Pharmacology - Chapter Forty-Five
A patient who takes valproic acid for a seizure disorder is preparing to have surgery. The primary care NP should order: a- coagulation studies. b- a complete blood count. c- an EEG. d- a creatinine clearance test.
a- coagulation studies. Valproic acid may cause thrombocytopenia and inhibition of platelet aggregation. Platelet counts and coagulation studies should be done before therapy is initiated, at regular intervals, and before any surgical procedure is performed.
A patient who takes carbamazepine (Tegretol) for a seizure disorder is seen by a primary care NP for a routine physical examination. A complete blood count (CBC) reveals a low white blood cell (WBC) count. The NP should: a- order a WBC differential. b- discontinue the carbamazepine. c- reassure the patient that this effect is temporary. d- decrease the carbamazepine dose and recheck the CBC in 2 weeks.
a- order a WBC differential. A benign leukopenia associated with carbamazepine is common and is reversible and dose-related. A WBC differential should be performed before changing the drug regimen.
A patient who takes carbamazepine (Tegretol) has been seizure-free for 2 years and asks the primary care NP about stopping the medication. The NP should: a- order an electroencephalogram (EEG). b- prescribe a tapering regimen of the drug. c- inform the patient that antiepileptic drug (AED) therapy is lifelong. d- tell the patient to stop the drug and use only as needed.
a- order an electroencephalogram (EEG). Discontinuation of AEDs may be considered in patients who have been seizure-free for longer than 2 years. An EEG should be obtained before the medication is withdrawn. The drug should be tapered to prevent status epilepticus, but only after a normal EEG is obtained. AED therapy is not lifelong in all patients. Patients should not stop AED medications abruptly, and these drugs are not used on an as-needed basis.
A patient is newly diagnosed with generalized epilepsy. The primary care NP will refer this patient to a neurologist and should expect this patient to begin taking: a- phenytoin (Dilantin). b- topiramate (Topamax). c- lamotrigine (Lamictal). d- levetiracetam (Keppra).
a- phenytoin (Dilantin). There is little good-quality evidence to support the use of newer monotherapy over older drugs. Phenytoin is the prototype of many seizure medications and is usually tried first. Other drugs may be used if seizures are resistant to phenytoin or if side effects occur.
A 20-kg child takes valproic acid (Depakote) for seizures and has had regular dose increases with a current dose of 250 mg twice daily. The child continues to have one to two seizures each week along with significant drowsiness that interferes with school participation. The primary care NP should contact the child's neurologist to discuss: a- obtaining a serum valproic acid level. b- changing the medication to gabapentin (Neurontin). c- increasing the valproic acid by 5 mg per kg of weight. d- adding lamotrigine (Lamictal) to this child's drug regimen.
d- adding lamotrigine (Lamictal) to this child's drug regimen Research suggests a combination of lamotrigine and valproate to be the most effective regimen in patients with refractory epilepsy. Valproic acid dosing may be increased to a maximum of 60 mg/kg/day unless side effects prevent further increase in dosage. The other drugs are not recommended.
A patient who has partial seizures has been taking phenytoin (Dilantin). The patient has recently developed thrombocytopenia. The primary care nurse practitioner (NP) should contact the patient's neurologist to discuss changing the patient's medication to: a- topiramate (Topamax). b- levetiracetam (Keppra). c- zonisamide (Zonegran). d- carbamazepine (Tegretol).
d- carbamazepine (Tegretol). Evidence-based recommendations exist showing carbamazepine to be effective as monotherapy for partial seizures. Because this patient has developed a serious side effect of phenytoin, changing to carbamazepine may be a good option. The other three drugs may be added to phenytoin or another first-line drug when drug-resistant seizures occur, but are not recommended as monotherapy.
A patient who is taking phenytoin (Dilantin) for a newly diagnosed seizure disorder calls the primary care NP to report a rash. The NP should: a- order a phenytoin level. b- reassure the patient that this is a self-limiting adverse effect. c- recommend that the patient take diphenhydramine to treat this side effect. d- tell the patient to stop taking the phenytoin and contact the neurologist immediately.
d- tell the patient to stop taking the phenytoin and contact the neurologist immediately. Phenytoin should be discontinued if skin rash appears because some rashes can be life-threatening. Rashes are not related to serum drug levels, so a phenytoin level is not indicated. Although some rashes are self-limiting, the patient should stop taking the drug until serious rashes are ruled out. Suggesting diphenhydramine is not correct until the severity of the rash is known.
A 12-month-old child with severe developmental delays was recently treated in an emergency department for a febrile seizure and is seen by the primary care NP for a follow-up visit. The child's parent asks if it is necessary to continue giving the child phenobarbital. The NP should tell the parent that: a- the phenobarbital may be used on an as-needed basis. b- the phenobarbital may be stopped when an EEG is normal. c- once the febrile illness is past, the phenobarbital may be stopped. d- their child is at increased risk for seizures and should continue the phenobarbital.
d- their child is at increased risk for seizures and should continue the phenobarbital. Although the American Academy of Pediatrics has concluded that the risks of long-term treatment with phenobarbital outweigh the potential benefits in most cases, continued treatment with this drug is used in children at greatest risk for future neurologic problems, including children with febrile seizures before 18 months of age and children with neurologic dysfunction or severe developmental delays.