that his advice depends on a family’s budget.

“If the purchase was made and there isn’t much money in the budget and there’s really bad allergy symptoms that need to be controlled, then Benadryl will do the trick, so I think it’s reasonable to complete the package,” he said. “And then next time you need it, buy the newer generation antihistamine.”

But if the cost of replacing the Benadryl immediately isn’t a concern, “then I would go right ahead and buy the new one and throw out the Benadryl, because there’s better options,” he said.

CSACI’s position statement pertained to all ages, but Flanders said that as a pediatrician, he is more concerned about making sure that children are receiving the best medication for whatever ails them.

“I think there’s an added dimension of risk for children because they’re still developing and they’re still in a very formative period of their lives. So if a child is chronically sleep deprived, I think there are more dire long term consequences,” he said, referring to side effects for Benadryl pertaining to poor sleep.

“For kids who are going to be taking it on a regular basis, it does interfere with the quality of their sleep and it can interfere with learning and with their sort of day to day functioning. It’s not like it’s the end of the world if you take Benadryl periodically for allergy relief, it’s just, there’s better options.”

WHICH NEWER ANTIHISTAMINES ARE PREFERRED?

CSACI gave CTVNews.ca a list of newer antihistamines currently available in Canada that it recommends over first-generation antihistamines:

• 
  bilastine (Blexten)
• 
  cetirizine (Reactine)
• 
  desloratadine (Aerius)
• 
  fexofenadine (Allegra)
• 
  loratadine (Claritin)
• 
  rupatadine (Rupall)

“Many of these are available over-the-counter, some of which are also available as generic preparations, and others are only available by prescription,” CSACI stated.  

ANTIHISTAMINS: from diphenhydramine to telfast | #03/01

Historically, the term “antihistamines” means drugs that block H1-histamine receptors, and drugs that act on H2-histamine receptors (cimetidine, ranitidine, famotidine, etc.) are called H2-histamine blockers. The former are used to treat allergic diseases, the latter are used as antisecretory agents.

Histamine, this most important mediator of various physiological and pathological processes in the body, was chemically synthesized in 1907 year. Subsequently, it was isolated from animal and human tissues (Windaus A., Vogt W.). Even later, its functions were determined: gastric secretion, neurotransmitter function in the central nervous system, allergic reactions, inflammation, etc. Almost 20 years later, in 1936, the first substances with antihistamine activity were created (Bovet D., Staub A.). And already in the 60s, the heterogeneity of histamine receptors in the body was proven and three of their subtypes were identified: H1, H2 and H3, differing in structure, localization and physiological effects that occur during their activation and blockade. Since that time, an active period of synthesis and clinical testing of various antihistamines begins.

Numerous studies have shown that histamine, acting on the receptors of the respiratory system, eyes and skin, causes characteristic allergy symptoms, and antihistamines that selectively block H1-type receptors can prevent and stop them.

Most of the antihistamines used have a number of specific pharmacological properties that characterize them as a separate group. These include the following effects: antipruritic, decongestant, antispastic, anticholinergic, antiserotonin, sedative and local anesthetic, as well as the prevention of histamine-induced bronchospasm. Some of them are not due to histamine blockade, but to structural features.

Antihistamines block the action of histamine on H1 receptors by the mechanism of competitive inhibition, and their affinity for these receptors is much lower than that of histamine. Therefore, these drugs are not able to displace histamine bound to the receptor, they only block unoccupied or released receptors. Accordingly, H1 blockers are most effective in preventing immediate allergic reactions, and in the case of a developed reaction, they prevent the release of new portions of histamine.

According to their chemical structure, most of them are fat-soluble amines, which have a similar structure. The core (R1) is represented by an aromatic and/or heterocyclic group and is linked via a nitrogen, oxygen or carbon (X) molecule to the amino group. The core determines the severity of antihistamine activity and some of the properties of the substance. Knowing its composition, one can predict the strength of the drug and its effects, such as the ability to penetrate the blood-brain barrier.

There are several classifications of antihistamines, although none of them is generally accepted. According to one of the most popular classifications, antihistamines are divided into first and second generation drugs according to the time of creation. First-generation drugs are also called sedatives (according to the dominant side effect), in contrast to non-sedative second-generation drugs. At present, it is customary to isolate the third generation: it includes fundamentally new drugs – active metabolites that, in addition to the highest antihistamine activity, exhibit the absence of a sedative effect and the cardiotoxic effect characteristic of second-generation drugs (see table).

In addition, according to the chemical structure (depending on the X-bond), antihistamines are divided into several groups (ethanolamines, ethylenediamines, alkylamines, derivatives of alphacarboline, quinuclidine, phenothiazine, piperazine and piperidine).

