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Promethazine oral forms dosage: A detailed guide

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Forms and strengthsDosageFAQsHow it’s takenCouponOverdoseAsk your doctorBoxed warning
Promethazine oral forms are prescribed for several conditions in adults and certain children. The conditions include allergies, motion sickness, nausea, and vomiting. The oral forms are taken by mouth up to six times per day for certain conditions.
Medically reviewed by Victor Nguyen, PharmD, MBA
Updated on April 3, 2023

Promethazine oral forms are generic medications. They’re not available in a brand-name version. Promethazine also comes in an injectable form and a suppository that’s inserted into the rectum. But those forms aren’t described in this article. To learn more about them, talk with your doctor.

This article describes promethazine oral forms’ dosages, their strengths, and details on how to take them. You’ll also find information on cost savings and coupon options for promethazine.

If you want to know more about promethazine oral forms, see this overview article. It covers details about the drug’s uses, side effects, and more.

Boxed warning: Risk of breathing problems in young children

Promethazine oral forms have a boxed warning for the risk of breathing problems in young children. Boxed warnings are serious warnings from the Food and Drug Administration (FDA).

See the end of this article for more information about this warning.

Forms and strengths of promethazine

Promethazine oral forms come as follows:

Forms and strengths:

  • Tablet that you swallow: 25 milligrams (mg)
  • Liquid solution that you swallow: 6.25 mg per 5 milliliters (mg/mL)
  • Syrup that you swallow: 6.25 mg/5 mL

Dosage of promethazine

This article describes the recommended dosages* for promethazine oral forms.

If your doctor prescribes this medication, you should take the dosage they prescribe. Your doctor will determine the dosage that best meets your needs. Do not change your dosage of promethazine oral forms without your doctor’s recommendation.

* The drugmaker provides these recommended dosages.

Usual recommended dosages of promethazine in adults

The information below describes dosages that are commonly prescribed for adults. Your doctor will determine the maximum dosage to take in 24 hours, if needed. Doses are measured in milligrams (mg).

PurposeDosage
treat allergy• 25 mg at bedtime, or
• 12.5 mg before meals and at bedtime, as needed, or
• 6.25 mg to 12.5 mg, taken 3 times per day
treat motion sickness25 mg, twice per day
treat nausea and vomiting12.5 mg to 25 mg every 4 to 6 hours
promote restful sleep25 mg to 50 mg at bedtime
promote restful sleep and reduce anxiety before or after surgery• 50 mg the night before surgery
• 50 mg before surgery
• 25 mg to 50 mg after surgery

Dosages of promethazine in children

Promethazine oral forms are approved for use in children who are ages 2 years and older.

The drug has a boxed warning for the risk of breathing problems in young children. For details about this warning, see the “Boxed warning for promethazine” section below.

The following table describes dosages that are commonly prescribed for children.

PurposeDosage
treat allergy• 25 mg at bedtime, or
• 12.5 mg before meals and at bedtime, as needed, or
• 6.25 mg to 12.5 mg, taken 3 times per day
treat motion sickness12.5 mg to 25 mg, twice per day
treat nausea and vomiting0.5 mg per pound of body weight* every 4 to 6 hours, as needed
promote restful sleep12.5 mg to 25 mg at bedtime
promote restful sleep and reduce anxiety before or after surgery• 12.5 mg to 25 mg the night before surgery
• 0.5 mg per pound of body weight* before surgery†
• 12.5 mg to 25 mg after surgery†

* For example, assume a doctor prescribes promethazine for a 3-year-old child who weighs 33 pounds (lb). The child’s dosage would be 16.5 mg.
† For promoting restful sleep and reducing anxiety before or after surgery, doses are to be given as prescribed by the doctor or surgeon.

Dosage adjustments for promethazine

Your doctor will prescribe a dosage of promethazine oral forms based on several factors. These include:

  • the specific condition being treated and the severity
  • your age
  • your other health conditions
  • how your body responds to the drug

Missed dose of promethazine

Talk with your doctor or pharmacist right away if you realize you forgot to take a dose of promethazine oral forms. They may advise you to take the missed dose. Or they may advise you to skip it and take your next dose as scheduled.

