Promethegan (Promethazine) - Rectal

Warning:

Promethegan has a black box warning, which is the strongest warning required by the Food and Drug Administration (FDA).

Promethegan (and all promethazine products) are not used in children under 2 years old, due to cases of respiratory depression that have occurred. Respiratory depression is when breathing slows or even stops. In some cases, this has caused death.

In children 2 years and older who are prescribed this medication, the lowest possible dose should be prescribed, and it should not be used in combination with other medications that can cause respiratory depression. Tell your child's healthcare provider if your child has any lung conditions such as asthma or sleep apnea, and tell the provider about all of the medications your child takes. If your child is taking this medicine and is wheezing, has difficulty breathing, or breathing slows or stops, get emergency medical help right away.

What Is Promethegan?

Promethegan (promethazine) is a rectal prescription drug used to treat various conditions such as allergic conditions, nausea and vomiting, and motion sickness. Promethegan, typically prescribed for people ages 2 to 65, contains the ingredient promethazine, which is in a drug class called phenothiazines/antihistamines.

Promethegan works on histamine H1 receptors in the body, which has an antiemetic (works against nausea and vomiting) and sedating effect.

Promethegan is available as a suppository that is inserted into the rectum. It is not to be put in the mouth.

Drug Facts

Generic Name: Promethazine

Brand Name(s): Promethegan, Phenergan

Drug Availability: Prescription

Therapeutic Classification: Gastrointestinal agent

Available Generically: Yes

Controlled Substance: No

Administration Route: Rectal

Active Ingredient: Promethazine

Dosage Form(s): Rectal suppository

What Is Promethegan Used For?

The Food and Drug Administration (FDA) approved Promethegan to:

  • Treat symptoms of allergic reactions, such as a runny nose and watery eyes
  • Treat allergic skin reactions/hives
  • Relax people before and after surgery
  • Prevent and control nausea and vomiting
  • Prevent and treat motion sickness

Promethegan does not treat symptoms of asthma, pneumonia, or other lower respiratory tract infections.

How to Use Promethegan

If you are prescribed Promethegan:

  • Read the prescription label and the information leaflet that comes with your prescription.
  • Consult your healthcare provider if you have any questions.
  • Use Promethegan exactly as directed by your provider.
  • Do not take Promethegan orally. It is for use only in the rectum.
  • Try to empty the bowels and bladder just before inserting a suppository.
  • Remove the wrapper before inserting the suppository.
  • Once unwrapped, insert the suppository quickly so it does not melt in your hands.
  • If possible, lie down for several minutes after inserting the suppository. This helps it to stay in place. The suppository will melt quickly once inserted.
  • Avoid using the bathroom right after you insert the suppository.
  • Contact your healthcare provider if your symptoms worsen or do not improve.
  • Tell your healthcare providers that you are using Promethegan rectal, as this medication can affect the results of certain medical tests.

Ask your healthcare provider if you have any questions or concerns about Promethegan.

Storage

Store Promethegan suppositories in the refrigerator, away from direct light. Do not freeze nor store in a bathroom. Keep away from children and pets.

Off-Label Uses

Sometimes, Promethegan is used off-label for indications that are not FDA-approved.
Healthcare providers may prescribe Promethegan to treat nausea and vomiting in people due to pregnancy, or morning sickness.

Because of the possibility of harm to the unborn baby, Promethegan is used in pregnant people only after other medications have not worked.

How Long Does Promethegan Take to Work?

Promethegan starts working within 15 minutes to an hour. The effects may last from two to eight hours.

What Are the Side Effects of Promethegan?

This is not a complete list of side effects, and others may occur. A medical professional can advise you on side effects. If you experience other effects, contact your healthcare professional. You may report side effects to the FDA at fda.gov/medwatch or 1-800-FDA-1088.

Like other medications, Promethegan can cause side effects. Tell your healthcare provider about any side effects you experience while taking this medication.