First generation antihistamines (sedatives). All of them are well soluble in fats and, in addition to H1-histamine, also block cholinergic, muscarinic and serotonin receptors. Being competitive blockers, they reversibly bind to H1 receptors, which leads to the use of rather high doses. The following pharmacological properties are most characteristic of them.

• Sedative effect is determined by the fact that most of the first generation antihistamines, being easily dissolved in lipids, penetrate well through the blood-brain barrier and bind to the H1-receptors of the brain. Perhaps their sedative effect consists of blocking the central serotonin and acetylcholine receptors. The degree of manifestation of the sedative effect of the first generation varies in different drugs and in different patients from moderate to severe and increases when combined with alcohol and psychotropic drugs. Some of them are used as sleeping pills (doxylamine). Rarely, instead of sedation, psychomotor agitation occurs (more often in medium therapeutic doses in children and in high toxic doses in adults). Due to the sedative effect, most drugs should not be used during tasks that require attention. All first-generation drugs potentiate the action of sedative and hypnotic drugs, narcotic and non-narcotic analgesics, monoamine oxidase inhibitors and alcohol.
• The anxiolytic effect characteristic of hydroxyzine may be due to the suppression of activity in certain areas of the subcortical region of the CNS.
• Atropine-like reactions associated with the anticholinergic properties of drugs are most characteristic of ethanolamines and ethylenediamines. Manifested by dry mouth and nasopharynx, urinary retention, constipation, tachycardia and visual impairment. These properties ensure the effectiveness of the discussed remedies in non-allergic rhinitis. At the same time, they can increase obstruction in bronchial asthma (due to an increase in sputum viscosity), exacerbate glaucoma and lead to infravesical obstruction in prostate adenoma, etc.
• Antiemetic and antiswaying effects are also likely to be associated with the central anticholinergic effect of the drugs. Some antihistamines (diphenhydramine, promethazine, cyclizine, meclizine) reduce the stimulation of vestibular receptors and inhibit the function of the labyrinth, and therefore can be used for motion sickness.
• A number of H1-histamine blockers reduce the symptoms of parkinsonism, which is due to the central inhibition of the effects of acetylcholine.
• Antitussive action is most characteristic of diphenhydramine, it is realized through a direct action on the cough center in the medulla oblongata.
• The antiserotonin effect, which is primarily characteristic of cyproheptadine, determines its use in migraine.
• α1-blocking effect with peripheral vasodilation, especially inherent in phenothiazine antihistamines, can lead to a transient decrease in blood pressure in sensitive individuals.
• Local anesthetic (cocaine-like) action is characteristic of most antihistamines (due to a decrease in membrane permeability to sodium ions). Diphenhydramine and promethazine are stronger local anesthetics than novocaine. However, they have systemic quinidine-like effects, manifested by prolongation of the refractory phase and the development of ventricular tachycardia.
• Tachyphylaxis: decrease in antihistamine activity with long-term use, confirming the need for alternating drugs every 2-3 weeks.
• It should be noted that first-generation antihistamines differ from second-generation antihistamines in the short duration of exposure with a relatively rapid onset of clinical effect. Many of them are available in parenteral forms. All of the above, as well as low cost, determine the widespread use of antihistamines today.

Moreover, many of the qualities that were discussed allowed the “old” antihistamines to occupy their niche in the treatment of certain pathologies (migraine, sleep disorders, extrapyramidal disorders, anxiety, motion sickness, etc.) that are not associated with allergies. Many first-generation antihistamines are included in combination preparations used for colds, as sedatives, hypnotics, and other components.

The most commonly used are chloropyramine, diphenhydramine, clemastine, cyproheptadine, promethazine, phencarol, and hydroxyzine.

Chloropyramine (Suprastin) is one of the most widely used sedative antihistamines. It has significant antihistamine activity, peripheral anticholinergic and moderate antispasmodic action. Effective in most cases for the treatment of seasonal and year-round allergic rhinoconjunctivitis, angioedema, urticaria, atopic dermatitis, eczema, itching of various etiologies; in parenteral form – for the treatment of acute allergic conditions requiring emergency care. Provides a wide range of usable therapeutic doses. It does not accumulate in the blood serum, so it does not cause an overdose with prolonged use. Suprastin is characterized by a rapid onset of effect and short duration (including side effects). At the same time, chloropyramine can be combined with non-sedating H1-blockers in order to increase the duration of the antiallergic effect. Suprastin is currently one of the best-selling antihistamines in Russia. This is objectively related to the proven high efficiency, controllability of its clinical effect, the availability of various dosage forms, including injections, and low cost.

