What is phenobarbital?
Phenobarbital is in a group of drugs called barbiturates (bar-BIT-chur-ates). Phenobarbital
slows the activity of your brain and nervous system.
Phenobarbital is used to treat or prevent seizures. It is also used short-term to treat
insomnia, or as a sedative before surgery.
Phenobarbital may also be used for other purposes not listed in this medication guide.
What should I discuss with my healthcare provider before taking phenobarbital?
Some people using this medicine have engaged in activity such as driving,
eating, or making phone calls and later having no memory of the activity.
If this
happens to you, stop taking phenobarbital and talk with your doctor about another treatment for
your sleep disorder.
Do not take this medication if you are allergic to phenobarbital, or if you have
porphyria.
Before taking phenobarbital, tell your doctor if you are allergic to any drugs, or if you
have:
-
severe asthma, chronic obstructive pulmonary disorder (COPD),
or other breathing disorder;
-
liver disease;
-
kidney disease;
-
an adrenal gland disorder, such as pheochromocytoma;
-
a history of depression, mental illness, or suicide attempt;
or
-
a history of drug or alcohol addiction.
If you have any of these conditions, you may need a dose adjustment
or special tests to safely take phenobarbital.
Phenobarbital may be habit-forming and
should be used only by the person
it was prescribed for
. Phenobarbital should never be shared with another person,
especially someone who has a history of drug abuse or addiction. Keep the medication in a
secure place where others cannot get to it.
Do not
use this medication without telling your doctor if you are
pregnant. It could cause harm to the unborn baby. Use an effective form of birth control, and tell
your doctor if you become pregnant during treatment.
Phenobarbital can make birth control pills less effective. Ask your doctor about using
a non-hormone method of birth control (such as a condom, diaphragm, spermicide) to prevent
pregnancy while taking phenobarbital.
Phenobarbital can pass into breast milk and may harm a nursing baby. Do not use
this medication without telling your doctor if you are breast-feeding a baby.
How should I take phenobarbital?
Take this medication exactly as it was prescribed for you. Do not take the medication in
larger amounts, or take it for longer than recommended by your doctor. Follow the directions on
your prescription label.
Take phenobarbital only when you are getting ready for several hours
of sleep.
You may fall asleep very quickly after taking the medicine.
Take this medicine with a full glass of water.
Measure the liquid form of phenobarbital with a special dose-measuring spoon or cup, not
a regular table spoon. If you do not have a dose-measuring device, ask your pharmacist for one.
If you are taking this medicine to treat insomnia, take it only at bedtime. Do not use
phenobarbital for longer than 2 weeks to treat insomnia, unless your doctor has told you to.
Do not change your dose of phenobarbital without your doctor's advice. Tell your doctor
if the medication does not seem to work as well in treating your condition.
If you are taking phenobarbital to treat seizures, keep taking the medication even if
you feel fine. You may have increased seizures or withdrawal symptoms if you stop using
phenobarbital suddenly. You will need to use less and less before you stop the medication
completely.
Store phenobarbital at room temperature away from moisture and heat.
Keep track of how many pills have been used from each new bottle of this medicine.
Phenobarbital is a drug of abuse and you should be aware if any person in the household is using
this medicine improperly or without a prescription.
What happens if I miss a dose of phenobarbital?
Take the missed dose as soon as you remember. If it is almost time for your next dose,
skip the missed dose and take the medicine at your next regularly scheduled time.
Do
not
take extra medicine to make up the missed dose.
Where can I get more information about phenobarbital?
Your pharmacist has information about phenobarbital written for health professionals that you may read.
What are the possible side effects of phenobarbital?
Phenobarbital may cause a severe allergic reaction.
Stop taking
phenobarbital and get emergency medical help if you have any of these
signs of an
allergic reaction
: hives; difficulty breathing; swelling of your face, lips, tongue, or
throat.
