+ -Text Size



Trade/other name(s): Anergan, Phenergan

Why would this drug be used?

Promethazine is used to prevent or treat nausea, vomiting, and motion sickness. It is also used for several other conditions.

How does this drug work?

Promethazine is derived from a group of drugs called phenothiazines. It is used as a sedative, antihistamine, and mild anti-nausea medicine. It slows down the central nervous system (and is called a CNS depressant), but the exact mechanism is not known.

Before taking this medicine

Tell your doctor…

  • If you are allergic to anything, including medicines, dyes, additives, or foods.
  • If you have ever had seizures, have an abnormal EEG (brain wave study) or are taking anti-seizure medicines. This drug may raise your risk of seizures.
  • If you have prostate enlargement, a blockage in the bladder, or glaucoma. This drug can worsen the symptoms.
  • If you have an abnormal heart rhythm, heart block, heart failure, or any heart problem. Promethazine can lower the blood pressure and cause falling or fainting.
  • If you take tranquilizers (sedatives) such as diazepam (Valium) or drink alcohol. Promethazine may increase the sleepiness linked to these substances.
  • If you have any medical conditions such as kidney disease, liver disease (including hepatitis), stomach ulcers, blocked intestine, or diabetes. These conditions may require that your medicine dose, regimen, or timing be changed.
  • If you have asthma, emphysema, or sleep apnea (breathing problems). Promethazine can worsen these symptoms and make it harder to breathe.
  • If you will be exposed to extreme heat while taking promethazine. It can raise the risk of low blood pressure and other side effects.
  • If you are planning on having surgery in the near future. This drug can affect breathing when used with anesthetics.
  • If you are pregnant, trying to get pregnant, or if there is any chance of pregnancy. There may be an increased risk of harm to the fetus if a woman takes this drug during pregnancy. In addition, when a woman takes this drug during the last two weeks before delivery, the baby may have problems with blood clotting.
  • If you are breast-feeding. It is not known whether this drug passes into breast milk. If it does, it could harm the baby.

About any other prescription or over-the-counter medicines you are taking, including vitamins and herbs.

Interactions with other drugs

Substances that make you sleepy, such as alcohol, tranquilizers, opioid pain relievers, anesthetics, certain antidepressants, anti-anxiety drugs, and sleeping pills can make you much sleepier, worsen breathing, and cause serious harm when taken with promethazine. If you are on these medicines, your doctor may need to lower the dose you take.

Monoamine oxidase inhibitors such as phenelzine (Nardil), tranylcypromine (Parnate), isocarboxazid (Marplan), or selegiline (Emsam) may increase your risk of movement problems (extrapyramidal effects) if taken with promethazine. Antipsychotic medicines (taken for severe mental health problems) may increase your risk of other serious side effects.

Narcotics and local anesthetics can make seizures more likely while taking this drug.

Epinephrine may lower the blood pressure (rather than raise it) if it is given with haloperidol. The doctor can substitute another drug if epinephrine's effects are needed.

Check with your doctor, nurse, or pharmacist about whether any of the medicines, vitamins, herbs, and supplements you are taking can cause problems with promethazine.

Interactions with foods

No serious interactions with food are known at this time. Check with your doctor, nurse, or pharmacist about whether foods may be a problem.

Tell all the doctors, dentists, nurses, and pharmacists you visit that you are taking this drug.

How is this drug taken or given?

Promethazine can be given as a pill or liquid by mouth, as a rectal suppository, or as an injection in a vein over 5 minutes or in a muscle. Shake the liquid well before measuring the dose. The dose depends on the reason you are taking it. Take this drug exactly as directed by your doctor. If you do not understand the instructions, ask your doctor or nurse to explain them to you.

If you are taking the suppository, open the package and dip the tip of the suppository in water. If you are right-handed, lie down on your left side, bring your knees up near your chest, and insert the suppository in your rectum about an inch. Stay in this position for about 15 minutes, then get up and wash your hands well.

Keep the medicine in a tightly closed container away from heat and moisture and out of the reach of children and pets.


Promethazine may make you feel drowsy or dizzy. Do not drive or operate heavy machinery until you know the effect the drug will have. Talk to your doctor or nurse if you feel too drowsy or have dizziness that does not go away.

Promethazine may cause increased risk of confusion and drowsiness, especially in older people. It is important to protect against falls or injury. Be careful getting up, changing position, or walking. Start slowly and hold onto something or someone to hold you steady. Have another responsible adult with you until you know how the medicine will affect you and that you can take care of yourself.

Tell any doctor or dentist planning to do surgery on you that you are taking this drug. It can cause harm when used with anesthetic drugs.

Call your doctor or nurse right away if you have restlessness, muscle stiffness, severe anxiety, slow jerky movements, tiredness, weakness, fever, confusion, trouble walking, or yellow eyes or skin.

Promethazine may cause unplanned movements called extrapyramidal effects. These include restlessness, tremors, sticking out the tongue, muscle tightness, muscle spasms, and unplanned muscle movements. Let your doctor or nurse know right away if this happens. These side effects usually go away when the drug is stopped. The movements can also usually be stopped by other medicines such as diphenhydramine (Benadryl). In some cases, your doctor may need to stop the promethazine.

Promethazine may raise your risk of seizures if you have had them before.

This drug can cause a rare problem called neuroleptic malignant syndrome, with symptoms like fever, tight muscles, tremors, sweating, constipation, and confusion. This syndrome can become life-threatening if not treated right away. If you have symptoms like these, call your doctor without delay.

Promethazine may cause certain pregnancy tests to give wrong results.

Possible side effects

You will probably not have most of the following side effects, but if you have any talk to your doctor or nurse. They can help you understand the side effects and cope with them.


  • drowsiness or sleepiness
  • dry mouth
  • constipation

Less common

  • confusion (especially in older patients)*
  • sedation (calmness, tranquility)
  • restlessness
  • involuntary muscle movements or spasms (extrapyramidal effects)*
  • tremors*
  • blurred vision
  • low blood pressure when first sitting or standing up, with dizziness, falling, or fainting*


  • nausea
  • vomiting
  • trouble passing urine
  • higher blood sugar levels
  • damage to liver (yellowing of the skin and the whites of the eyes)
  • increased sensitivity to sunlight with higher risk of sunburn
  • severe allergic reaction with itching, hives (skin welts), dizziness, trouble breathing or swallowing, swelling of the mouth, tongue, or face
  • low white blood count with increased risk of infection
  • neck spasms (cramps) and tightness in the throat, trouble swallowing
  • hallucinations (seeing or hearing things that aren't there)
  • seizures
  • paradoxical (opposite) reaction in which the person gets "hyper" and excited

*See the "Precautions" section for more detailed information.

There are other side effects not listed above that can also occur in some patients. Tell your doctor or nurse if you develop these or any other problems.

FDA approval

Yes – first approved before 1984 (FDA cannot verify dates of drugs approved before 1984.)

Disclaimer: This information does not cover all possible uses, actions, precautions, side effects, or interactions. It is not intended as medical advice, and should not be relied upon as a substitute for talking with your doctor, who is familiar with your medical needs.

Last Medical Review: 10/14/2009
Last Revised: 10/14/2009