NAPLEX Practice Question # 25

NAPLEX Examination.

Practice Question # 25.




Carbamazepine (Tegretol) (NAPLEX Review)

Mechanisms of action.

Carbamazepine is chemically related to tricyclic antidepressants. Its mechanism of action is unknown in the treatment of seizure disorders, but it is thought to act by reducing polysynaptic responses and blocking the posttetanic potentiation.

Administration and dosage

(1) Adults and children  12 years of age receive an initial oral dose of 200 mg twice daily. This may be increased gradually to 800 to 1200 mg daily (usually given in divided doses).

(2) Children  12 usually receive 10 to 35 mg/kg daily in two or three divided doses.

Precautions and monitoring ef ects

(1) Carbamazepine should be used with caution in patients with bone marrow depression. ACBC should be obtained and platelets measured to determine baseline levels before therapy, and levels should be monitored during therapy. Aplastic anemia and agranulocytosis have been reported.

(2) Tricyclic antidepressants should be avoided if there is a history of hypersensitivity to tricyclics. Monoamine oxidase (MAO) inhibitors should be discontinued 2 weeks before carbamazepine therapy.

(3) Carbamazepine should be used cautiously in patients with glaucoma because of its mild anticholinergic eff ects that may result in increase of intraocular pressure.

(4) Carbamazepine is an enzyme inducer; therefore, the half-life (t½) decreases over 3 to 4 weeks (t½ 18 to 54 hrs; t½ 10 to 25 hrs); for maximal enzyme induction, levels should be rechecked to avoid breakthrough seizures.

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