Diphenhydramine , best known in our country under the name diphenhydramine, is one of the first synthesized H1-blockers. It has a fairly high antihistamine activity and reduces the severity of allergic and pseudo-allergic reactions. Due to the significant anticholinergic effect, it has an antitussive, antiemetic effect and at the same time causes dry mucous membranes, urinary retention. Due to lipophilicity, diphenhydramine gives pronounced sedation and can be used as a hypnotic. It has a significant local anesthetic effect, as a result of which it is sometimes used as an alternative for intolerance to novocaine and lidocaine. Diphenhydramine is presented in various dosage forms, including for parenteral use, which determined its widespread use in emergency therapy. However, a significant range of side effects, unpredictability of consequences and effects on the central nervous system require increased attention in its application and, if possible, the use of alternative means.

Clemastine (tavegil) is a highly effective antihistamine similar in action to diphenhydramine. It has a high anticholinergic activity, but to a lesser extent penetrates the blood-brain barrier. It also exists in an injectable form, which can be used as an additional remedy for anaphylactic shock and angioedema, for the prevention and treatment of allergic and pseudo-allergic reactions. However, hypersensitivity to clemastine and other antihistamines with a similar chemical structure is known.

Cyproheptadine (peritol), along with antihistamine, has a significant antiserotonin effect. In this regard, it is mainly used in some forms of migraine, dumping syndrome, as an appetite enhancer, in anorexia of various origins. It is the drug of choice for cold urticaria.

Promethazine (pipolfen) – a pronounced effect on the central nervous system determined its use in Meniere’s syndrome, chorea, encephalitis, sea and air sickness, as an antiemetic. In anesthesiology, promethazine is used as a component of lytic mixtures to potentiate anesthesia.

Quifenadine (phencarol) – has less antihistamine activity than diphenhydramine, but is also characterized by less penetration through the blood-brain barrier, which determines the lower severity of its sedative properties. In addition, fenkarol not only blocks histamine H1 receptors, but also reduces the content of histamine in tissues. May be used in the development of tolerance to other sedative antihistamines.

Hydroxyzine (atarax) – despite the existing antihistamine activity, it is not used as an antiallergic agent. It is used as an anxiolytic, sedative, muscle relaxant and antipruritic agent.

Thus, first-generation antihistamines that affect both H1- and other receptors (serotonin, central and peripheral cholinergic receptors, a-adrenergic receptors) have different effects, which determined their use in a variety of conditions. But the severity of side effects does not allow us to consider them as drugs of first choice in the treatment of allergic diseases. The experience gained with their use has allowed the development of unidirectional drugs – the second generation of antihistamines.

Second generation antihistamines (non-sedating). Unlike the previous generation, they almost do not have sedative and anticholinergic effects, but differ in their selective action on H1 receptors. However, for them, a cardiotoxic effect was noted to varying degrees.

The following properties are the most common for them.

• High specificity and high affinity for H1 receptors with no effect on choline and serotonin receptors.
• Rapid onset of clinical effect and duration of action. Prolongation can be achieved due to high protein binding, accumulation of the drug and its metabolites in the body, and delayed elimination.
• Minimal sedation when using drugs at therapeutic doses. It is explained by the weak passage of the blood-brain barrier due to the peculiarities of the structure of these funds. Some particularly sensitive individuals may experience moderate drowsiness, which is rarely the reason for discontinuing the drug.
• No tachyphylaxis with long-term use.
• The ability to block the potassium channels of the heart muscle, which is associated with prolongation of the QT interval and cardiac arrhythmias. The risk of this side effect increases when antihistamines are combined with antifungals (ketoconazole and itraconazole), macrolides (erythromycin and clarithromycin), antidepressants (fluoxetine, sertraline and paroxetine), grapefruit juice, and in patients with severe liver dysfunction.
• No parenteral formulations, but some (azelastine, levocabastine, bamipine) are available as topical formulations.

Below are second-generation antihistamines with their most characteristic properties.

Terfenadine is the first antihistamine drug without CNS depressant action. Its creation in 1977 was the result of a study of both the types of histamine receptors and the features of the structure and action of existing H1-blockers, and laid the foundation for the development of a new generation of antihistamines. Currently, terfenadine is used less and less, which is associated with its increased ability to cause fatal arrhythmias associated with prolongation of the QT interval (torsade de pointes).

