Promethazine (Rectal)

Promethazine suppositories are administered rectally to treat and prevent motion sickness, nausea and vomiting, and allergic rhinitis.


Promethazine is a type of phenothiazine which is used to treat a variety of conditions by blocking certain chemicals in the brain. It is often prescribed to manage symptoms of allergic rhinitis and conjunctivitis, such as itchy nose and eyes, runny nose, sneezing, hives and skin rash. It can also be used to prevent motion sickness and to reduce nausea and vomiting after surgery. The drug has sedative effects and is also sometimes use to induce sleep or relax a patient before and after surgery, or at other times in which a patient may feel anxious.

Although promethazine can help to relieve allergic rhinitis, it should not be used to treat lower respiratory tract conditions such as asthma or pneumonia. This is because the drug can sometimes close up the air passages of the lungs and make breathing difficult, an effect which is more likely in patients with lower respiratory tract problems.

Promethazine is only available with a doctor's prescription. For the rectal drug route, promethazine is administered in suppository form and is available under the following brand names:

  • Phenadoz
  • Promethegan

This drug is also available in tablet form to be taken orally, but the rectal drug route is often more tolerable to patients with nausea or vomiting because it will not cause gastric irritation.

Conditions Treated?

  • Allergic rhinitis
  • Allergic conjunctivitis
  • Motion sickness
  • Nausea/vomiting

Type Of Medicine?

  • Phenothiazine

Side Effects

Promethazine can cause unwanted side effects as well as its intended effects. Some side effects are serious and should be reported to a doctor urgently, while others are minor and do not require medical attention unless they become prolonged.

The following side effects are rare, but should be reported to a doctor immediately if they occur:

  • Seizures (convulsions)
  • Severe muscle stiffness
  • Loss of bladder control
  • Unusual weakness or tiredness
  • Difficulty breathing
  • Unusually fast breathing
  • Fast or irregular heartbeat
  • Abnormally high or low blood pressure
  • High fever
  • Increased sweating
  • Pale skin

The following are potential side effects of promethazine but the frequency at which they occur is not known. They should be reported to a doctor immediately.

  • Pain in back or side
  • Chest pain, tightness or discomfort
  • Cough or hoarseness
  • Sore throat
  • Swollen glands
  • Troubled or difficult breathing
  • Wheezing
  • Fast, irregular or pounding heartbeat or pulse
  • Fast, irregular or shallow breathing
  • Noisy breathing
  • Stopped breathing
  • Stomach or abdomen pain
  • Loss of appetite
  • Nausea
  • Vomiting blood
  • Black or tarry stools
  • Clay-colored stools
  • Blood in stools or urine
  • Dark urine
  • Bleeding gums
  • Bloody nose
  • Stuffy nose
  • Fixed eye position
  • Blurred vision
  • Double vision
  • High fever (with or without chills)
  • Chills
  • Headache
  • Confusion
  • Negativism
  • Holding false beliefs or delusions
  • Hallucinations (hearing, seeing or feeling things that aren't there)
  • Reduced awareness or responsiveness
  • Hyperexcitability
  • Unusual restlessness, nervousness or excitement
  • Nightmares
  • Lightheadedness, dizziness or fainting
  • Mimicry of speech or movements
  • Peculiar movements, postures, mannerisms
  • Sticking out tongue
  • Grimacing
  • Tremors
  • Uncontrollable twisted movements of neck
  • Mutism
  • Unusually heavy menstrual periods
  • Itching
  • Skin rash
  • Hive-like swellings on the face, tongue, throat, hands legs, feet or genitals
  • Pinpoint red spots on skin
  • Sores, ulcers or white spots in mouth or on lips
  • Blue or pale lips, fingernails or skin
  • Abnormal bruising or bleeding
  • Yellow eyes or skin


An overdose of promethazine can be incredibly dangerous. If you think you have taken more promethazine than you should have done, contact your doctor immediately or call your local poison control center. If you notice any of the following symptoms of overdose, call 911 immediately.

  • Dry mouth
  • Excessive muscle tone
  • Muscle tightness or tension
  • Overactive reflexes
  • Shakiness or unsteady walk
  • Trembling
  • Poor muscle control or coordination
  • Feeling of warmth
  • Lack of appetite
  • Difficulty concentrating
  • Discouragement
  • Sadness or emptiness
  • Loss of pleasure or interest
  • Irritability
  • Nightmares
  • Pupils unresponsive to light or not moving
  • Flushing of the face, neck, arms or upper chest
  • Unusual paleness
  • Difficulty sleeping
  • Unconsciousness

The following side effects associated with promethazine are minor and don't usually require medical attention. In many instances they will dissipate once your body adjusts to the medicine. However, if they persist or become very severe, consult your doctor.

