Promethazine, Oral Tablet

Medically reviewed by Creighton University, Center for Drug Information and Evidence-Based Practice on November 30, 2015Written by University of Illinois-Chicago, Drug Information Group

Important warnings

FDA warning: Breathing problems in young children

  • This drug has a black box warning. This is the most serious warning from the Food and Drug Administration (FDA). A black box warning alerts doctors and patients about drug effects that may be dangerous.
  • Promethazine can cause breathing problems in young children. It should not be used in children younger than 2 years. In children this age, this drug may cause slowed breathing that may result in death. Caution should be used when giving this drug to children older than 2 years. Also, this drug should not be used in children who are taking other drugs that may cause slowed breathing.
  • Extreme drowsiness warning: This drug may cause extreme drowsiness. Don’t drive a car or use machinery until you know how this drug affects you.
  • Neuroleptic malignant syndrome warning: The use of this drug is linked with neuroleptic malignant syndrome. This condition can be fatal. Symptoms can include fever, rigid muscles, mental changes, changes in pulse or blood pressure, fast heartbeat, increased sweating, or irregular heart rhythm.

What is promethazine?

Promethazine is a prescription drug. It’s available as an oral solution, a rectal suppository, and an oral tablet.

The oral tablet is only available as a generic drug. Generic drugs usually cost less than brand-name versions.

Why it's used

Promethazine is used for several reasons, including treating allergies, motion sickness, nausea and vomiting, anxiety before surgery, and pain after surgery. It’s also used as a sleep aid, including before and after surgery.

This drug may be used as part of a combination therapy. This means you may need to take it with other medications.

How it works

This drug belongs to two classes of drugs called antihistamines and antiemetics. A class of drugs is a group of medications that work in a similar way. These drugs are often used to treat similar conditions.

Promethazine works by preventing the release of a substance called histamine from certain cells in your body. Histamine is normally released when you’re exposed to things you’re allergic to, such as pollen, dander, mold, or chemicals.

By preventing the release of histamine, this drug causes sleepiness and helps with pain control. This is because histamine helps regulate wakefulness and helps to keep you alert and your senses heightened.

This drug also works to reduce stimulation of the part of your brain that sends signals to make you vomit.

Promethazine side effects

This drug can cause extreme drowsiness. It can also cause other side effects.

More common side effects

The more common side effects that can occur with promethazine oral tablet include:

  • drowsiness
  • changes in blood pressure
  • allergic skin reactions
  • reduced platelet counts
  • reduced white blood cell production
  • breathing problems
  • increased excitability
  • abnormal movements

If these effects are mild, they may go away within a few days or a couple of weeks. If they’re more severe or don’t go away, talk to your doctor or pharmacist.

Serious side effects

Call your doctor 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:

  • Extrapyramidal symptoms (uncontrollable movements). Symptoms can include:
    • uncontrollable upward staring, and eye and lid twitching
    • uncontrollable neck muscle contractions causing your head to twist or turn to one side
    • sticking your tongue out uncontrollably
  • Seizures
  • Hallucinations (seeing things that aren’t there)
  • Abnormal heart rhythm. Symptoms can include:
    • palpitations
    • dizziness
    • fainting
    • shortness of breath
    • chest pain
    • light headedness
  • Decreased platelet and white blood cell production. Symptoms can include:
    • bruising or abnormal bleeding. This includes bleeding from minor cuts, nose or mouth bleeding, and pinpoint red spots on your skin. It also includes abnormally heavy menstrual flow, blood in your urine, or black tarry stools.
    • fevers or infections
  • Severe breathing problems
  • Angioedema (buildup of fluid deep in your skin or underneath your skin). Symptoms can include:
    • swelling usually around your eyes and lips and sometimes your throat, hands, and feet
    • swelling on the surface of your skin (welts)
    • painful and itchy welts (hives)
  • Neuroleptic malignant syndrome (a reaction to antipsychotic drugs that is sometimes fatal). Symptoms can include:
    • fever
    • muscle rigidity
    • mental changes
    • changes in pulse or blood pressure
    • fast heart rate
    • increased sweating
    • irregular heart rhythm
  • Jaundice. Symptoms can include:
    • yellow skin
    • yellowing of the whites of your eyes
    • dark or brown-colored urine
    • yellowing of the inside of your mouth
    • pale or clay-colored stools

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this information includes all possible side effects. This information is not a substitute for medical advice. Always discuss possible side effects with a healthcare provider who knows your medical history.