Common Side Effects

Common side effects of Promethegan include:

  • Drowsiness and dizziness
  • Sedation (slow reaction times)
  • Blurry vision
  • Confusion
  • Disorientation (feeling confused about the time, who you are, or where you are)
  • Extrapyramidal symptoms (involuntary muscle/facial movements)
  • Dry mouth
  • Sun sensitivity
  • Inflamed skin
  • Stuffy nose
  • Difficulty urinating

Severe Side Effects

Promethegan has a black box warning, which is the strongest warning required by the FDA.

Promethegan (and all promethazine products) are not used in children under 2 years old, due to cases of respiratory depression that have occurred. Respiratory depression is when breathing slows or even stops. In some cases, this has caused death.

In children 2 years and older who are prescribed this medication, the lowest possible dose should be prescribed, and it should not be used in combination with other medications that can cause respiratory depression.

Tell your child's healthcare provider if your child has any lung conditions such as asthma or sleep apnea, and tell the provider about all of the medications your child takes. If your child is taking this medicine and is wheezing, has difficulty breathing, or breathing slows or stops, get emergency medical help right away.

Call your healthcare provider right away if you have serious side effects. Call 911 if your symptoms feel life-threatening or if you think you’re having a medical emergency.

Serious side effects and their symptoms can include the following:

  • Hypersensitivity reaction or anaphylaxis: Symptoms can include rash, hives, swelling around the lips, tongue, and face, and difficulty breathing and require emergency medical attention. 
  • Apnea: Be alert to (or have your family/caregivers be alert to) loud snoring, choking/gasping while sleeping, and daytime drowsiness.
  • Respiratory depression: Be alert to weak and/or shallow breathing.
  • Seizures
  • Low white blood cell counts can interfere with the body's ability to fight infection. Be alert to weakness, fever, chills, and sore throat.
  • Low platelets, which can make you more likely to bruise or bleed easily; be alert to nosebleeds, bleeding gums, and easy bruising.
  • Hallucinations may cause you to see, hear, touch, taste, or smell something that is not there.
  • Extrapyramidal symptoms: Be alert to uncontrolled muscle movements in the face like chewing, lip smacking, frowning, tongue movement, and blinking/eye movement.
  • Jaundice is a yellowing of the skin or whites of the eyes.
  • Neuroleptic malignant syndrome: A rare, life-threatening reaction to medicine. Symptoms may include stiff muscles, high fever, sweating, confusion, fast or uneven heartbeats, tremors, and feeling like you might pass out.
  • Swelling under the skin
  • Bradycardia refers to fast or slow heartbeats.
  • Heat stroke: Symptoms may include high fever, sweating, and confusion.

Long-Term Side Effects

In many cases, Promethegan is used for nausea and vomiting when people cannot keep foods and drinks down and are throwing up frequently. This is because it is a suppository that is inserted rectally and won't be thrown up.

For its other uses, such as allergic conditions, there is an oral alternative (promethazine oral liquid) that can be used or other, newer antihistamines with fewer side effects. Because of these factors, Promethegan is generally used for a short period of time, and long-term side effects do not usually occur.

However, some general delayed or long-term side effects that can occur from Promethegan may include extrapyramidal side effects, anemia (low red blood cell levels), and thrombocytopenia (low platelet levels). People can discuss long-term side effects with their healthcare provider.

Report Side Effects

Promethegan may cause other side effects. Call your healthcare provider if you have any unusual problems while taking this medication. If you experience a serious side effect, you or your provider may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting Program online or by phone (800-332-1088).

Dosage: How Much Promethegan Should I Take?

