--Drowsiness, sedation, lethargy, vertigo, nausea, vomiting, constipation, headache, fever, hypocalcemia, megaloblastic anemia, osteomalacia, rickets, confusion, ataxia, nystagmus, folate deficiency, respiratory depression, hypotension, bradycardia, syncope, allergic reactions, exfoliative dermatitis, lupus erythematosus syndrome, agranulocytosis, thrombocytopenia, hepatic dysfunction, renal dysfunction, dependence, withdrawal symptoms