Risk of intracranial HTN w/ oral retinoids & vit A (>10,000 IU/day). May decrease absorption w/ Fe prep & antacids, Mg/Al & Ca hydroxides, oxides & salts, activated charcoal, cholestyramine, bismuth chelates & sucralfate. May reduce absorption of tetracycline w/ medicinal products which increase gastric pH. Enzyme inducers eg, barbiturates, carbamazepine, phenytoin may accelerate decomposition. Effect of oral coumarin-type anticoagulants could be increased w/ increased risk of haemorrhage. May interfere w/ bacteriocidal action of penicillin & β-lactam antibiotics. Fatal renal toxicity w/ methoxyflurane. Decreased digestive absorption due to increased gastric pH w/ didanosine. Increase in serum lithium levels.