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.

As far as contraindications go, phenytoin should be avoided during pregnancy due to its teratogenic properties. Additionally, phenytoin has a high incidence of interaction with other substances. For example, when combined with alcohol, phenytoin can cause central nervous system depression, or when taken with the herb evening primrose, it can lead to a decreased seizure threshold. Phenytoin should be used with caution in patients with cardiac disorders, especially bradycardia or second- or third-degree heart block. It should also be used with caution in patients with diabetes, since phenytoin can inhibit insulin release.

Alright, let's look at the nursing care you will provide to a patient receiving anticonvulsant therapy with phenytoin. Begin by instituting fall precautions, to prevent falls if drowsiness occurs. Then, review your patient's history for conditions such as depression, and monitor them for suicidal thoughts. Be sure to check their laboratory test results, including CBC, glucose, and liver and renal function tests, as well as a therapeutic serum phenytoin level between 10 to 20 mcg/mL. If the serum level is greater than 20 mcg/mL, report this to the health care provider immediately, and observe for early signs of toxicity, such as lethargy, muscular incoordination, visual disturbances like nystagmus and diplopia. Now, if your patient is receiving phenytoin IV, remember that phenytoin is a vesicant, so ensure the IV catheter is intact; place them on a cardiac monitor, watch their blood pressure closely, and infuse the medication slowly.

Alright, let's move on to patient teaching. Be sure to stress the importance of taking the medication as directed and to never abruptly stop therapy, as this can cause a sudden increase in seizure activity. Then, teach your patient how to recognize and respond to common side effects. Describe the signs and symptoms of gingival hyperplasia such as sore, swollen gums; and explain how performing daily dental hygiene, and regular visits to the dentist can decrease the risk. Let them know their urine may turn a pinkish or reddish-brown color, but this is an expected and harmless side effect. Also, teach your patient to avoid consuming alcohol; and to inform their health care provider if they plan to start a new medication or over-the-counter supplement.

If your patient has diabetes mellitus, advise them to monitor their glucose levels more closely than usual, since phenytoin can cause an increase in their glucose level. Lastly, advise your patient to contact their health care provider if they experience visual disturbances, such as blurred vision or diplopia; as well as a skin rash or signs of increased bleeding, such as excessive bruising or frequent nosebleeds. Lastly, for patients of child-bearing age, stress the importance of using reliable contraception while taking this medication to avoid teratogenic effects on the fetus.

Alright, as a quick recap... Anticonvulsants, also known as antiepileptics, are medications primarily used to treat seizures. There are three main classes of anticonvulsants which are categorized by their mechanisms of action, including suppression of sodium influx, suppression of calcium influx, and enhancement of GABA. Side effects of phenytoin include CNS depression, blood dyscrasias, and suicidal thoughts. It also has a Black Box warning related to the development of hypotension and cardiac arrhythmias if the medication is administered IV too rapidly. Nursing considerations are focused on assessment before, during, and after administration, and providing patient education about serious side effects.