Call your doctor at once if you have any of these serious side effects:
-
restless muscle movements in your eyes, tongue, jaw, or neck;
-
slow heartbeat, shallow breathing;
-
feeling light-headed, fainting;
-
a fever or a sore throat;
-
sores in your mouth;
-
easy bruising or bleeding; or
-
broken blood vessels under your skin.
Less serious side effects may include:
-
drowsiness or dizziness;
-
problems with memory or concentration;
-
excitement, irritability, aggression, or confusion (especially
in children or older adults);
-
loss of balance or coordination;
-
nausea, constipation;
-
headache; or
-
"hangover" effect (drowsiness the day after a dose).
This is not a complete list of side effects and others may occur. Tell
your doctor about any unusual or bothersome side effect. You may report side effects to FDA at 1-800-FDA-1088.
What is the most important information I should know about phenobarbital?
Phenobarbital may cause a severe allergic reaction.
Stop taking
phenobarbital and get emergency medical help if you have any of these
signs of an
allergic reaction
: hives; difficulty breathing; swelling of your face, lips, tongue, or
throat.
Do not stop using phenobarbital without first talking to your doctor, even if you feel
better. You may have increased seizures if you stop using phenobarbital suddenly. You will
need to use less and less before you stop the medication completely.
Take phenobarbital only when you are getting ready for several hours
of sleep.
You may fall asleep very quickly after taking the medicine.
Some people using this medicine have engaged in activity such as driving,
eating, or making phone calls and later having no memory of the activity.
If this
happens to you, stop taking phenobarbital and talk with your doctor about another treatment for
your sleep disorder.
Do not
use phenobarbital without telling your doctor if you are
pregnant. It could cause harm to the unborn baby. Use an effective form of birth control, and tell
your doctor if you become pregnant during treatment.
Phenobarbital can make birth control pills less effective. Ask your doctor about
using a non-hormone method of birth control (such as a condom, diaphragm, spermicide) to
prevent pregnancy while taking phenobarbital.
Phenobarbital may be habit-forming and
should be used only by the person
it was prescribed for
. Phenobarbital should never be shared with another person,
especially someone who has a history of drug abuse or addiction. Keep the medication in a
secure place where others cannot get to it.
What should I avoid while taking phenobarbital?
Phenobarbital can cause side effects that may impair your thinking or reactions. Be
careful if you drive or do anything that requires you to be awake and alert.
Avoid using other medicines that make you sleepy (such as cold medicine, sleeping pills,
pain medication, muscle relaxers, and medicine to treat depression or anxiety). They can add to
sleepiness caused by phenobarbital.
Avoid drinking alcohol. It can increase some of the side effects of phenobarbital.
What other drugs will affect phenobarbital?
Before taking phenobarbital, tell your doctor if you are using any of the following drugs:
-
doxycycline (Adoxa, Doryx, Mondox, Oracea, Vibramycin, and
others);
-
other seizure medications such as divalproex (Depakote),
phenytoin (Dilantin), or valproic acid (Depakene);
-
an MAO inhibitor such as isocarboxazid (Marplan),
phenelzine (Nardil), rasagiline (Azilect), selegiline (Eldepryl, Emsam), or tranylcypromine
(Parnate);
-
griseofulvin (Grisactin, Fulvicin PG, Grifulvin V);
-
birth control pills or estrogen hormone replacement,
including estrogen (Premarin), estradiol (Estrace, Femtrace, and others), progesterone (Progest,
Prometrium), and others;
-
steroids such as prednisone (Orasone, Deltasone),
prednisolone (Prelone, Delta Cortef), methylprednisolone (Medrol), and others.
This is not a complete list and there may be other drugs that can
interact with phenobarbital. Tell your doctor about all the prescription and over-the-counter
medications you use. This includes vitamins, minerals, herbal products, and drugs prescribed by
other doctors. Do not start using a new medication without telling your doctor.
What happens if I have an overdose of phenobarbital?