Promethazine may interact with other medications

Promethazine oral tablet can interact with other medications, vitamins, or herbs you may be taking. An interaction is when a substance changes the way a drug works. This can be harmful or prevent the drug from working well.

To help avoid interactions, your doctor should manage all of your medications carefully. Be sure to tell your doctor about all medications, vitamins, or herbs you’re taking. To find out how this drug might interact with something else you’re taking, talk to your doctor or pharmacist.

Examples of drugs that can cause interactions with promethazine are listed below.

Allergy drugs

When you take certain allergy drugs with promethazine, you may have increased side effects. These can include dry mouth, constipation, trouble emptying your bladder, blurred vision, and drowsiness. Examples of these drugs include:

  • brompheniramine
  • carbinoxamine
  • chlorpheniramine
  • clemastine
  • cyproheptadine
  • diphenhydramine
  • hydroxyzine

Antidepressant drugs

If you take certain antidepressant drugs called monoamine oxidase inhibitors (MAOIs) with promethazine, you raise your risk of extrapyramidal symptoms. These symptoms include uncontrollable upward staring, eye and lid twitching, uncontrollable neck muscle contractions (causing your head to twist or turn to one side), and sticking out your tongue uncontrollably. Examples of these drugs include:

  • isocarboxazid
  • phenelzine
  • tranylcypromine

When you take drugs called tricyclic antidepressants with promethazine, you may have drowsiness that is more extreme and lasts longer. Examples of these drugs include:

  • amitriptyline
  • amoxapine
  • clomipramine
  • desipramine
  • doxepin
  • imipramine
  • nortriptyline
  • protriptyline
  • trimipramine

Anxiety drugs

When you take certain anxiety drugs with promethazine, you may have drowsiness that is more extreme and lasts longer. Examples of these drugs include:

  • alprazolam
  • chlordiazepoxide
  • clonazepam
  • clorazepate
  • diazepam
  • hydroxyzine
  • lorazepam
  • oxazepam

Bladder control drugs

When you take certain bladder control drugs with promethazine, certain side effects may increase and last longer. These side effects include dry mouth, constipation, trouble emptying your bladder, blurred vision, and drowsiness. Examples of these drugs include:

  • darifenacin
  • flavoxate
  • oxybutynin
  • solifenacin
  • tolterodine
  • trospium

Muscle relaxants

When you take certain muscle relaxants with promethazine, you may have drowsiness that is more extreme and lasts longer. Examples of these drugs include:

  • baclofen
  • carisoprodol
  • chlorzoxazone
  • cyclobenzaprine
  • dantrolene
  • metaxalone
  • methocarbamol
  • orphenadrine
  • tizanidine

Nausea and motion sickness drugs

When you take certain nausea and motion sickness drugs with promethazine, certain side effects may increase and last longer. These side effects include dry mouth, constipation, trouble emptying your bladder, blurred vision, and drowsiness. Examples of these drugs include:

  • dimenhydrinate
  • meclizine
  • scopalamine

Pain drugs

When you take certain pain drugs with promethazine, you may have drowsiness that is more extreme and lasts longer. Examples of these drugs include:

  • codeine
  • fentanyl
  • hydrocodone
  • hydromorphone
  • levorphanol
  • meperidine
  • methadone
  • morphine
  • oxycodone
  • oxymorphone
  • tramadol

Parkinson’s disease drugs

When you take certain Parkinson’s disease drugs with promethazine, some side effects may increase and last longer. These side effects include dry mouth, constipation, trouble emptying your bladder, blurred vision, and drowsiness. Examples of these drugs include:

  • benztropine
  • trihexyphenidyl
  • amantadine

Seizure drug

Taking phenobarbital with promethazine may lower levels of promethazine in your body. Promethazine may not work well at this lowered level.

Sleep medications

When you take certain sleep aids with promethazine, you may have drowsiness that is more extreme and lasts longer. Examples of these drugs include:

  • chloral hydrate
  • estazolam
  • eszopiclone
  • flurazepam
  • temazepam
  • triazolam
  • zaleplon
  • zolpidem

Stomach and gastrointestinal drugs

When you take certain stomach and gastrointestinal drugs with promethazine, certain side effects may increase and last longer. These side effects include dry mouth, constipation, trouble emptying your bladder, blurred vision, and drowsiness. Examples of these drugs include:

  • belladonna alkaloids/phenobarbital
  • chlordiazepoxide/clinidium
  • dicyclomine
  • glycopyrrolate
  • hyoscyamine
  • methscopolamine
  • scopolamine

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs interact differently in each person, we cannot guarantee that this information includes all possible interactions. This information is not a substitute for medical advice. Always speak with your healthcare provider about possible interactions with all prescription drugs, vitamins, herbs and supplements, and over-the-counter drugs that you are taking.