For tips on how to plan your doses of promethazine oral forms and avoid missing a dose, read this article. You could also try:

  • downloading a reminder app on your phone
  • setting an alarm
  • putting a note where you’ll see it, such as on your calendar, bathroom mirror, or bedside table

Frequently asked questions

Below are answers to some commonly asked questions about promethazine oral forms and their dosages.

How does the injection dosage of promethazine compare with the oral forms’ dosage?

Promethazine is available in an injectable form. It comes in two strengths: 25 milligrams per milliliter (mg/mL) and 50 mg/mL. The dosage for the injectable form is similar to the dosage for the oral forms.

If you’d like to learn more about the injectable form of promethazine, talk with your doctor or pharmacist.

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Will my child’s dose of promethazine be calculated by weight?

It depends on the condition your child’s doctor is treating. The recommended dosages of promethazine for treating most conditions in children are specific. But the recommended dosage for nausea and vomiting is based on a child’s body weight.

For more information, see “Dosages of promethazine in children” in the “Dosage of promethazine” section above.

If you have questions or concerns about your child’s dosage, talk with your doctor or pharmacist.

Is promethazine taken long term?

No, doctors don’t typically prescribe promethazine oral forms as a long-term treatment. Instead, it’s usually recommended for short-term use.

If you have questions about how long you should take promethazine oral forms, talk with your doctor.

How promethazine is taken

Promethazine oral forms are swallowed. You’ll take the form as prescribed, including the dose and frequency your doctor determines.

You can take promethazine oral forms with food or without it.

If you need to, you can cut or crush the oral tablet form. If it’s hard for you to swallow tablets, view this article. It provides suggestions on how to swallow medications that come in pill form.

Also, be sure to talk with your doctor or pharmacist if you’re having difficulty taking your medication. They can offer recommendations about taking it.

Promethazine coupon

Visit this page to access Optum Perks coupons and get price estimates for promethazine when you use the coupons. These coupons can provide significant savings on your prescription costs. 

Note: Optum Perks coupons cannot be used with any insurance copays or benefits.

Overdose of promethazine

It’s important that you do not take more promethazine oral forms than your doctor prescribes. Doing so can lead to serious side effects.

Symptoms of promethazine overdose

Symptoms of an overdose can include:

  • low blood pressure
  • confusion or problems with memory or concentration
  • abnormal muscle contractions
  • loss of consciousness
  • muscle stiffness
  • overactive reflexes
  • poor balance or coordination
  • slow or shallow breathing

What to do if you take too much promethazine

If you think you’ve taken too much promethazine, call your doctor or pharmacist right away. Or you could call 800-222-1222 to speak with someone at America’s Poison Centers. You can also use its online resource. If you have severe symptoms, call 911 or a local emergency number immediately. You can also go to the closest emergency room.

What to ask your doctor

This article describes the usual recommended dosages for promethazine oral forms. If your doctor prescribes this medication, they’ll determine the dosage that’s best for you.

Do not change your dosage of promethazine oral forms without your doctor’s recommendation. You should take promethazine oral forms exactly as your doctor prescribes them. Let your doctor know if you have concerns or questions about your treatment plan.

Here’s a list of some possible questions you may want to ask your doctor:

  • Does my dose of promethazine oral forms need to change if I take other medications?
  • How soon will I know if my dosage of promethazine oral forms is working?
  • How long should I take promethazine oral forms?

Boxed warning for promethazine

Promethazine oral forms have a boxed warning for the risk of breathing problems in young children. Boxed warnings are serious warnings from the Food and Drug Administration (FDA).

Promethazine oral forms should not be given to children younger than age 2 years. This is because the drug can cause slow or shallow breathing that can be fatal.

In children ages 2 years and older, promethazine oral forms should be given with caution. They should not be given together with other drugs that can cause slow or shallow breathing.

You can talk with your child’s doctor to learn more about this warning.

Disclaimer: Optum Perks 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 another 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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