Antiepileptics: Nursing pharmacology

Antiepileptics, also known as anticonvulsants, are medications primarily used to treat epilepsy, as well as generalized or partial seizures.

On rare occasions, these medications can be used to treat mood disorders. Now, the most commonly used antiepileptics can be subdivided, based on their mechanism of action, into four main groups: sodium channel blockers, calcium channel blockers, GABA inhibitors, and GABA analogues.

In addition, other medications can be used as antiepileptics, including barbiturates like phenobarbital and benzodiazepines like diazepam, which are primarily used as anxiolytics and sedative-hypnotics.Now, let’s focus on sodium channel blockers first.

These medications work by blocking voltage-gated sodium channels, eventually inhibiting excitatory neurons from firing action potentials.

Decreased activity of excitatory neurons results in the reduction and alleviation of seizures. Sodium channel blockers include hydantoins, iminostilbene derivatives, valproate derivatives, and lamotrigine.First, let’s focus on hydantoins.

These medications include phenytoin, which can be administered orally or intravenously; and its prodrug, fosphenytoin, which can be administered intravenously or intramuscularly.

Common side effects of these medications include headaches, dizziness, visual disturbances, such as blurred vision, nystagmus, and diplopia, as well as gingival hyperplasia.

Some clients might experience hypersensitivity reactions like Stevens-Johnson syndrome and toxic epidermal necrolysis, as well as drug reactions with eosinophilia and systemic symptoms or DRESS for short.In addition, these medications can cause hepatotoxicity, as well as impaired metabolism of vitamin D, which can result in osteomalacia.

Moreover, these medications can impair the absorption of folic acid and vitamin B12; this can lead to hematologic side effects, often referred to as blood dyscrasias, such as agranulocytosis, leukopenia, thrombocytopenia, and anemia.

As a boxed warning, rapid IV administration can result in hypotension and cardiac arrhythmias. Finally, a very important side effect is suicidal thoughts.

As far as contraindications go, phenytoin should be avoided during pregnancy, as well as in clients with sinus bradycardia, heart block, and Adams-Stokes syndrome, which refers to a condition characterized by syncopal episodes caused by cardiac arrhythmias.The next group of sodium channel blockers covers iminostilbene derivatives, such as carbamazepine, which can be administered orally or intravenously.

Important side effects include pancreatitis, hepatotoxicity, and renal dysfunction which could result in fluid retention and hyponatremia, as well as cardiovascular side effects, such as hypertension and AV block.

In addition, carbamazepine has boxed warnings for severe side effects, including Stevens-Johnson syndrome, toxic epidermal necrolysis, and DRESS, as well as bone marrow depression, which can result in blood dyscrasias.

Now, carbamazepine should not be administered within 14 days of monoamine oxidase inhibitors, or concomitantly with non-nucleoside reverse transcriptase inhibitors that are CYP3A4 substrates, such as nefazodone.

Finally carbamazepine is contraindicated during pregnancy, and should be used with caution in clients who are breastfeeding, as well as in those with alcoholism, cardiac, hepatic, or renal disease, and in children younger than 6 years of age.The next group includes valproate derivative forms, called valproic acid and sodium valproate, which can be administered orally and intravenously.

Now, in addition to working as sodium channel blockers, these medications can increase the concentration of gamma-aminobutyric acid, or GABA for short, which is one of the main inhibitory neurotransmitters in the brain.

Ultimately, this results in decreased seizure activity. The most common side effects are gastrointestinal problems, such as dyspepsia, nausea, vomiting, diarrhea, and constipation.

Some clients might also experience hematologic side effects, like thrombocytopenia and leukopenia; while others can develop DRESS.

In addition, valproate can cause suicidal thoughts, as well as central nervous system depression or even coma. Finally, it’s important to note that valproate has boxed warnings for pancreatitis and hepatotoxicity, as well as regarding fetal toxicity, since valproate may result in congenital malformations, especially neural tube defects.