Promethazine warnings

This drug comes with several warnings.

Allergy warning

This drug can cause a severe allergic reaction. Symptoms can include:

  • trouble breathing
  • swelling of your throat or tongue

Call 911 or go to the nearest emergency room if you develop these symptoms.

Don’t take this drug again if you’ve ever had an allergic reaction to it. Taking it again could be fatal (cause death).

Alcohol interaction

Drinking alcohol can make drowsiness from promethazine more extreme and last longer. To avoid this, don’t drink alcohol while you are taking this drug.

Warnings for people with certain health conditions

For people with angle-closure glaucoma: Angle-closure glaucoma leads to increased pressure in your eyes. If you have a history of angle-closure glaucoma, taking this drug may cause a sudden and severe increase in eye pressure. This is an emergency and may result in irreversible vision loss. Talk to your doctor before using this drug if you have this condition.

For people with enlarged prostate: If you have trouble urinating due to an enlarged prostate gland, taking this drug may make it even more difficult for you to urinate.

For people with certain stomach problems: If you have a history of digestive tract blockage, taking this drug may make blockage worse. This is because this drug slows down movement through your digestive tract.

For people with certain bladder problems: If you have a blockage in your bladder, taking this drug may make it more difficult for you to urinate. This is because it narrows the tubes through which your urine flows.

For people with bone marrow disease: This drug decreases your levels of platelets and white blood cells. You should not take it if you have bone marrow disease or you take other drugs that affect the ability of your bone marrow to make blood cells.

For people with heart disease: If you have heart disease, taking this drug may make it worse. This drug can cause the rhythm of your heart to be abnormal.

For people with liver disease: When your body gets rid of this drug, it first breaks it down in your liver. If you have liver disease, your liver can’t break down the drug as quickly as it should. This means the level of this drug in your body could get too high. This raises your risk of side effects.

For people with breathing problems: This drug may thicken the secretions in your breathing tubes. If you have asthma or chronic obstructive pulmonary disease (COPD), this may cause an asthma attack or make your COPD worse. The drug should not be taken during an acute asthma attack or if you have COPD.

For people with sleep apnea: This drug may thicken the secretions in your breathing tubes. If you have sleep apnea, taking this drug at night may worsen your condition.

For people with seizures: This drug raises your risk of seizures. Talk to your doctor if you take other drugs that can cause seizures. Taking these drugs together can increase this risk.

Warnings for other groups

For pregnant women: Promethazine is a category C pregnancy drug. That means two things:

  1. Research in animals has shown adverse effects to the fetus when the mother takes the drug.
  2. There haven’t been enough studies done in humans to be certain how the drug might affect the fetus.

Talk to your doctor if you’re pregnant or planning to become pregnant. This drug should be used only if the potential benefit justifies the potential risk to the fetus.

This drug should not be given to a pregnant woman within 2 weeks of delivery because it raises her risk of bleeding.

For women who are breastfeeding: Promethazine may pass into breast milk and may cause side effects in a child who is breastfed. Talk to your doctor if you breastfeed your child. You may need to decide whether to stop breastfeeding or stop taking this drug.

For seniors: Seniors may be more sensitive to the sedating effects of this drug. They may be more likely to experience severe drowsiness, reduced mental alertness, and confusion.

For children:

  • This drug should not be used in children younger than 2 years. In children this age, this drug may cause slowed breathing that could be fatal. Caution should also be used when giving this drug to children older than 2 years.
  • This drug should not be used in children who are taking other drugs that may cause slowed breathing.
  • This drug is not recommended to treat uncomplicated vomiting in children. It should only be used for extended periods of vomiting when the cause is known.
  • Some children who have taken this drug at the recommended dosages have had hallucinations and seizures. If children have a temporary illness, such as a cold or the flu, and take this drug, their risk of involuntary muscle contractions increases.
  • Excessive large doses of this drug in children may cause sudden death.

