NAPLEX Practice Question # 32
NAPLEX Examination.
Practice Question # 32.
Naplex
Phenobarbital (Luminal)
Mechanism of action.
Phenobarbital increases the seizure threshold by decreasing postsynaptic excitation by stimulating postsynaptic GABA-A receptor inhibitor responses as a CNS depressant.
Administration and dosage
- For adults, phenobarbital is administered orally at 90 to 300 mg daily (in three divided doses or as a single dose at bedtime).
- Children typically receive 3 to 6 mg/kg daily in two divided doses. Adjustment is made as needed.
Adverse effects.
The physician should be notifi ed if any of the following adverse effects occur: sore throat, mouth sores, easy bruising or bleeding, and any signs of infection.
- CNS eff ects include agitation, confusion, lethargy, and drowsiness. Patients should avoid alcohol and other CNS depressants.
- Respiratory eff ects include hypoventilation and apnea.
- Cardiovascular eff ects include bradycardia and hypotension.
- GI eff ects include nausea, diarrhea, and constipation. If GI upset is experienced, phenobarbital should be taken with food.
- Hematological eff ects include megaloblastic anemia aft er chronic use (a rare side effect).
- Miscellaneous eff ects include osteomalacia and Stevens–Johnson syndrome, both of which are rare.