For that reason, valproate is contraindicated during pregnancy. In addition, it should be avoided in clients with urea cycle disorders, mitochondrial disease, or hepatic disease.The last sodium channel blocker is lamotrigine, which is taken orally.

The most common side effects include headache, dizziness, and dysmenorrhea. On rare occasions, lamotrigine can also cause more severe side effects, such as suicidal thoughts, and hematologic side effects, including disseminated intravascular coagulation, leukopenia, and thrombocytopenia.

Also, lamotrigine has a boxed warning for causing serious and potentially life-threatening skin rash, as well as Stevens-Johnson syndrome and toxic epidermal necrolysis.

Now, lamotrigine must not be stopped abruptly, since clients may present with uncontrolled seizures. In addition, this medication should be used with caution during pregnancy and breastfeeding, as well as in clients with severe depression, and in clients younger than 16 or elderly.

Finally, precaution should be taken in clients with cardiac disease, such as heart failure or conduction disorders like second or third degree heart block, as well as in clients with hepatic or renal disease.

The next group of antiepileptics is calcium channel blockers. These medications work by blocking voltage-gated calcium channels, subsequently inhibiting excitatory neurons from firing action potentials, and ultimately decreasing seizure activity.

First, let’s start with succinimides, more specifically ethosuximide, which is taken orally. The most common side effects include gastrointestinal problems, such as nausea, vomiting, and diarrhea.

Some clients might also complain of headaches, fatigue, and pruritus; while others might even develop blood dyscrasias or hypersensitivity skin reactions like DRESS.

Finally, these medications should be used with caution during pregnancy and breastfeeding, as well as in clients with hepatic or renal disease.

Another important medication is levetiracetam, which can be administered orally or intravenously. The exact mechanism of action of levetiracetam is not fully understood, but it’s thought to act as a calcium channel blocker.

Important side effects associated with levetiracetam include suicidal thoughts, Stevens-Johnson syndrome, as well as toxic epidermal necrolysis.

Some clients can also develop hepatitis.Finally, this medication is contraindicated in clients who are breastfeeding, and should be used with caution during pregnancy, as well as in pediatric or elderly clients, and those with cardiac, hepatic, or renal disease.

The next group of antiepileptics are GABA inhibitors. The most commonly used medication in this group is vigabatrin, which is taken orally.

Once administered, vigabatrin acts on presynaptic neurons by inhibiting the reuptake of GABA, which is an inhibitory neurotransmitter.

As a result, there’s an increased concentration of free GABA in the synaptic cleft, which helps control the seizure. The most common side effects associated with vigabatrin include dizziness, gastrointestinal problems, weight gain, and edema.

Additional side effects include a decrease in hemoglobin and hematocrit, as well as peripheral neuropathy, usually involving the toes and feet.

Vigabatrin can cause some life-threatening side effects, including suicidal thoughts, malignant hyperthermia, respiratory depression, and even pulmonary embolism.

In addition, vigabatrin has a boxed warning for visual impairment! Regarding contraindications, this medication should be used with caution during pregnancy and breastfeeding, as well as in children younger than 2 years or elderly clients.

Finally, precaution should be taken in clients with hepatic or renal disease, as well as in those with a history of psychosis or depression.

The last group of antiepileptics are GABA analogues like gabapentin, which can be administered orally. Although the exact mechanism of action is unclear, gabapentin is structurally similar to GABA, so it may exert an inhibitory effect that ultimately helps control the seizure.Unfortunately, this inhibitory effect may cause side effects like depression, amnesia, somnolence, and ataxia.

Gabapentin may also cause blurred vision, nystagmus, diplopia, and dry mouth; as well as gastrointestinal side effects like increased appetite, nausea, vomiting, and diarrhea or constipation.

Finally, some clients might experience cough, pruritus, hypersensitivity reactions like DRESS, and may develop leukopenia.Important precautions should be taken during pregnancy and breastfeeding, as well as in children younger than 3 years old or elderly clients.

