Anticonvulsants are used to control seizure activity and prevent seizures. Anticonvulsants are given IV to control acute seizures, and they are given orally to prevent seizures. The mechanism of action of each anticonvulsant is specific to the drug. Still, anticonvulsants work primarily by preventing the epileptic cells in the brain from depolarizing and initiating a seizure (Katzung et al., Chapter 24, 2021d).
Anticonvulsants available as an IV preparation are listed in Table 3.
Table 3: Anticonvulsants| Generic Name | Brand Name |
|---|
| Lacosamide | Vimpat® |
| Levetiracetam | Keppra® |
| Phenobarbital | Generic only |
| Phenytoin | Dilantin® |
| Valproic acid | Depakote® |
There are a few adverse effects that are common to all IV anticonvulsants, such as central nervous system (CNS) depression. Administration issues and adverse effects of individual anticonvulsants are described next; administration issues and adverse effects common to all the anticonvulsants will be discussed later.
Lacosamide: Lacosamide should be infused over 30 to 60 minutes, but if needed, a 15-minute infusion duration is acceptable (UCB Pharmaceuticals, 2022b). A diluted preparation of lacosamide should not be stored at room temperature for > 4 hours. Common adverse effects are dizziness, headache, nausea, and somnolence (UCB Pharmaceuticals, 2022b). IV lacosamide can cause bradycardia, ECG changes, and arrhythmias. If the patient has a cardiac condition, an ECG should be done before starting therapy and when the maintenance dose has been established (UCB Pharmaceuticals, 2022b).
Levetiracetam: Levetiracetam should be infused in over 15 minutes (UCB Pharmaceuticals, 2022a). A diluted solution of levetiracetam should be stored at room temperature and be used within 4 hours (UCB Pharmaceuticals, 2022a). Common adverse effects of levetiracetam include asthenia (lack of energy, weakness), hypertension, behavioral abnormalities such as aggression, psychotic signs/symptoms, and abnormal blood counts (UCB Pharmaceuticals, 2022a).
Phenobarbital: IV phenobarbital can cause hypotension and respiratory depression (Doshi et al., 2019; Pugin et al., 2014; Hocker et al., 2018).
Phenytoin: Hypotension, arrhythmias, and other adverse cardiac effects can happen if IV phenytoin is given faster than the recommended infusion rate (Guldiken et al., 2014; Smollin, 2018; UpToDate, 2022h). Use a slower infusion rate that is less than the maximum 50 mg/minute for elderly patients or those who have a cardiac condition, and closely monitor their blood pressure and heart rate (Guldiken et al., 2014; UpToDate, 2022h). Neurological adverse effects of phenytoin include mild CNS depression, fatigue, and nystagmus (Farrokh et al., 2018). If the serum level is abnormally high, ataxia, incoordination, slurred speech, and seizures can occur (Farrokh et al., 2018; Smollin, 2018). A diluted solution should be used within 4 hours.
Extravasation of IV phenytoin can cause purple glove syndrome (Perez Del Nogal et al., 2022; Garbovsky et al., 2015). Purple glove syndrome is characterized by edema, pain, discolored skin, and in severe cases, compartment syndrome, tissue ischemia, and necrosis (Perez Del Nogal et al., 2022; Garbovsky et al., 2015). Purple glove syndrome can happen with the first infusion of phenytoin and can occur without extravasation (Garbovsky et al., 2015; Perez Del Nogal et al., 2022). If extravasation with phenytoin happens, the IV infusion should be stopped immediately (Garbovsky et al., 2015; UpToDate, 2022h).
Valproic acid: IV valproic should be infused over 60 minutes. The prescribing information for valproic acid has a black box warning: “Hepatic failure resulting in fatalities has occurred in patients receiving valproate. These incidents usually occur during the first six months of treatment. Serious or fatal hepatotoxicity may be preceded by nonspecific symptoms such as malaise, weakness, lethargy, facial edema, anorexia, and vomiting.” (UpToDate, 2022g). A black box warning means that a drug can cause a severe adverse effect, and nurses should be aware of this adverse effect (Livertox, 2020b). A high serum ammonia level is one of the causes of liver damage from valproic acid, and ammonia levels should be periodically measured (Livertox, 2020b). Drowsiness and thrombocytopenia are common adverse effects of valproic acid (Buoli et al., 2018; Duman et al., 2019).
Administration issues and adverse effects of anticonvulsants include:
- Blood levels: Blood levels of phenobarbital, phenytoin, and valproic acid are periodically measured, and the dose will be adjusted depending on the level (Kanner & Bicchi, 2022). For these drugs, nurses should know subtherapeutic and toxicity levels. Blood levels of levetiracetam can be done, and they may be useful, depending on the patient and the situation (Sourbron et al. 2018). Blood levels of all the anticonvulsants can be measured to determine the correct dose or if a low or a high blood level is causing an adverse effect, to see how a dose change affects the level, and to make sure that the dose is appropriate for a specific age group of patients, such as children and the elderly, or for people who have medical conditions like hepatic and/or renal impairment (Patsalos et al., 2018; Sourbron et al., 2018).
- Suicide: Anticonvulsant use has been associated with an increased risk for suicide, which is mentioned in the prescribing information for these drugs (Mula, 2022).
- Rate of infusion: Adverse effects can occur if an IV anticonvulsant is administered too quickly.
- Withdrawal seizures: Anticonvulsants must be slowly tapered to prevent withdrawal seizures (Gloss et al., 2021; Loro et al., 2022).