How to take promethazine

All possible dosages and drug forms may not be included here. Your dosage, drug form, and how often you take the drug will depend on:

  • your age
  • the condition being treated
  • how severe your condition is
  • other medical conditions you have
  • how you react to the first dose

Forms and strengths

Generic: Promethazine

  • Form: oral tablet
  • Strengths: 12.5 mg, 25 mg, 50 mg

Dosage for allergies

Adult dosage (ages 18–64 years)

  • The average dose is 25 mg, taken at bedtime, or 12.5 mg, taken every 4 hours, right before meals.
  • Your dosage may be decreased by your doctor to the smallest amount that still works.
  • When using this drug to control allergic reactions to blood or plasma, the usual dose is 25 mg.

Child dosage (ages 2–17 years)

  • The average daily dose is 25 mg, taken at bedtime, or 12.5 mg, taken every 4 hours, right before meals.
  • Your dosage may be decreased by your doctor to the smallest amount that still works.
  • When using this drug to control allergic reactions to blood or plasma, the usual dose is 25 mg.

Child dosage (ages 0–23 months)

It has not been confirmed that promethazine is safe and effective for use in children younger than 2 years.

Senior dosage (ages 65 years and older)

  • The liver, kidneys, and hearts of older adults may not work as well as they used to. This can cause your body to process drugs more slowly. As a result, more of a drug stays in your body for a longer time. This increases your risk of side effects.
  • Your doctor may start you on a lower dose or a different medication schedule. This can help keep levels of this drug from building up too much in your body.

Dosage for motion sickness

Adult dosage (ages 18–64 years)

  • The average dose is 25 mg, twice daily.
  • The initial dose should be taken 30 minutes to 1 hour before travel. A second dose can be taken 8–12 hours later, if needed.
  • On the following days of travel, it is recommended to take 25 mg once you get up in the morning and again before your last meal of the day.

Child dosage (ages 2–17 years)

  • The average dose is 12.5–25 mg, taken twice daily.
  • The initial dose should be taken 30 minutes to 1 hour before travel. A second dose can be taken 8–12 hours later, if needed.
  • On following days of travel, it is recommended to take 12.5–25 mg right after you get up in the morning and again before your last meal of the day.

Child dosage (ages 0–23 months)

It has not been confirmed that promethazine is safe and effective for use in children younger than 2 years.

Senior dosage (ages 65 years and older)

  • The liver, kidneys, and hearts of older adults may not work as well as they used to. This can cause your body to process drugs more slowly. As a result, more of a drug stays in your body for a longer time. This increases your risk of side effects.
  • Your doctor may start you on a lower dose or a different medication schedule. This can help keep levels of this drug from building up too much in your body.

Dosage for nausea and vomiting

Adult dosage (ages 18–64 years)

  • For active nausea and vomiting, the average dose is 25 mg. Between 12.5 mg and 25 mg may be taken again every 4–6 hours, if needed.
  • For preventing nausea and vomiting, the average dose is 25 mg every 4–6 hours as needed.

Child dosage (ages 2–17 years)

  • For nausea and vomiting, the usual dose is 0.5 mg per kilogram of body weight.
  • The dose will be adjusted to the age and weight of the child and the severity of their condition.

Child dosage (ages 0–23 months)

It has not been confirmed that promethazine is safe and effective for use in children younger than 2 years.

Senior dosage (ages 65 years and older)

  • The liver, kidneys, and hearts of older adults may not work as well as they used to. This can cause your body to process drugs more slowly. As a result, more of a drug stays in your body for a longer time. This increases your risk of side effects.
  • Your doctor may start you on a lower dose or a different medication schedule. This can help keep levels of this drug from building up too much in your body.

Dosage for use as a sleep aid

Adult dosage (ages 18–64 years)

The usual dose is 25–50 mg.

Child dosage (ages 2–17 years)

The usual dose is 12.5–25 mg.

Child dosage (ages 0–23 months)

It has not been confirmed that promethazine is safe and effective for use in children younger than 2 years.

Senior dosage (ages 65 years and older)

  • The liver, kidneys, and hearts of older adults may not work as well as they used to. This can cause your body to process drugs more slowly. As a result, more of a drug stays in your body for a longer time. This increases your risk of side effects.
  • Your doctor may start you on a lower dose or a different medication schedule. This can help keep levels of this drug from building up too much in your body.

Dosage for use as anxiety treatment or sleep aid before surgery

Adult dosage (ages 18–64 years)

The night before surgery, the usual dose is 50 mg to relieve anxiety and promote sleep.