In addition, gabapentin should be used with caution in clients experiencing suicidal thoughts, depression, and those with renal disease or undergoing hemodialysis.

Now, before beginning antiepileptic therapy, review your client’s medical record to determine the type of seizures they experience, how often the seizures occur, and how long the seizures typically last.

In addition, check their history for conditions such as depression, and screen for suicidal thoughts. Then, review the laboratory test results, such as CBC, as well as liver and renal function tests.

Next, for any client prescribed phenytoin, carbamazepine, or lamotrigine, be sure to review recent diagnostic tests like ECG; and if your client is prescribed vigabatrin, obtain a baseline vision test as well.

For clients of child-bearing age, confirm a negative pregnancy test, and stress the importance of using reliable contraception while taking an antiepileptic medication.

Lastly, advise them to wear medical identification to assist diagnosis and treatment by emergency personnel.Be sure to teach your client how antiepileptics will help control their seizures.

Stress the importance of taking the medication exactly as prescribed and to never stop taking it abruptly, as this can increase the risk of breakthrough seizures.

Let them know that CNS depression can occur, so caution your client against consuming other CNS depressant medications or alcohol; and advise them to avoid activities that require alertness, such as driving, until they adjust to the medication’s effects.

Next, teach your client about side effects that should be reported to the healthcare provider immediately. Explain how anxiety, agitation, depression, or other changes in their mood or behavior could indicate an increased risk of suicidal behavior.

And let them know that liver dysfunction could manifest as symptoms such as anorexia, nausea, vomiting, and fatigue. Also be sure to describe signs of blood dyscrasias, such as fever, sore throat, pallor, weakness, petechiae, or easy bruising.

Lastly, prompt your client to keep a close eye on any changes in their skin, especially if an unusual rash develops. Now, if your client is prescribed phenytoin, teach them how to recognize signs of gingival hyperplasia such as sore, swollen gums; and explain how performing daily dental hygiene, taking a folic acid supplement, and regular visits to the dentist can decrease the risk.

Also explain how the risk of bone loss can be reduced by increasing dietary calcium and vitamin D as well as doing weight-bearing exercises as tolerated.

Lastly, advise your client to report visual disturbances, such as blurred vision, nystagmus, or diplopia.If your client is prescribed carbamazepine, instruct them to avoid grapefruit or grapefruit juice in order to decrease the risk of carbamazepine toxicity.

Also teach them to contact their healthcare provider right away if they notice symptoms of pancreatitis, such as upper abdominal pain, nausea and vomiting, or anorexia.

In addition, instruct them to report symptoms of water retention and hyponatremia like swelling, weight gain, headache, muscle weakness, or cramps.

Okay, if your client is prescribed vigabatrin, stress the importance of vision checks every 3 months during therapy, and instruct them to report any changes in their vision, such as blurred vision, difficulty controlling eye movements, or vision loss.

In addition, teach your client to report symptoms of peripheral neuropathy, such as a feeling of burning or numbness in their toes or feet.Finally, be sure to closely monitor your client for side effects by regularly monitoring your client’s mental status, mood, and behavior, as well as CBC, liver, and renal function tests during treatment.

Evaluate for therapeutic effects of a decrease in seizure frequency, severity, and duration. Alright, as a quick recap… Antiepileptics are medications that are used to treat seizures.

There are four main classes of antiepileptics: sodium channel blockers, calcium channel blockers, GABA inhibitors, and GABA analogues.

Sodium channel blockers suppress action potentials by blocking overactive voltage-gated sodium channels, while calcium channel blockers reduce seizure activity by blocking voltage-gated calcium channels.

GABA inhibitors inhibit the reuptake of GABA, an inhibitory neurotransmitter and thus increasing its availability in the synaptic cleft.

And GABA analogues are structurally similar to GABA. Side effects of antiepileptics include central nervous system depression, hepatotoxicity, blood dyscrasias, and suicidal thoughts.

Nursing considerations are focused on assessment before administration, client education about serious side effects, regular monitoring, as well as evaluating the effectiveness of treatment.