Patient/caregiver was instructed upon therapeutic uses and mechanism of action of phenytoin as follows:
- Nerve impulses in the brain are transmitted from one cell to the other as mild electrical impulses.
- Many factors such as, neurotransmitters in the brain, sodium and glucose concentrations in the blood, bacterial infections, blood and oxygen supply to the brain, and mechanical injury to the brain play a significant role in influencing these nerve impulses in the brain.
- Some of these factors can act excitatory and some can act inhibitory to the nerve impulses in the brain. Excitatory factors can contribute to increased electrical discharge and nerve impulse transmission in the brain. Inhibitory factors can contribute to reduced electrical discharge and inhibition of nerve impulse transmission in the brain.
- Excitatory and inhibitory factors influencing the nerve impulse transmission in the brain are usually regulated in a fine balance. Disturbance to this fine balance due to any reason, favoring excitatory influence on the nerve impulse conduction in the brain, can result in excess electrical discharge in the brain, contributing to development of seizure activity.
- Voltage-gated sodium channels in the nerve cells, during activation of nerve impulse, allow significant sodium entry into the cells. Increased sodium concentration in the nerve cells is considered an important factor in increased excitation and consequent seizure activity.
- Phenytoin is an anticonvulsant medication, which blocks these sodium channels, thus inhibiting influx of sodium and reducing the sodium concentration in the nerve cell.
- Reduced sodium concentration in the nerve cells helps with reducing the excitation of nerve cells, controls the rapid firing of impulses, and blocks the excess electrical discharge, contributing to control of seizures. Phenytoin is used as an anticonvulsant agent in controlling tonic-clonic seizures.
- Phenytoin also blocks the sodium channels of the peripheral nerves, thus helping to reduce the excitation and conduction of nerve impulses along the nerves. This helps controlling the rapid firing of impulses in neuralgia and neuropathy, such as, in individuals with history of shingles.
- Phenytoin also blocks the sodium channels in the cardiac tissues, thus helping to reduce the excitation and controlling the rapid firing of cardiac impulses during arrhythmia and so, can be used as an anti-arrhythmic agent.
