Description
Phenytoin Tablets IP 100 mg contain Phenytoin Sodium, a well-established antiepileptic drug used to manage and prevent various types of seizures. Classified as a hydantoin derivative, phenytoin works by stabilizing neuronal membranes and reducing repetitive firing by blocking voltage-gated sodium channels in the brain. This action helps in controlling generalized tonic-clonic (grand mal) seizures, focal (partial) seizures, and prevents post-traumatic seizures following neurosurgery or head injury.
Mechanism of Action: Phenytoin selectively binds to and inhibits voltage-gated sodium channels in neurons, which prevents sustained high-frequency firing of action potentials. This stabilizes hyperexcitable neuronal membranes and limits the spread of seizure activity without affecting normal neuronal transmission.
Therapeutic Uses:
- Treatment of tonic-clonic and focal seizures (simple or complex partial seizures)
- Prevention of seizures following neurosurgery or traumatic brain injury
- Management of status epilepticus (usually administered initially via IV, followed by oral maintenance)
- Occasionally used in neuropathic pain and certain arrhythmias, off-label
Pharmacokinetics:
- Absorption: Variable oral absorption (~70–100%)
- Protein Binding: Highly bound (~90–95%) to plasma albumin
- Metabolism: Liver (CYP2C9 and CYP2C19 enzymes)
- Half-life: 10 to 22 hours (dose-dependent; follows non-linear kinetics)
- Excretion: Primarily via urine as inactive metabolites