  • Blistering, crusting, irritation, itching or reddening skin
  • Dry, cracked or scaly skin
  • Redness or discoloration of skin
  • Increased skin sensitivity to sunlight
  • Sunburn
  • Swelling
  • Ringing or buzzing sound in ears
  • Mild hearing loss
  • Lack of coordination
  • Reduced energy or strength
  • Muscle weakness or discomfort
  • Drowsiness
  • Relaxed, calm state
  • Excited state
  • False or unusual sense of well-being
  • Mild hives or welts
  • Vomiting

If you notice any other side effects not listed here, consult a doctor as soon as possible. You could also report side effects to the FDA.


For treatment of allergy symptoms:

Adults and teenagers “ either:

  • 12.5 mg before meals and at bedtime, or
  • 25 mg at bedtime

Children aged 2 and over “ either:

  • Between 6.25 mg and 12.5 mg three times each day, or
  • 25 mg at bedtime
  • Dose determined by weight and size of child

Children under 2 “ use and dose determined by doctor

For prevention of motion sickness:

Adults and teenagers:

  • 25 mg twice daily
  • Initial dose taken between 30 and 60 minutes before travel
  • Second dose taken 8 to 12 hours after first if necessary
  • For long trips, take first dose in morning and second before evening meal on each day of travel

Children aged 2 and over:

  • Between 12.5 mg and 25 mg
  • Take between 30 and 60 minutes before travel
  • Repeat dose if needed between 8 and 12 hours later
  • Dose determined by weight and size of child
  • Children under 2 “ use and dose determined by doctor

For treatment of nausea and vomiting

Adults and teenagers

  • 25 mg for initial dose
  • 12.5 mg to 25 mg taken four to six hours after initial dose as needed

Children aged 2 and over:

  • Between 12.5 mg and 25 mg taken every four to six hours as needed
  • Dose determined by weight and size of child
  • Typically 0.5 mg per pound of body weight
  • Children under 2 “ use and dose determined by doctor

For sedation:

  • Adults and teenagers “ between 25 and 50 mg

Children aged 2 and over:

  • Between 12.5 and 25 mg
  • Dose determined by weight and size of child
  • Children under 2 “ use and dose determined by doctor

For control of anxiety and pain before or after surgery:

Adults and teenagers:

  • 50 mg the night before surgery
  • Between 25 mg and 50 mg after surgery

Children aged 2 and over:

  • Between 12.5 mg and 25 mg the night before surgery and after surgery
  • Dose determined by weight and size of child
  • Typically 0.5 mg per pound of body weight
  • Children under 2 “ use and dose determined by doctor

How to use promethazine suppositories

Suppositories are provided in foil wrappers. You should be able to feel how soft the suppository is while it is still wrapped; if it feels too soft to easily insert, you could place it in the fridge for 30 minutes or run it under cold water for a few minutes to firm it up. Once ready to use, wash your hands, remove the foil wrapper and run the suppository under water to moisten it.

Lie on your left side and bring your right knee to your chest (or lie on the right and raise the left knee if left-handed). Use your finger to push the suppository into the rectum. It should be around an inch inside the rectum for adults (2.5cm) or half an inch (1.25cm) for young children. Hold the suppository in place for a few moments. Remain lying down for around 15 minutes before getting up and wash your hands straight away.

Never take rectal suppositories by mouth as doing so could cause serious side effects.

Missed doses

If you miss a dose of promethazine, take it as soon as you remember. However, if it is almost time for your next dose, skip the missed dose and follow your normal dosing schedule. Do not double doses of this medicine or insert more than one suppository at one time.


There are many drug interactions associated with promethazine. Make sure your doctor knows about all the medicines you take, including those which are prescribed, those purchased over the counter, and those which are herbal medicines or supplements. It may be helpful to write down a list of all medicines you take so that any doctor or pharmacist you see can avoid recommending drugs which could cause harmful interactions.

