Therapeutic Study. Do you take acetaminophen, aspirin, carbamazepine (anti-epileptic), digoxin (anti-arrhythmic), phenytoin (ant-epileptic), valproic acid (anti-epileptic/mood stabilizer), or vancomycin (antibiotic)? You may qualify to participate in a clinical study at no cost to you. Compensation for time and travel may be available.