Cevimeline in Treating Patients With Dry Mouth Caused by Radiation Therapy for Head and Neck Cancer

DISEASE CHARACTERISTICS: * Received more than 4,000 cGy of prior external beam radiotherapy for cancer in the head and neck region * Radiotherapy completed more than 4 months prior to study * Clinically significant salivary gland dysfunction with grade 2 or 3 xerostomia * At least 1 anatomically intact parotid gland * No suspected or confirmed bilateral physical closure of salivary gland ducts * No history of primary or secondary Sjogren's syndrome or other underlying systemic illness known to cause xerostomia independent of prior radiotherapy exposure PATIENT CHARACTERISTICS: Age: * 18 and over Performance status: * Karnofsky 70-100% * ECOG 0-2 Life expectancy: * At least 6 months Hematopoietic: * Hemoglobin at least 9.0 g/dL * No anemia Hepatic: * Bilirubin no greater than 2 times upper limit of normal (ULN) * SGOT/SGPT no greater than 2 times ULN * Lactate dehydrogenase no greater than 2 times ULN * No evidence of active liver disease Renal: * Creatinine no greater than 2.5 mg/dL * BUN no greater than 50 mg/dL * No history of nephrolithiasis within the past 6 months Cardiovascular: * No history of significant cardiovascular disease * No active congestive heart failure * No uncontrolled angina * No significant arrhythmia * No myocardial infarction within the past 6 months Pulmonary: * No history of significant pulmonary disease * No controlled or uncontrolled asthma * No chronic bronchitis or chronic obstructive pulmonary disease that would limit avocational activities Gastrointestinal: * No history of significant gastrointestinal disorder * No active pancreatic disease * No gastroduodenal ulcers within the past 6 months * No hypersensitive bowel conditions requiring pharmacologic therapy * No inflammatory bowel disease * No history of cholelithiasis within the past 6 months (unless cholecystectomy performed) Other: * No clinically significant laboratory abnormality * No history of alcohol or drug abuse within the past 6 months that would preclude study * No prior or concurrent acute iritis or narrow-angle (angle closure) glaucoma * Not pregnant * Negative pregnancy test * Fertile patients must use effective contraception PRIOR CONCURRENT THERAPY: Biologic therapy: * Not specified Chemotherapy: * No concurrent chemotherapy Endocrine therapy: * Not specified Radiotherapy: * See Disease Characteristics * No concurrent radiotherapy Surgery: * Not specified Other: * At least 30 days since other investigational new drug * At least 4 weeks since prior systemic or ophthalmic pilocarpine * No prior cevimeline * No concurrent hyperbaric oxygen therapy * No concurrent beta adrenergic antagonists, anticholinergic agents, cevimeline metabolism inhibitors, or other medications known to effect salivary function * No other concurrent investigational drugs