It is particularly important to tell your doctor if you take any of the following types of medication:

  • Anti-anxiety medicines
  • Antidepressants
  • Other medicines for mental illness
  • MAO inhibitors
  • Antihistamines
  • Barbiturates
  • Cancer chemotherapy
  • Epinephrine (EpiPen)
  • Irritable bowel disease medicines
  • Parkinson's disease medicines
  • Anti-seizure medicines
  • Muscle relaxants
  • Narcotics and pain medicines
  • Sedatives and sleeping pills or tranquilizers
  • Medicines for urinary problems

The following medicines are not recommended for use with promethazine under any circumstances. If you take any of these drugs, your doctor may change some of them or avoid prescribing promethazine:

  • Amifampridine
  • Amisulpride
  • Bepridil (Vascor)
  • Bromopride
  • Cisapride (Propulsid)
  • Dronedarone (Multaq)
  • Mesoridazine (Serentil)
  • Metoclopramide (Metozolv ODT, Reglan)
  • Pimozide (Orap)
  • Piperaquine
  • Saquinavir (Invirase, Fortovase)
  • Sodium Oxybate (Xyrem)
  • Sparfloxacin
  • Terfenadine (Seldane)
  • Thioridazine (Mellaril, Mellaril-S)
  • Ziprasidone (Geodon)

The following medicines may increase the risk of side effects when taken at the same time as promethazine:

  • Belladonna (Belladonna Tincture, Belladonna Leaf)
  • Betel Nut
  • Evening Primrose (Primrose Oil, Evening Primrose Oil)
  • Meperidine (Demerol HCl)
  • Midodrine (ProAmatine, Orvaten)
  • Phenylalanine

Where other interactions occur, which are not recommended but may be necessary if both drugs are essential, your doctor may adjust the dosages of some medicines you take or give additional instructions as to the time at which you take them. Always follow your doctor's instructions carefully as failure to do so could cause serious side effects or complications.

Medical interactions

Promethazine should never be used in patients with the following conditions due to a heightened risk of life-threatening side effects:

  • Brain injury or brain disease
  • Breathing or lung problems (such as asthma, COPD, bronchitis, etc)
  • Comatose state (unconsciousness)
  • Reye's syndrome
  • Sleep apnea or a history of

Some medical conditions can be worsened by promethazine. If you have any of the following conditions, make sure your doctor knows about them:

  • Heart or blood vessel disease
  • Bone marrow disease
  • Intestinal tract obstruction
  • Stomach ulcer
  • Liver disease
  • Jaundice
  • Neuroleptic malignant syndrome or a history of
  • Urinary tract blockage or difficult urination
  • Enlarged prostate
  • Glaucoma

In patients with seizure disorders (such as epilepsy), promethazine could increase the risk of seizures. The risk of this is higher in those who are also using anesthetic or narcotic medicines. Make sure your doctor knows about all the medicines you take if you have a seizure disorder.


Risk of respiratory depression

Promethazine can cause respiratory depression, in which breathing becomes very slow. In some cases, breathing may stop altogether which could lead to death. The risk of this is particularly high in children under the age of two.

To minimize this risk, patients should avoid taking other medicines which are also known to cause respiratory depression. This includes many antidepressants, anti-anxiety medicines, sedatives, sleeping aids, narcotic pain killers, and some antihistamines and cold and flu medicines. Make sure your doctor knows about all prescription and over-the-counter (OTC) drugs you take.

Patients with preexisting breathing or lung problems may be at a higher risk of respiratory depression when taking promethazine. The drug may not be administered if you have, or have a history of:

  • Asthma
  • Sleep apnea
  • Bronchitis
  • Emphysema
  • Chronic obstructive pulmonary disease (COPD)

Elderly patients

Promethazine can be just as effective a treatment for elderly patients as it is for younger adults, but lower initial doses may be administered. This is because elderly patients may be more sensitive to confusion, severe drowsiness and other side effects associated with the drug. Furthermore, elderly patients are more likely to have liver problems, kidney disease, or heart or blood vessel disease as a result of their age which may be worsened by this drug. These patients are usually monitored more closely, and their dose increased as necessary only when monitoring proves that it is safe to do so.

Pediatric patients

Promethazine is not suitable for use in children under the age of two. This is due to the risk of fatal respiratory depression which is heightened in very young children and babies. In children over two, promethazine may be administered but with great caution and with dosages determined by the size and weight of the child. In teenagers, the drug is safer but doses often begin at the lower end and are increased as necessary.

Increased sensitivity to sunlight

Promethazine can cause the skin to become more sensitive to sunlight, which can increase the risk of painful sunburn. Patients should avoid prolonged sun exposure while taking this medicine. Take care to apply sunscreen liberally and regularly to all areas of exposed skin should you have to go out in the sun.


