Does gabapentin cause weight gain? What are the changes in body weight with chronic, high-dose gabapentin therapy? Explore the findings from a research study on the effects of prophylactic gabapentin on weight loss and narcotic dependency in patients with oropharyngeal cancer undergoing radiation therapy.

Prophylactic Gabapentin Linked to Weight Loss and Narcotic Dependency Reduction

Researchers from Scottsdale, Arizona presented findings at the 2016 Multidisciplinary Head and Neck Cancer Symposium, which showed that patients with oropharyngeal cancer undergoing radiation therapy experienced diminished narcotic dependency and weight loss when given prophylactic gabapentin at a dose of 300 mg 3 times daily (TID).

Pain and weight loss are common side effects of radiation therapy in patients with head and neck cancer, and although narcotic pain medication (NPM) is often used, these medications come with their own side effects such as nausea, constipation, and respiratory depression. Furthermore, neuropathic pain often responds poorly to NPM, requiring escalating doses for pain relief.

Evaluating Ideal Dosages of Prophylactic Gabapentin

As part of a retrospective chart review, researchers sought to determine the ideal dose of prophylactic gabapentin needed to reduce weight loss and narcotic dependency among patients with oropharyngeal cancer undergoing radiation therapy with or without chemotherapy.

The study included 64 patients who had completed their prescribed radiation therapy courses and had at least 1 month of post-radiation therapy follow-up. Of these, 31 patients received prophylactic gabapentin (≥300 mg TID) within the first 2 weeks of radiotherapy, while 33 patients did not receive prophylactic gabapentin.

Less Weight Loss with Prophylactic Gabapentin Use

The researchers found that patients with oropharyngeal cancer who initiated ≥300 mg TID of prophylactic gabapentin within the first 2 weeks of radiotherapy experienced less unintentional weight loss and initiated NPM later in their radiation therapy course compared to patients who were not treated with prophylactic gabapentin. However, total NPM use was not diminished in patients who received prophylactic gabapentin.

Collectively, the prophylactic gabapentin group had 47% less weight loss than the retrospective control group (4.10 kg vs 9.02 kg, P <.01). The effect of prophylactic gabapentin was not influenced by oropharyngeal subsite and p16 status, and no adverse effects were attributed to its use.

Subgroup Analysis: Benefits of Prophylactic Gabapentin

Patients who underwent upfront surgery and those with p16-positive disease saw the most benefit from prophylactic gabapentin use. The surgery group given prophylactic gabapentin had 68.5% less weight loss than the untreated group (2.40 kg vs 7.63 kg, P = .02), and the p16-positive group receiving prophylactic gabapentin showed 60% less weight loss than their untreated counterparts (3.61 kg vs 9.02 kg; P = .004).

Limitations and Future Directions

The researchers acknowledge that the study did not elucidate a direct diminishment in overall NPM requirement with the addition of prophylactic gabapentin, which they attribute to the low number of patients and the retrospective nature of the investigation. They assert that the data support continued exploration of prophylactic gabapentin use to delay the use of or serve as an adjunct to standard NPM regimens in this patient population.

The researchers state that their institution intends to further explore the impact of higher prophylactic gabapentin dosing and timing and its impact on feeding tube use and quality of life metrics.

Conclusion

The study findings suggest that prophylactic gabapentin use in patients with oropharyngeal cancer undergoing radiation therapy can lead to reduced weight loss, particularly in those who have undergone upfront surgery or have p16-positive disease. However, the study did not find a direct reduction in overall narcotic pain medication use. Further research is needed to fully elucidate the potential benefits of prophylactic gabapentin in this patient population.