| Phenobarbital | Single loading dose of 15 to 20 mg/kg given orally, intravenously, or intramuscularly. If symptoms are still severe 8 to 12 hours after initial dose, the dose can be repeated once (total cumulative maximum loading of 40 mg/kg). | 3 to 4 mg/kg per day started 12 to 24 hours after initial dose Administered as a single dose in the evening OR two divided doses given every 12 hours Increase dose by 1 to 5 mg/kg per day until therapeutic plasma levels are achieved | Therapeutic goal of trough plasma concentration level between 20 and 30 mg/dL (86 and 129 micromoles/L), obtained 24 to 48 hours after initiation or change in dosing | Phenobarbital should be weaned after morphine is fully tapered off Taper phenobarbital dose to decrease drug concentration by 10 to 20 percent per day |