Drug Content Provided and Reviewed by IBM Micromedex®

The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

  • For rectal dosage form (suppositories):
    • For allergy symptoms:
      • Adults and teenagers—12.5 milligrams (mg) before meals and at bedtime; or 25 mg at bedtime as needed.
      • Children 2 years of age and older—Your doctor will determine dose based on the weight and/or size of the child. The dose is usually 6.25 to 12.5 mg three times a day; or 25 mg at bedtime as needed.
      • Children younger than 2 years of age—Use and dose must be determined by your doctor .
    • For prevention of motion sickness:
      • Adults and teenagers—25 mg twice daily; this initial dose should be taken one-half to one hour before traveling. The dose may be repeated eight to twelve hours later if needed. On other days of travel, 25 mg may be taken on arising and again before the evening meal.
      • Children 2 years of age and older—Your doctor will determine dose based on the weight and/or size of the child. The dose is usually 12.5 to 25 mg one-half to one hour before traveling. The dose may be repeated eight to twelve hours later if needed.
      • Children younger than 2 years of age—Use and dose must be determined by your doctor .
    • For nausea and vomiting:
      • Adults and teenagers—25 mg for the first dose, then 12.5 to 25 mg every four to six hours if needed.
      • Children 2 years of age and older—Your doctor will determine dose based on the weight and/or size of the child. The dose is usually 0.5 mg per pound of body weight (1.1 mg per kg) or 12.5 to 25 mg every four to six hours as needed.
      • Children younger than 2 years of age—Use and dose must be determined by your doctor .
    • For sedation:
      • Adults and teenagers—25 to 50 mg.
      • Children 2 years of age and older—Your doctor will determine dose based on the weight and/or size of the child. The dose is usually 12.5 to 25 mg.
      • Children younger than 2 years of age—Use and dose must be determined by your doctor .
    • For control of pain or anxiety before or after surgery:
      • Adults and teenagers—50 mg the night before surgery; 25 to 50 mg after surgery.
      • Children 2 years of age and older—Your doctor will determine dose based on the weight and/or size of the child. The dose is usually 0.5 mg per pound of body weight (1.1 mg per kg) or 12.5 to 25 mg the night before surgery or after the surgery.
      • Children younger than 2 years of age—Use and dose must be determined by your doctor .

Modifications

Users should be aware of the following before beginning Promethegan:

Older adults: You may need to use caution when taking Promethegan if you are 65 years or older, especially if you have other medical conditions or take other medications. The prescribing information states that confusion and oversedation may occur in older adults, and this population should be started on low doses of Promethegan and monitored closely.

Often, a healthcare provider will recommend a different treatment for older adults to decrease the likelihood of severe side effects.

Children: Children under 2 years old should never use Promethegan. In some cases, healthcare providers may prescribe Promethegan suppositories to children 2 years and older with caution.

People with liver disease: People with liver disease will need to be closely monitored while taking Promethegan and may require a lower dosage.

People with kidney disease: People with kidney disease can generally take Promethegan without a dosage adjustment.

Pregnant people may be prescribed Promethegan if the healthcare provider determines that the benefits to the mother outweigh the risks to the unborn baby. Taking Promethegan within two weeks before the baby is delivered may affect blood clotting in the newborn.

Those nursing: While occasional, short-term use of Promethegan to treat nausea and vomiting may have little risk for the baby, repeated doses may cause excess sedation in the child. An alternative medication is generally preferred in those who are nursing.

Missed Dose

If you miss a dose of Promethegan, take it when you remember.

However, if it is almost time for the next dose, skip the missed dose. Do not use extra suppositories to try to make up for a missed dose.

Overdose: What Happens If I Take Too Much Promethegan?

An overdose of Promethegan may cause overactive reflexes, loss of coordination, severe drowsiness, weakness, fainting, dilated pupils, weak/shallow breathing, or seizures.

What Happens If I Overdose on Promethegan?

If you think you or someone else may have overdosed on Promethegan, call a healthcare provider or the Poison Control Center (800-222-1222). If someone collapses or isn't breathing after taking Promethegan, call 911 immediately.

Precautions

Drug Content Provided and Reviewed by IBM Micromedex®

It is very important that your doctor check your progress at regular visits to make sure this medicine is working properly. Blood tests may be needed to check for unwanted effects .

This medicine may affect blood sugar levels. If you notice a change in the results of your blood or urine sugar tests or if you have any questions, check with your doctor .

This medicine may cause some people to become dizzy, lightheaded, drowsy, or less alert than they are normally. Even if taken at bedtime, it may cause some people to feel drowsy or less alert on arising. Make sure you know how you react to this medicine before you drive, use machines, or do anything else that could be dangerous if you are not alert .

This medicine will add to the effects of alcohol and other CNS depressants (medicines that make you drowsy or less alert). Some examples of CNS depressants are antihistamines or medicine for hay fever, other allergies, or colds; sedatives, tranquilizers, antidepressants, or sleeping medicine; prescription pain medicine or narcotics; barbiturates; medicine for seizures; muscle relaxants; or anesthetics, including some dental anesthetics. Check with your medical doctor or dentist before taking any of the above while you are taking this medicine.

