Severe nutritional deficiencies decrease bioavailability. May lead to loose stool &/or diarrhea at start of treatment; discontinue treatment if unusually frequent liquid or watery stool is experienced. Dehydration & hypokalemia may occur during concomitant use w/ diuretics. Particular caution in case of hypokalemia during concomitant use w/ cardiac glycosides (eg, digitoxin, digoxin). Should not be taken concomitantly w/ laxatives, especially during the 1st 2-4 wk of treatment. May result in intense yellow urine coloration; increase in water intake is recommended. Comorbid conditions & past or concurrent liver disease; screen for major causes of active hepatic disease. Contraindicated in patients w/ severe liver disease. Monitor for signs of hepatic injury; caution in concomitant use w/ drugs associated w/ hepatic injury. Limit alcohol intake while on treatment. Discontinue if symptoms suggestive or liver damage arise (abdominal pain, jaundice, pruritus & increased liver enzyme). Severe renal insufficiency. Do not use during pregnancy & lactation. Not for childn <18 yr. Elderly ≥65 yr.