Administration of phenytoin associated with atrial and ventricular conduction depression and ventricular fibrillation. Hematologic effects (e.g. neutropenia, leukopenia, thrombocytopenia, pancytopenia, and anemias) reported with use (patients with previous history of adverse hematologic reaction to any drug may be at increased risk). Severe dermatologic reactions (including toxic epidermal necrolysis and Stevens-Johnson syndromes), might occur, and may be fatal. Acute hepatotoxicity associated with a hypersensitivity syndrome characterized by fever, skin eruptions, and lymphadenopathy reported to occur within first 2 months of treatment. Hypotension might occur, especially after I.V. administration at high doses and high rates of administration. Use with caution in hypotension, diabetes mellitus, fever, hepatic impairment, hypoalbuminemia, hypothyroidism, porphyria, or renal impairment. Effects with other sedative drugs or ethanol may be potentiated.