Check with your doctor right away if you have symptoms of pale or blue lips, fingernails, or skin; difficult or troubled breathing; irregular, fast, slow, or shallow breathing; or shortness of breath. These could be signs of a condition called respiratory depression .

Check with your doctor right away and stop taking your medicine (if directed by your doctor) if you have muscle stiffness, fever, difficult or fast breathing, seizures, fast heartbeat, increased sweating, loss of bladder control, unusually pale skin, or tiredness or weakness. These may be symptoms of a serious condition called neuroleptic malignant syndrome (NMS) .

Before you have any medical tests, tell the medical doctor in charge that you are taking this medicine. The results of some tests may be affected by this medicine .

This medicine may cause dryness of the mouth. For temporary relief, use sugarless candy or gum, melt bits of ice in your mouth, or use a saliva substitute. However, if your mouth continues to feel dry for more than 2 weeks, check with your medical doctor or dentist. Continuing dryness of the mouth may increase the chance of dental disease, including tooth decay, gum disease, and fungus infections .

This medicine may make your skin more sensitive to sunlight. Use a sunscreen when you are outdoors. Avoid sunlamps and tanning beds .

This medicine controls nausea and vomiting. For this reason, it may cover up some of the signs of overdose caused by other medicines or the symptoms of encephalopathy or Reye's syndrome. This will make it difficult for your doctor to diagnose these conditions. Make sure your doctor knows that you are using this medicine .

What Are Reasons I Shouldn't Take Promethegan?

Promethegan is not appropriate for everyone. Before taking Promethegan, tell your healthcare provider about all of your medical conditions, your medical history, and your family history.

You should not take this medication if you are allergic to promethazine or any phenothiazine (such as prochlorperazine) or any of the inactive ingredients in Promethegan.

Other people who should not take Promethegan include:

  • People who are in a coma
  • Children under 2 years old
  • People with respiratory depression
  • People with Reye's syndrome

Promethegan may be prescribed with caution in some people only if the healthcare provider determines it is safe. This includes:

  • Older adults
  • Children
  • People who take medications that cause central nervous system (CNS) depression (a slowing down of brain activity) like medicine for sleep or anxiety
  • People with liver problems
  • People with a seizure disorder or those at higher risk of having a seizure
  • People with angle-closure glaucoma (a serious eye condition that occurs when the fluid pressure inside the eye rises quickly)
  • People with asthma or chronic obstructive pulmonary disease (COPD)
  • People with heart disease, heart failure, or heart rhythm conditions
  • People who have recently had a heart attack
  • People with myelosuppression (a decreased production of blood cells)
  • People with intestinal or urinary blockages
  • People with prostate problems
  • People who live in an environment with high temperatures
  • People with electrolyte abnormalities (imbalance in the body's fluids)

What Other Medications May Interact With Promethegan?

Tell your healthcare provider about all of the medicines you take, including prescription and over-the-counter medicines, and vitamins or supplements.

While taking Promethegan, do not start any new medications without approval from your healthcare provider. Some drug interactions include:

CNS depressants: Promethegan causes CNS depression and should not be used with other drugs that cause CNS depression, such as:

If the combination of one of these medications with Promethegan cannot be avoided, a dosage adjustment will be required.

Anticholinergics: Promethegan has an anticholinergic effect, which means it can cause side effects like dry mouth, constipation, and difficulty urinating. Promethegan should not be used with other drugs that have anticholinergic effects, such as:

Monoamine oxidase inhibitors (MAOIs): Can cause an increased incidence of extrapyramidal side effects when combined with Promethegan. Examples of MAOIs include Nardil (phenelzine) and Parnate (tranylcypromine).

Solid forms of potassium (potassium supplements in pill form): Promethegan may delay potassium from moving through the body, causing levels of potassium that are too high.

This is not a full list of drug interactions. Other drug interactions may occur with Promethegan. Consult your healthcare provider for a complete list of drug interactions.

