McKenna's Pharmacology for Nursing, 2e

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C H A P T E R 2 3 Antiseizure agents

DRUGS FOR TREATING PARTIAL SEIZURES Partial seizures may be simple (involving only a single muscle or reaction) or complex (involving a series of reac­ tions or emotional changes). Drugs used in the treatment of partial seizures include carbamazepine ( Tegretol , Teril ), gabapentin ( Neurontin ), lacosamide ( Vimpat ), lamotrigine ( Lamictal ), levetiracetam ( Keppra ), oxcar­ bazepine ( Trileptal ), pregabalin ( Lyrica ), tiagabine ( Gabitril ) and topiramate ( Topamax ) (see Table 23.3). Some of the drugs used to treat generalised seizures have also been found to be useful in treating partial seizures (see Table 23.1). • Fatigue, weakness, and drowsiness: Try to space activities evenly throughout the day and allow rest periods to avoid these effects. Take safety precautions and avoid driving or operating dangerous machinery if these conditions occur. • Headaches and difficulty sleeping: These usually disappear as your body adjusts to the drug. If they persist Monitor for adverse effects: CNS effects (multiple); bone marrow suppression; rash, skin changes; GI effects— nausea, anorexia; arrhythmias. Monitor for drug–drug interactions: increased depression with CNS depressants, alcohol; drugs as listed. Evaluate effectiveness of teaching program. Evaluate effectiveness of comfort/safety measures. Teaching for J.M. • The drugs that are being evaluated for you are called antiepileptic agents. They are used to stabilise abnormal cells in the brain that have been firing excessively and causing seizures. • The timing of these doses is very important. To be effective, this drug must be taken regularly. • Do not stop taking this drug suddenly. If for any reason you are unable to continue taking the drug, notify your healthcare provider at once. This drug must be slowly withdrawn when its use is discontinued. • Common effects of these drugs include:

Therapeutic actions and indications The drugs used to control partial seizures stabilise nerve membranes in either of two ways—directly, by altering sodium and calcium channels, or indirectly, by increasing the activity of GABA, an inhibitory neuro­ transmitter, and thereby decreasing excessive activity (see Figure 23.2). Carbamazepine and oxcarbazepine are used as monotherapy, and the remaining drugs are used as adjunctive therapy (see Table 23.3 for usual indications for each agent). Each of the drugs used for treating partial seizures has a slightly different mech­ anism of action. Carbamazepine is chemically related to the tricyclic antidepressants. It has the ability to inhibit polysynaptic responses and to block sodium channels to prevent the formation of repetitive action potentials in the abnormal focus. Gabapentin ( Neurontin ) inhibits polysynaptic responses and blocks stimulus increases in certain situ­ ations. However, the mechanism by which gabapentin exerts its anticonvulsant action is unknown. Gabapen­ tin is structurally related to the neurotransmitter GABA (gamma-aminobutyric acid) but its mechanism of action is different from that of several other medications that interact with GABA synapses including valproate, and become too uncomfortable, consult with your healthcare provider. • Gastrointestinal upset, loss of appetite, and diarrhoea or constipation: Taking the drug with food or eating small, frequent meals may help alleviate this problem. • Report any of the following conditions to your healthcare provider: skin rash, severe nausea and vomiting, impaired coordination, yellowing of the eyes or skin, fever, sore throat, personality changes, and unusual bleeding or bruising . • It is advisable to wear or carry a Medic-Alert warning so that any person who takes care of you in an emergency will know that you are taking this drug. • Tell any doctor, nurse or other healthcare provider involved in your care that you are taking this drug. • Keep this drug and all medications out of the reach of children. • Do not take any other drug, including over-the-counter medications and alcohol, without consulting with your healthcare provider. Many of these preparations interact with the drug and could cause adverse effects. • Report and record any seizure activity that you have while you are taking this drug. • Take this drug exactly as prescribed. Regular medical follow-up, which may include blood tests, will be necessary to evaluate the effects of this drug on your body.

Safe medication administration

Name confusion has been reported between Keppra (levetiracetam) and Kaletra (lopinavir/ritonavir), an HIV antiviral combination drug. Both drugs come in a liquid form, and confusion has been reported in the administration of the two drugs, causing serious adverse effects. Use extreme caution when administering these drugs.