A nurse is caring for a client who has been taking phenytoin (Dilantin) for partial seizures. The nurse notes that the client has a serum phenytoin level of 25 mcg/mL. What is the appropriate action 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.

Phenobarbital is a barbiturate that can cause physical and psychological dependence with chronic use, meaning that the body and the mind become accustomed to the drug and need it to function normally. Dependence can lead to withdrawal symptoms when the drug is stopped or reduced, such as insomnia, nausea, tremors, and dizziness⁹. Dependence can also increase the risk of overdose, tolerance, and addiction¹³.

Choice A is wrong because these are not common side effects of phenobarbital, but signs of dependence. Common side effects of phenobarbital may include drowsiness, lack of energy, dizziness, or spinning sensation².

Choice B is wrong because these are not signs of toxicity, but signs of dependence. Toxicity occurs when the drug reaches a level in the body that causes harmful effects, such as respiratory depression, hypotension, coma, or death⁵. Signs of toxicity may include slow or shallow breathing, weak pulse, cold or clammy skin, little or no urination, pinpoint pupils, feeling cold, or fainting².

Choice C is wrong because these are not symptoms of withdrawal, but signs of dependence. Withdrawal occurs when the drug is stopped or reduced after a period of regular use, causing the body and the mind to react to the absence of the drug. Withdrawal symptoms may include anxiety, restlessness, irritability, agitation, confusion, hallucinations, seizures, or delirium⁹. Increasing the dose of phenobarbital can worsen the dependence and increase the risk of adverse effects.