PHENOBARBITAL
Indication:
Phenobarbital is useful in treating generalized (grand mal) seizures and some
simple partial seizures.
Possible side effects: Phenobarbital, especially in higher doses,
can produce lethargy, irritability, slurred speech and imbalance. These problems
usually improve after an adjustment in dosage. A hyperactivity-irritability syndrome
most often seen in children can occasionally be found in adults. Occasional problems
with shoulder stiffness or sexual impotency have been reported.
You need to know that any changes in your anticonvulsant therapy, there may be
an increase in seizure frequency. Keep in mind that side effects vary among individuals.
If you have any problems with the medication, you should let your doctor know
whether or not it is a problem listed above.
Dosage: Phenobarbital is supplied in white tablets of 16, 32,
65 and 100 mg. Phenobarbital elixir is also available. Most adult patients require
between 150 to 200 mg daily for seizure control. In some cases doses of 300 mg
or even more are well tolerated and provide good seizure control.
Drug interaction: Phenobarbital reduces the effect of antipyrine,
cimetidine, chlorpromazine, haloperidol, nortriptyline, bishydroxycoumarin and
warfarin. Valproic acid (Depakote) can increase phenobarbital accumulation which
can ultimately lower valproic acid levels. Phenytoin (Dilantin) can cause an elevation
in phenobarbital levels. Other drugs can affect or be affected by phenobarbitol.
Oral contraception: The efficacy of some birth control pills
can be affected by phenobarbital. In these cases phenobarbital can lower the estrogen
levels of the birth control pills. This can be remedied by taking a birth control
pill with a higher level of estrogen. Check with your doctor.
Blood levels: The usual blood levels for phenobarbital range
from 10 to 40 mcg/ml. If you are not having side effects your doctor may consider
using doses which result in higher blood levels.