Hematologic effects reported (e.g. neutropenia, leukopenia, thrombocytopenia, pancytopenia, and anemias). Dermatologic reactions (including toxic epidermal necrolysis and Stevens-Johnson syndromes), although rarely reported, resulted in fatalities (Asian patients with variant HLA-B*1502 may be at increased risk). Acute hepatotoxicity associated with hypersensitivity syndrome characterized by fever, skin eruptions, and lymphadenopathy reported. Osteomalacia reported. Use with caution in sinus bradycardia, SA block, or AV block, in hepatic impairment, and in any condition associated with low serum albumin levels, which will increase free fraction of phenytoin in serum and, therefore, pharmacologic response. Use with caution in porphyria. May increase frequency of petit mal seizures. Effects with other sedative drugs or ethanol may be potentiated. Use with caution in debilitated patients, and in the elderly. Intravenous form may cause hypotension, skin necrosis at intravenous site. Avoid I.V. administration in small veins. Sedation, confusional states, or cerebellar dysfunction (loss of motor coordination) may occur at higher total serum concentrations, or at lower total serum concentrations when free fraction of phenytoin is increased. Anticonvulsants should not be discontinued abruptly.