Generic name: Promethazine hydrochloride.

Phenergan is an antihistamine. Antihistamines block the efffects of histamine, a body chemical that causes swelling and itching. 

Quick Facts About Phenergan


Used to relieve nasal stuffiness and inflammation, and red, inflamed eyes caused by hay fever and other allergies. Also used to treat itching, swelling, and redness from hives and other rashes, allergic reactions to blood transfusions. Prescribed with other medications to treat anaphylactic shock (severe allergic reaction). Also prescribed as a sedative for children and adults, to prevent and control nausea and vomiting before and after surgery, to prevent and treat motion sickness, and for pain after surgery.

Phenergan Dosage

Take exactly as prescribed.

  • Usual adult dose: for allergy — oral dose of 25 milligrams taken before bedtime, or 12.5 milligrams before meals and before bed. For motion sickness — 25 milligrams taken 2 times per day. First dose should be taken to 1 hour before travel, and second dose 8 to 12 hours later. Then 25 milligrams in the morning and before evening meal. For nausea and vomiting — 25 milligrams orally, or if cannot be tolerated, rectal suppository. Doctor may advise 12.5 to 25 milligrams every 4 to 6 hours if necessary. For insomnia — 25 to 50 milligrams at bedtime.
  • Usual child dose: for allergy-a single 25 milligram dose at bedtime or 6.25 to 2.5 milligrams 3 times per day. For motion sickness — 12.5 to 25 milligrams taken 2 times per day in tablet, syrup, or rectal suppository form. For nausea and vomiting — 0.5 milligram per pound of body weight; age of child and severity of condition are taken into consideration. For insomnia — 12.5 to 25 milligrams by tablet or rectal suppository at bedtime.
  • Missed dose: if taking on a regular schedule — 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.

Phenergan Side Effects

Overdose symptoms:

difficulty breathing, dry mouth, fixed or dilated pupils, flushing, loss of consciousness, slowdown in brain activity, slowed heartbeat, stomach and intestinal problems, very low blood pressure. If you suspect an overdose, immediately seek medical attention.

More common side effects: blurred vision, dizziness, dry mouth, increased or decreased blood pressure nausea, rash, sedation, sleepiness, vomiting.

Rare Phenergan side effects: abnormal eye movements, blood disorders, confusion, disorientation, protruding tongue, sensitivity to light, stiff neck.


Inform your doctor before combining Phenergan with:

Inform your doctor before combining Phenergan with: certain antidepressants, including Elavil and Tofranil, narcotic pain relievers such as Demerol and Dilaudid, sedatives such as Halcion and Seconal, tranquilizers such as Xanax and Valium.

Do not drink alcohol while taking Phenergan.

Special Cautions

If pregnant or planning to become pregnant, inform your doctor immediately. May affect pregnancy test results. May appear in breast milk; could affect a nursing infant

No special precautions apply to seniors.

Follow doctor’s instructions carefully for children 2 years and older. May cause drowsiness; supervise children carefully when bike-riding, roller-skating, or participating in other potentially hazardous activities.

  • May cause drowsiness and impair your ability to drive a car or operate machinery. Do not take part in any activity that requires alertness. Doctor may reduce other medications you are currently taking if they also cause drowsiness.
  • Should not use if sensitive to or allergic to this or similar medications such as Thorazine, Mellaril, Stelazine, or Prolixin.
  • Phenergan may prompt seizures in people who already experience them.
  • Should not take if you have sleep apnea (periods of sleep when breathing stops).
  • Use with caution if you have: heart disease, high blood pressure or circulatory problems, liver problems, narrow-angle glaucoma, peptic ulcer or other abdominal obstructions, or urinary bladder obstruction due to enlarged prostate.
  • May raise blood sugar.
  • You may experience jaundice (yellow eyes and skin) during Phenergan therapy.
  • Inform your doctor if you experience any uncontrolled movements or unusual sensitivity to sunlight

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 Phenergan side effects, please contact your healthcare provider