• Basic Info
• Top Questions
• Clinical Info
• Interactions

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.

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.