This medicine could make you drowsy or dizzy. Avoid driving or operating machinery when you first start treatment with promethazine until you know how it affects you. Only drive or operate machinery if you feel confident that the drug doesn't cause significant drowsiness.

Pregnancy and breastfeeding

This drug is a pregnancy category C medicine, which means it should only be used in pregnant women if benefits of the drug far outweigh potential risks to the fetus.

Animal studies have demonstrated a risk to the fetus, and there have not been enough controlled studies in humans to determine the risks. There is some evidence that when promethazine is taken within the last two weeks of pregnancy that the newborn baby demonstrates irritability, excitement and inhibited platelet aggregation, which means that blood cannot clot. There is also evidence that high doses administered in the later stages of pregnancy could cause neurological problems in the newborn baby.

Promethazine is excreted in human breast milk and nursing infants could experience sedation, irritability, and excitement. The drug is therefore not recommended for use while breastfeeding. If your doctor is considering prescribing this medicine while you are breastfeeding, you will have to decide whether to avoid the drug or discontinue breastfeeding.


Your doctor should know about all allergies you suffer from, including pollen, food, chemical, animal, dye and preservative allergies. This is to avoid you experiencing a harmful reaction to any of the ingredients in promethazine suppositories. If you have had a reaction to promethazine in the past, you should not use the medicine again.

If you notice any symptoms of allergic reaction, listed below, contact your doctor immediately:

  • Itching, rash or hives
  • Blistering or peeling skin
  • Swollen eyelids, face, lips, tongue or throat
  • Chest tightness or shortness of breath
  • Wheeze or cough

Avoid alcohol

Alcohol can increase the risk of respiratory depression when consumed during promethazine treatment. Furthermore, alcohol can worsen drowsiness or dizziness associated with this drug. You should therefore avoid alcohol while using promethazine suppositories.


Store promethazine suppositories in the packaging they are provided in and in a refrigerator. You should keep the suppositories from freezing and keep them away from direct light, moisture or heat. The bathroom is therefore not the best place to keep this medicine.

Keep promethazine suppositories well away from children and pets by storing them up and away from the ground. This medicine can be extremely harmful if consumed by children.

If you have outdated or unused promethazine suppositories, dispose of them appropriately. Your local recycling center or your healthcare provider may have a medicine take-back program that you could use to ensure the suppositories are correctly disposed of and don't come into contact with other people, children or animals.


Promethazine is a phenothiazine, which works to block certain chemicals in the brain in order to alleviate a variety of symptoms. It is commonly used to treat and prevent motion sickness, to relieve the symptoms of allergic rhinitis and sometimes to relax or induce sleep in patients before surgery. It may also be used after surgery to relieve nausea and vomiting which may be caused by anesthesia. The rectal drug route of promethazine is often helpful for patients who experience nausea and vomiting because it does not cause gastral irritation as the oral route can.

The biggest risk associated with promethazine is respiratory depression, which can cause breathing to slow or even stop in severe cases. The risk of fatal respiratory depression is particularly high in children, and the drug is used with great caution in pediatric patients. It is not recommended for use in those under the age of two, but small doses, determined by the size and weight of the patient, may be administered to children aged two years and over. Teenagers are often tolerable to higher doses. In elderly patients, lower doses may also be administered initially due to the likelihood of age-related liver or kidney problems, or heart or blood vessel disease.

Due to the risk of respiratory depression, promethazine is not suitable for patients with preexisting lung or breathing problems, such as asthma, COPD and sleep apnea. It should also be avoided in patients with Reye's syndrome, brain injury or brain disease, and in those who are in a comatose state. The drug should be used with caution in patients with heart or blood vessel disease, liver disease and enlarged prostate.

Promethazine can cause drowsiness and dizziness. Patients should avoid alcohol while taking this medicine as it could worsen these effects. Driving and operation of machinery should be avoided until patients know how the drug affects them.

For the prevention of motion sickness, one suppository should be inserted around an hour before travel and every eight to twelve hours thereafter when necessary. For nausea, patients should take one dose every four to six hours as needed. If the drug is to be used to manage anxiety and pain associated with surgery, one dose should be administered the night before surgery and another after surgery. Doses vary depending on the age of the patient and in children the dose is usually determined based on their weight and size.

Promethazine suppositories should be refrigerated to ensure they are firm enough for easy insertion. Patients should remove the suppository wrapping, run it under water to moisten it, then lay on their side with one knee raised to insert the suppository into the rectum comfortably. It is best to remain lying down for around 15 minutes after insertion. Hands should be washed thoroughly both before and after insertion of suppositories.