Health Guide

Phenobarbital (By injection)

Phenobarbital (fee-noe-BAR-bi-tal)

Treats seizures and epilepsy. Also used to relieve tension, anxiety, and insomnia.

Brand Name(s):

There may be other brand names for this medicine.

When This Medicine Should Not Be Used:

This medicine is not right for everyone. You should not use it if you had an allergic reaction to phenobarbital or to other barbiturate drugs. Do not use this medicine if you are pregnant, or if you have a history of porphyria.

How to Use This Medicine:


  • A nurse or other healthcare provider will give you this medicine through a needle placed into your vein or a shot into your muscle.

Drugs and Foods to Avoid:

Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.

  • Some medicines can affect how phenobarbital works. Tell your doctor if you are using phenytoin, disulfiram, an MAO inhibitor (MAOI), valproic acid, digitoxin, steroid medicine, doxycycline, griseofulvin, sodium valproate, or a blood thinner (such as warfarin).
  • Birth control pills may not work as well while you use this medicine. You may want to use a second form of birth control.
  • Do not drink alcohol. This medicine can intensify the effects of alcohol or any other medicine that makes you sleepy, such as allergy medicine.

Warnings While Using This Medicine:

  • It is not safe to take this medicine during pregnancy. It could harm an unborn baby. Tell your doctor right away if you become pregnant.
  • Tell your doctor if you are breastfeeding or have liver disease. Also tell him if you have ever had depression, thoughts about suicide, or a drug addiction.
  • This medicine can be habit-forming. Do not use more than your prescribed dose. Call your doctor if you think your medicine is not working.
  • Do not stop using this medicine suddenly. Your doctor will need to slowly decrease your dose before you stop it completely.
  • This medicine may make you dizzy or drowsy. Do not drive or use machines until you know how this medicine affects you.

Possible Side Effects While Using This Medicine:

Call your doctor right away if you notice any of these side effects:

  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
  • Extreme lightheadedness or fainting
  • Redness, pain, or swelling where the shot was given
  • Severe confusion, drowsiness, or muscle weakness
  • Severe nausea or vomiting
  • Slurred speech, trouble walking, or tremors

If you notice other side effects that you think are caused by this medicine, tell your doctor

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088

Last Updated: 6/18/2019
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