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Supportive Care

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What is promethazine?

Promethazine (also called Phenergan®) is used to treat nausea and vomiting. Promethazine is available in these forms:

  • 12.5 mg, 25 mg, and 50 mg tablets taken by mouth
  • 1.25 mg/ml and 5 mg/ml syrup (liquid) taken by mouth
  • 12.5 mg, 25 mg, and 50 mg suppositories inserted into the rectum
  • 50 mg/ml liquid given by vein
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Possible side effects

  • Feeling drowsy
  • Dry mouth or throat

    Call the doctor right away if you have any of these severe side effects:
  • Trouble breathing
  • Fast, slow, or irregular heart beat
  • Skin rash, itching, or hives
  • Convulsions
  • Uncontrolled movements of the eyes, neck, or tongue
  • These are the most common side effects, but there may be others. Please report all side effects to the doctor or nurse.

Symptoms of an allergic reaction include: rash, hives, itching, chills, fever, headache, muscle ache, shortness of breath, coughing, tightness in the throat, swelling of the face or neck.

Not all patients who take promethazine will experience these side effects. Common side effects are bolded, but there may be others. Please report all suspected side effects to your doctor or pharmacist.

Find more information on side effects.

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Tips for patients and families

Be sure to discuss all questions and instructions with your doctor or pharmacist. 

Stop taking promethazine if you have a severe side effect (listed above).

  • Do not take promethazine if you have had an allergic reaction to any of these medicines:
    • Prochlorperazine (Compazine®)
    • Chlorpromazine (Thorazine®)
    • Thioridazine (Mellaril®)
  • Because promethazine may cause you to feel drowsy, you should not drive, operate machinery, or perform any hazardous activity until you see how your body responds to this medicine.
  • This medicine can increase the risk of falls.

Drug at Home:

Your doctor will tell you how much promethazine to take and how often to take it.

  • Syrup and tablets
    • You may take the tablets or syrup with food or milk to avoid an upset stomach.
    • Store the tablets and syrup at room temperature. Store them away from light, heat, and moisture.
  • Rectal suppositories
    • Never take suppositories by mouth. Insert the suppository into the rectum after removing the wrapper.
    • You may wet the rectum with water to make it easier to insert the suppository. Do not apply any petroleum jelly (Vaseline®) to the rectum before you insert the suppository.
    • Place the pointed end of the suppository into the rectum, and push gently until it is all the way inside.
    • Wash your hands with soap and water after you have inserted the suppository.
    • Store the suppositories in a tightly closed container in the refrigerator.