Astemizol is one of the longest-acting drugs of the group (the half-life of its active metabolite is up to 20 days). It is characterized by irreversible binding to H1 receptors. Virtually no sedative effect, does not interact with alcohol. Since astemizole has a delayed effect on the course of the disease, it is not advisable to use it in an acute process, but it may be justified in chronic allergic diseases. Since the drug has the ability to accumulate in the body, the risk of developing serious heart rhythm disturbances, sometimes fatal, increases. Due to these dangerous side effects, the sale of astemizole in the United States and some other countries has been suspended.

Acrivastine (semprex) is a drug with high antihistamine activity with minimal sedative and anticholinergic effects. A feature of its pharmacokinetics is a low level of metabolism and the absence of cumulation. Acrivastine is preferred in cases where there is no need for permanent antiallergic treatment due to the rapid onset of effect and short-term effect, which allows for a flexible dosing regimen.

Dimetendene (Fenistil) is the closest to the first generation antihistamines, but differs from them in a significantly less pronounced sedative and muscarinic effect, higher antiallergic activity and duration of action.

Loratadin (Claritin) is one of the most purchased second-generation drugs, which is quite understandable and logical. Its antihistamine activity is higher than that of astemizole and terfenadine, due to the greater strength of binding to peripheral H1 receptors. The drug is devoid of a sedative effect and does not potentiate the effect of alcohol. In addition, loratadine practically does not interact with other drugs and does not have a cardiotoxic effect.

The following antihistamines are topical preparations and are intended to relieve local manifestations of allergies.

Levocabastin (Histimet) is used as an eye drop for the treatment of histamine-dependent allergic conjunctivitis or as a spray for allergic rhinitis. When applied topically, it enters the systemic circulation in a small amount and does not have undesirable effects on the central nervous and cardiovascular systems.

Azelastine (Allergodil) is a highly effective treatment for allergic rhinitis and conjunctivitis. Used as a nasal spray and eye drops, azelastine has little to no systemic effects.

Another topical antihistamine, bamipine (soventol), in the form of a gel, is intended for use in allergic skin lesions accompanied by itching, insect bites, jellyfish burns, frostbite, sunburn, and mild thermal burns.

Third generation antihistamines (metabolites). Their fundamental difference is that they are active metabolites of antihistamines of the previous generation. Their main feature is the inability to influence the QT interval. Currently, there are two drugs – cetirizine and fexofenadine.

Cetirizine (Zyrtec) is a highly selective peripheral H1 receptor antagonist. It is an active metabolite of hydroxyzine, which has a much less pronounced sedative effect. Cetirizine is almost not metabolized in the body, and the rate of its excretion depends on the function of the kidneys. Its characteristic feature is its high ability to penetrate the skin and, accordingly, its effectiveness in skin manifestations of allergies. Cetirizine neither experimentally nor in the clinic showed any arrhythmogenic effect on the heart, which predetermined the area of ​​practical use of metabolite drugs and determined the creation of a new drug, fexofenadine.

Fexofenadine (telfast) is the active metabolite of terfenadine. Fexofenadine does not undergo transformations in the body and its kinetics does not change with impaired liver and kidney function. It does not enter into any drug interactions, does not have a sedative effect and does not affect psychomotor activity. In this regard, the drug is approved for use by persons whose activities require increased attention. A study of the effect of fexofenadine on the QT value showed, both in the experiment and in the clinic, the complete absence of a cardiotropic effect when using high doses and with long-term use. Along with maximum safety, this remedy demonstrates the ability to stop symptoms in the treatment of seasonal allergic rhinitis and chronic idiopathic urticaria. Thus, the pharmacokinetics, safety profile and high clinical efficacy make fexofenadine the most promising of the antihistamines at present.

So, in the doctor’s arsenal there is a sufficient amount of antihistamines with different properties. It must be remembered that they provide only symptomatic relief from allergies. In addition, depending on the specific situation, you can use both different drugs and their diverse forms. It is also important for the physician to be aware of the safety of antihistamines.

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Taking Benadryl during pregnancy: is it safe? – Health

Video: Antihistamines are the main allergy medicines. How to choose?

Contents

• Why do people take Benadryl during pregnancy?
• Safety of Benadryl during pregnancy
• What about the first trimester?
• Possible harm to baby
• Side effects for mother
• Alternatives to Benadryl
• Conclusion

It’s allergy season (which sometimes seems to be all year round) and you scratch, sneeze, cough and watery eyes all the time. You are also pregnant, which can make runny nose and other allergy symptoms worse.

So, is it safe to take an allergy medicine like Benadryl on your oven bun?

More than 90 percent of women take over-the-counter (OTC) or prescription drugs during pregnancy. But you’re right, double-checking all medications during pregnancy. Even some over-the-counter drugs can cause side effects or be harmful.

