Brand names: Barbita, Solfoton

Phenobarbital is a barbiturate and anticonvulsant. It acts is a depressant to the central nervous system. 

Quick Facts About Phenobarbital


Used to promote sleep and to treat certain types of epilepsy, including generalized or grand mal and partial seizures.

Phenobarbital Dosage

Take exactly as prescribed. If taking for seizures, do not suddenly stop taking medication. Adhere to dosage levels prescribed by doctor; never increase dose on your own. May become physically or psychologically dependent with continued use.

  • Usual adult dose: for sedation — a single dose of 30 to 120 milligrams, not to exceed 400 milligrams during a 24-hour period. For daytime sedation — 30 to 120 milligrams per day divided into 2 or 3 doses. To promote sleep — 100 to 200 milligrams at bedtime. For anticonvulsant use — must be individualized; usual range is from 60 to 200 milligrams per day. Seniors and those with liver or kidney disease — may be prescribed a lower dose.
  • Usual child dose: for anticonvulsant use — must be individualized. Usual dose is 3 to 6 milligrams per 2.2 pounds of body weight per day.
  • Missed dose: take as soon as possible, unless almost time for next dose. In that case, do not take missed dose; go back to regular schedule. Do not double doses.

Phenobarbital Side Effects

Overdose symptoms:

congestive heart failure, diminished breathing, extremely low body temperature, fluid in lungs, involuntary eyeball movements, irregular heartbeat, kidney failure, lack of muscle coordination, low blood pressure, poor reflexes, skin reddening or bloody blisters, slowdown of central nervous system. If you suspect an overdose, immediately seek medical attention.

Overdose may be fatal.

Side effects: abnormal thinking; aggravation of existing emotional disturbances and phobias; agitation: anemia; angioedema (swelling of face around lips, tongue, and throat, swollen arms and legs, difficulty breathing); allergic reactions (localized swelling of the eyelids, cheeks, or lips, skin redness and inflammation); anxiety; confusion; constipation; decreasec breathing; delirium; difficulty sleeping; dizziness; drowsiness; excitement; fainting; fever; hallucinations: headache; increased physical activity and muscle movement; irritability and hyperactivity in children; lack of muscle coordination; low blood pressure; muscle, nerve, or joint pain, especially in people with insomnia; nausea; nervousness; nightmares; psychiatric disturbances; rash; residual drowsiness; restlessness, excitement, and delirium when taken for pain; shallow breathing; sleepiness; slow heartbeat; slowdown of the nervous system; sluggishness; softening of bones; temporary cessation of breathing; vertigo; vomiting.

No known less common or rare Phenobarbital side effects.


Inform your doctor before combining Phenobarbital with:

all antidepressants, including Nardil, Elavil, and Prozac; narcotic pain relievers such as Demerol and Dilaudid; sedatives such as Seconal, Halcion, and Dalmane; tranquilizers such as Xanax and Valium.

Do not drink alcohol while taking phenobarbital. 

Special Cautions

If pregnant or planning to become pregnant, inform your doctor immediately. Appears in breast milk; could affect a nursing infant.

Seniors may be prescribed a lower dose. Can cause depression or confusion in seniors.

Follow doctor’s instructions carefully for children. May cause excitement in children.

  • May cause drowsiness and impair your ability to drive a car or operate machinery. Do not take part in any activity that requires alertness.
  • Inform your doctor before taking phenobarbital if you have pain or are in constant pain.
  • Should not use if you have porphyria (metabolic disorder), liver disease, or lung disease that causes breathing problems, or if sensitive to or allergic to phenobarbital or other barbiturates.
  • If you have a history of depression or drug abuse, use with extreme caution.
  • Can cause depression or confusion in those with weakened conditions.
  • Use with caution if you have liver disease or adrenal gland problems.

Note: provides accurate and independent information prescription pills, over-the-counter medicines and natural products. This material is provided for educational purposes only and is not intended for medical advice, diagnosis or treatment. If you have questions about  dosage, or Phenobarbital side effects, please contact your healthcare provider