Child dosage (ages 2–17 years)

The night before surgery, the usual dose is 12.5–25 mg to relieve anxiety and promote sleep.

Child dosage (ages 0–23 months)

It has not been confirmed that promethazine is safe and effective for use in children younger than 2 years.

Senior dosage (ages 65 years and older)

  • The liver, kidneys, and hearts of older adults may not work as well as they used to. This can cause your body to process drugs more slowly. As a result, more of a drug stays in your body for a longer time. This increases your risk of side effects.
  • Your doctor may start you on a lower dose or a different medication schedule. This can help keep levels of this drug from building up too much in your body.

Dosage for use as anxiety treatment or sleep aid after surgery

Adult dosage (ages 18–64 years)

After surgery, the usual dose is 25–50 mg to promote sleep and for use with other pain medications.

Child dosage (ages 2–17 years)

After surgery, the usual dose is 12.5–25 mg to promote sleep and for use with other pain medications.

Child dosage (ages 0–23 months)

It has not been confirmed that promethazine is safe and effective for use in children younger than 2 years.

Senior dosage (ages 65 years and older)

  • The liver, kidneys, and hearts of older adults may not work as well as they used to. This can cause your body to process drugs more slowly. As a result, more of a drug stays in your body for a longer time. This increases your risk of side effects.
  • Your doctor may start you on a lower dose or a different medication schedule. This can help keep levels of this drug from building up too much in your body.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this list includes all possible dosages. This information is not a substitute for medical advice. Always to speak with your doctor or pharmacist about dosages that are right for you.

Take as directed

Promethazine is used for short-term treatment. It comes with risks if you don’t take it as prescribed.

If you stop taking the drug or don’t take it at all

If you’re using this drug for allergies or an allergic reaction, your allergic symptoms such as sneezing, runny nose, itching, eye tearing, and hives may recur and worsen. If you’re taking promethazine to prevent or treat nausea and vomiting, motion sickness, pain, or to lessen anxiety and promote sleep, you may not experience relief of your symptoms.

If you miss doses or don’t take the drug on schedule

Your medication may not work as well or may stop working completely. For this drug to work well, a certain amount needs to be in your body at all times.

If you take too much

You could have dangerous levels of the drug in your body. If you think you’ve taken too much of the drug, act right away. Call your doctor or local poison control center, or go to the nearest emergency room.

What to do if you miss a dose

Take your dose as soon as you remember. But if you remember just a few hours before your next scheduled dose, take only one dose. Never try to catch up by taking two doses at once. This could result in dangerous side effects.

How to tell if the drug is working

If you’re using this drug for allergies or an allergic reaction, your symptoms, such as sneezing, runny nose, itching, eye tearing, and hives, should decrease or stop. If you’re taking this drug to prevent or treat nausea and vomiting, motion sickness, pain, or to lessen anxiety and promote sleep, you should experience relief of your symptoms.

Important considerations for taking promethazine

Keep these considerations in mind if your doctor prescribes promethazine for you.

General

  • You can take this drug with or without food. Taking it with food may help to reduce upset stomach.
  • You can cut or crush this tablet.
  • Not every pharmacy stocks this drug. When filling your prescription, be sure to call ahead.

Storage

  • Store promethazine tablets at room temperature between 68°F and 77°F (20°C and 25°C).
  • Keep it away from light.
  • Don’t store this medication in moist or damp areas, such as bathrooms.

Refills

A prescription for this medication is refillable. You should not need a new prescription for this medication to be refilled. Your doctor will write the number of refills authorized on your prescription.

Travel

When traveling with your medication:

  • Always carry your medication with you. When flying, never put it into a checked bag. Keep it in your carry-on bag.
  • Don’t worry about airport x-ray machines. They can’t hurt your medication.
  • You may need to show airport staff the pharmacy label for your medication. Always carry the original prescription-labeled box with you.
  • Don’t put this medication in your car’s glove compartment or leave it in the car. Be sure to avoid doing this when the weather is very hot or very cold.

Sun sensitivity

This drug can make your skin more sensitive to the sun. This increases your risk of sunburn. Avoid the sun if you can. If you can’t, be sure to wear protective clothing and apply sunscreen.

Insurance

Some insurance companies require a prior authorization for this drug. This means your doctor will need to get approval from your insurance company before your insurance company will pay for the prescription.

Are there any alternatives?

There are other drugs available to treat your condition. Some may be better suited for you than others. Talk to your doctor about other drug options that may work for you.

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up-to-date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or other healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.

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