Acts in the motor cortex of the brain to reduce the spread of electrical discharges from the rapidly firing epileptic foci in this area. This is accomplished by stabilizing hyperexcitable cells possibly by affecting sodium efflux. Also, phenytoin decreases activity of centers in the brain stem responsible for the tonic phase of grand mal seizures. Has few sedative effects. Monitor serum levels because the serum concentrations of phenytoin increase disproportionately as the dosage is increased.
Absorption is variable following PO dosage.
Since the rate and extent of absorption depend on the particular preparation, the same product should be used for a particular client. Biotransformed in the liver. Both inactive metabolites and unchanged drug are excreted in the urine. As an antiarrhythmic, phenytoin increases the electrical stimulation threshold of heart muscle, although it is less effective than quinidine, procainamide, or lidocaine. Chronic epilepsy, especially of the tonic-clonic, psychomotor type.