A nurse is reviewing the medication history of a client who has been taking phenobarbital (Luminal) for generalized seizures. The client reports feeling tired and depressed most of the time. What is an appropriate response by the nurse?

Carbamazepine is an anticonvulsant that works by stabilizing the neuronal membrane and preventing the spread of seizure activity¹. One of the common side effects of carbamazepine is drowsiness or dizziness, which may affect your ability to drive or operate machinery. You should avoid alcohol and other sedatives while taking this medication, and be careful when getting up from a lying or sitting position².

Choice B. You should avoid grapefruit juice while taking this medication is also correct. Grapefruit juice can interact with carbamazepine and increase its blood levels, which may increase the risk of toxicity and adverse effects. You should avoid drinking grapefruit juice or eating grapefruit while taking this medication, unless your doctor tells you otherwise³⁴.

Choice C. You should have your blood pressure checked regularly while taking this medication is wrong because carbamazepine does not affect blood pressure significantly. However, you should have your blood counts checked regularly while taking this medication, as carbamazepine can cause serious blood disorders such as aplastic anemia and agranulocytosis. You should also have your liver function tests and thyroid function tests monitored periodically, as carbamazepine can cause liver damage and thyroid abnormalities².

Choice D. You should report any signs of bleeding or bruising to your provider is also correct. Carbamazepine can interact with warfarin and other anticoagulants and increase the risk of bleeding by inhibiting the metabolism of warfarin and displacing it from plasma protein binding sites⁵. You should report any signs of bleeding or bruising to your provider, and have your INR and PT checked regularly if you are taking warfarin or other anticoagulants with carbamazepine.

Choice E. You should use a reliable form of contraception while taking this medication is also correct. Carbamazepine can reduce the effectiveness of hormonal contraceptives such as the pill, the implant, the patch, the vaginal ring, and the emergency contraceptive pill by inducing the liver enzyme CYP450, which breaks down estrogen and progesterone faster. This could put you at risk of an unplanned pregnancy. You should use a reliable form of non-hormonal contraception such as condoms or an intrauterine device (IUD) while taking this medication, unless your doctor advises you otherwise²⁶.

Phenytoin is an anticonvulsant that works by stabilizing the neuronal membrane and preventing the spread of seizure activity¹. The therapeutic range of phenytoin is **10-20 mcg/mL**²³⁴⁵. A serum phenytoin level of **25 mcg/mL** is above the therapeutic range and indicates toxicity. The nurse should hold the next dose and notify the provider to prevent further adverse effects, such as nystagmus, ataxia, confusion, and coma¹.

Choice A. Administer the next dose as scheduled is wrong because it would increase the risk of phenytoin toxicity and worsen the client's condition.

Choice C. Increase the next dose by 25% is wrong because it would also increase the risk of phenytoin toxicity and worsen the client's condition.

Choice D. Decrease the next dose by 25% is wrong because it may not be enough to lower the phenytoin level to the therapeutic range. The nurse should consult with the provider before making any dose adjustments.