Luckily, doctors recommend taking Benadryl to deal with terrible allergies during pregnancy. It is approved by the Food and Drug Administration (FDA) for pregnant women.

But keep in mind that no medication during pregnancy is 100 percent safe. Take Benadryl only when you need it and exactly as directed by your doctor.

Why do people take Benadryl during pregnancy?

Benadryl is the brand name for the drug diphenhydramine (you may see this chemical name on generic brands). This is an antihistamine. This means it helps calm your immune system from overreacting to pollen, dust, cats, and other allergens.

Taking Benadryl can relieve symptoms of allergies, asthma, hay fever and colds, such as:

• itchy eyes, nose or throat
• runny nose
• sneezing
• coughing
• congestion
• watery eyes
• pruritus
• skin rash

This over-the-counter medicine is also used to stop or relieve dizziness, nausea, and vomiting caused by car or sea disease. Since it can cause drowsiness, some women also use it to relieve insomnia during pregnancy.

Safety of Benadryl during Pregnancy

You are not the only one who wants to get rid of allergies when you are pregnant. Up to 15 percent of women in the US report taking antihistamines such as Benadryl during pregnancy. Medical research indicates that Benadryl is most likely safe for your growing child.

The Centers for Disease Control and Prevention reports that Benadryl is in a group of antihistamines called H₁. This group has been verified by many studies and found to be safe during pregnancy.

Other well-known allergy medications in this family of antihistamines include Claritin and Zyrtec. Doxylamine, another H₁ antihistamine commonly used for insomnia during pregnancy, is considered safe. You can recognize it by the Unisom trademark.

Another type of allergy antihistamine is called H₂. This species has been tested by fewer medical studies and may not be safe during pregnancy. OTC antihistamines in this group include Pepcid, Zantac, and Tagamet and should only be used under medical supervision.

What about the first trimester?

Be careful throughout pregnancy, especially in the first trimester. It’s an exciting time – when you haven’t even started showing yet – when a lot of the action is happening behind the scenes.

Although by 12 weeks your little beans will only be about 3 inches long, in the first trimester they will have developed all their major organ systems – heart, brain, lungs and everything.

This also makes the first 12 weeks of pregnancy the most dangerous. During the first trimester, your baby is most vulnerable to harm from alcohol, drugs, illness, and medication.

The Slone Center Birth Defect Study interviewed nearly 51,000 mothers over a period of approximately 40 years. It provided safety assessments for drugs that were commonly used during pregnancy. The highest rating a drug can have is “good” and the lowest rating is “no”.

This large study gave diphenhydramine a high “satisfactory” rating. For this reason, your doctor will likely advise you to only take Benadryl if you absolutely need it during the first trimester of your pregnancy.

This may be because older studies (some decades old) have shown that Benadryl can cause birth defects. More recent research has not shown this to be the case.

Possible harm to the child

As mentioned, some early studies reported that taking Benadryl and other drugs with diphenhydramine could cause birth abnormalities. These include cleft lip, cleft palate, and other problems associated with the development of the upper mouth and lower nose.

However, several recent medical studies have shown that diphenhydramine does not cause these or any birth abnormalities at all. This study shows that taking Benadryl at any stage of pregnancy, even in the first trimester, is safe.

Side effects for mom

Benadryl is a drug and can still cause the usual side effects in anyone. You may be more sensitive to Benadryl during pregnancy than usual.

Take Benadryl sparingly. Try less than the recommended dose to see if you no longer need it. It’s also worth noting that once your baby is born, you’ll be able to pass Benadryl through your breast milk, so it’s a good idea to get into the habit of eating less now.

Common side effects of Benadryl:

• drowsiness
• headache
• dry mouth and nose
• dry throat

Less common side effects of Benadry la who can still hit a brick wall during pregnancy include:

• nausea
• vomiting
• dizziness
• constipation
• chest congestion
• anxiety

Alternatives to Benadryl

If you usually take Benadryl for allergy relief or for sleep, there are natural alternatives that can help you.

Try these pregnancy-safe home remedies to help relieve allergy symptoms:

• using saline nasal drops
• using saline eye drops
• rinsing the nostrils with sterile water
• applying petroleum jelly (Vaseline) around the opening of the nostrils
• salt water gargle for sore throat

Always consult your doctor before taking any supplement, especially during pregnancy. You may ask about:

• locally produced pasteurized honey
• probiotics
• pregnancy safe, low mercury fish oil supplements

Natural remedies to make you sleepy include:

90 023 lavender essential oil
• chamomile essential oil
• bedtime meditation
• warm milk

Conclusion

Benadryl is considered safe during pregnancy.