• 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.

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.

Where can I get more information?

Your pharmacist can provide more information about phenobarbital.

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.