What Medications Are Similar?

Promethegan is a rectal suppository that treats various conditions such as nausea/vomiting, allergic conditions, and motion sickness.

Alternatives to Promethegan, then, would depend on why the medication is needed. Some alternatives include:

  • Compro (prochlorperazine) suppositories can be used rectally to treat severe nausea and vomiting. Prochlorperazine is also available as an oral medication to treat nausea and vomiting.
  • Zofran (ondansetron) and Zofran ODT (ondansetron orally disintegrating tablets) can be used to treat nausea and vomiting.
  • For allergic conditions, the ingredient in Promethegan, promethazine, is also available as an oral liquid that is taken by mouth. Newer antihistamines are usually preferred, though, because they cause fewer side effects. Examples include Claritin (loratadine), Xyzal (levocetirizine), or Zyrtec (cetirizine).
  • For motion sickness, Antivert (meclizine) is frequently prescribed.

This comprises a list of drugs also prescribed for certain conditions such as nausea/vomiting, allergic conditions, and motion sickness.

It is NOT a list of drugs recommended to take with Promethegan. Ask your healthcare provider if you have questions.

Frequently Asked Questions

  • What is Promethegan used for?

    Promethegan is a suppository that is inserted into the rectum and can be used to treat various conditions such as nausea/vomiting, allergic conditions, and motion sickness.

  • How does Promethegan work?

    Promethegan works on histamine H1 receptors in the body, which helps with conditions like nausea, vomiting, motion sickness, and allergies.

  • What drugs should not be taken with Promethegan?

    Before using Promethegan, tell your healthcare provider about all of the medications you take, including prescription and over-the-counter drugs, vitamins, and supplements.

    Promethegan can interact with certain drugs, such as those that cause a slowing of brain activity (like sleep medicines or anti-anxiety medications).

  • How long does it take for Promethegan to work?

    Promethegan starts to work as soon as 15 minutes to an hour.

  • What are the side effects of Promethegan?

    Common side effects may include drowsiness, dizziness, blurred vision, confusion, involuntary muscle movements (extrapyramidal symptoms), dry mouth, stuffy nose, and difficulty urinating.

    Consult your healthcare provider for a full list of side effects.

How Can I Stay Healthy While Taking Promethegan?

Although Promethegan is inserted into the rectum, it is absorbed into your body and can cause side effects, such as impaired thinking or reactions. Do not drive or operate machinery until you know how Promethegan affects you.

While taking Promethegan, stand up slowly to avoid dizziness. Avoid alcohol while taking Promethegan. Check with your healthcare provider before taking any other medications, even over-the-counter medications.

Promethegan can cause sun sensitivity and make you sunburn more easily. Avoid tanning beds and avoid the sunlight as much as you can. Wear protective clothing, sunglasses, and a hat and use sunscreen (and frequently reapply, especially if you are swimming or sweating) when you are outdoors.

Medical Disclaimer

Verywell Health's drug information is meant for educational purposes only and is not intended as a replacement for medical advice, diagnosis, or treatment from a healthcare professional. Consult your healthcare provider before taking any new medication(s). IBM Watson Micromedex provides some of the drug content, as indicated on the page.

8 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. DailyMed. Label: Promethegan: promethazine hydrochloride suppository.

  2. MedlinePlus. Promethazine.

  3. McParlin C, O'Donnell A, Robson SC, et al. Treatments for hyperemesis gravidarum and nausea and vomiting in pregnancy: a systematic reviewJAMA. 2016;316(13):1392-1401. doi:10.1001/jama.2016.14337

  4. Prescribers’ Digital Reference: Promethazine hydrochloride - drug summary.

  5. Epocrates. Promethazine rectal.

  6. Purohit TJ, Hanning SM, Wu Z. Advances in rectal drug delivery systemsPharm Dev Technol. 2018;23(10):942-952. doi:10.1080/10837450.2018.1484766

  7. National Library of Medicine. Promethazine. Drugs and Lactation Database.

  8. Addiction Center. Central nervous system depressants: what are central nervous system depressants?

By Karen Berger, PharmD
Karen Berger, PharmD, is a community pharmacist and medical writer/reviewer.