Anticonvulsant Therapy

Anticonvulsants, also known as antiepileptics, are medications primarily used to treat seizures and, on rare occasions, are prescribed to treat mood disorders. The most commonly prescribed anticonvulsant to manage seizures is phenytoin.

So seizures occur acutely due to abnormal, excessive, and synchronous firing of neurons in the brain, which manifests as a change in the patient's level of consciousness, body movements, sensations, or autonomic functions. Seizures usually last for a few seconds or minutes. When a patient has two or more seizures separated by at least 24 hours without a known cause, it is considered epilepsy.

Now, anticonvulsants are categorized by their mechanism of action in managing seizures, which include suppression of sodium influx, suppression of calcium influx, or enhancement of gamma-aminobutyric acid, or GABA. First let’s focus on medications like phenytoin and other hydantoins, that act by inhibiting sodium influx into neuronal cells, thereby stabilizing cell membranes and reducing repetitive neuronal firing.

Next, succinimide medications like ethosuximide work by blocking the calcium influx, preventing the electrical current generated by the calcium ions into the T-type calcium channel, ultimately reducing neuronal cell discharge. Lastly, medications like phenobarbital and benzodiazepines increase the action of GABA, which inhibits neurotransmitters throughout the brain to reduce seizure activity.

Alright, so common side effects of phenytoin include headaches, dizziness, and gingival hyperplasia. Some patients experience serious hypersensitivity reactions like Stevens-Johnson syndrome and toxic epidermal necrolysis. In addition, phenytoin can cause constipation and nausea, as well as impaired metabolism of vitamin D, which can result in osteomalacia.

Moreover, phenytoin can impair the absorption of folic acid and vitamin B-12; which can lead to hematologic side effects, referred to as blood dyscrasias, such as agranulocytosis, leukopenia, and anemia. Phenytoin also has a Black Box warning related to the development of hypotension and cardiac arrhythmias if the medication is administered by IV too rapidly. So, the medication should always be administered slowly, and cardiac monitoring should be in place before, during, and after administration. Finally, it’s important to note that phenytoin can cause suicidal thoughts.