What are phenobarbital side effects? 

Common side effects of phenobarbital are listed below. Tell your doctor if these adverse effects are severe or do not go away after a few days.

• Drowsiness
• Dizziness
• Headache
• Restlessness
• Nausea
• Vomiting
• Increased activity or excitement (particularly in children)

Phenobarbital can also cause more serious adverse reactions in a small number of people. Please call your doctor immediately if you experience:

• Slowed breathing or difficulty breathing (respiratory depression)
• Eyes, cheeks, lips, or tongue swelling
• Rash, itching, peeling skin
• Fever
• Confusion

The above list may not include all the potential adverse effects of phenobarbital. Contact your doctor if you have severe adverse effects or worsening symptoms. You can also report unusual side effects to the Food and Drug Administration at 1-800-FDA-1088.

Phenobarbital overdose: In case of a known or suspected overdose, get emergency medical help right away, call your local poison control center, or call the national poison helpline at 1-800-222-1222. Symptoms of a phenobarbital overdose or severe poisoning may include drowsiness, slowed breathing, respiratory arrest, uncontrolled eye movements, loss of coordination, skin blisters, skin pain, and lower body temperature.