Gabapentin for Mouth Pain from Head and Neck Cancer Treatment

Inclusion Criteria: * Histologic documentation of disease: Squamous cell carcinoma of the head and neck region. \* Stage: I-IV * No prior treatment for head and neck cancer * Planned treatment with cisplatin-based chemoradiation therapy (weekly or once every 3 weeks \[q 3 week\]) * Able to swallow capsules whole * No known hypersensitivity to gabapentin or its ingredients * No patients on dialysis or with transplanted organs * No prior surgery or radiation for head and neck cancer and/or are being treated for recurrent head and neck cancer. Patients with a history of surgery and radioactive iodine for the treatment of thyroid cancer are eligible. Concurrent cancer therapy for other cancers is not allowed * No planned surgery or chemotherapy or immunotherapy following 7 weeks of standard chemoradiation treatment * No known brain metastases * No nonprescribed use of any opioids (including heroin) within 6 months prior to registration * No prescribed medications for chronic and/or long-term pain and/or neuropathy, including patients under treatment of a pain specialist or substance abuse programs. Acute post-biopsy medications are allowed if the patient has discontinued them 3 days prior to study registration * No current treatment with mefloquine * Age ≥ 18 years * Eastern Cooperative Oncology Group (ECOG) performance status ≤ 2 * Creatinine ≤ 1.5 x upper limit of normal (ULN) * Not pregnant and not nursing, because this study involves both radiation and chemotherapy. In addition, the genotoxic, mutagenic and teratogenic effects on the developing fetus and newborn are unknown. Therefore, for women of childbearing potential, a negative pregnancy test done \< 7 days prior to registration is required. Women must agree to using contraception for the duration of receiving study drugs and for 6 months after completing chemoradiation * Not taking medications for a psychotic psychiatric illness * No existing diagnosis of sleep apnea * No acute narrow-angle glaucoma * No uncontrolled concurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements * No investigational agent within 30 days prior to registration * No enrollment on other studies of systemic pain control agents * Language: In order to complete the mandatory patient-completed measures, participants must be able to speak and read English or Spanish * Patients with impaired decision making are not eligible for study Exclusion Criteria: \-