PROMETHAZINE

Phenothiazine with antihistamine, anti-emetic, anti-allergic, and sedative activity

Dosage Forms

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Tablet

25 mg

Injection

25 mg/ml

Uses

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  • Relieve itching in allergic reactions
  • Nausea and vomiting (drug-induced, excessive vomiting in pregnancy, post-operative nausea)
  • Motion sickness
  • Vertigo
  • Anaphylactic shock

Dose and Duration

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Allergic reactions and itching, nausea, vomiting, vertigo

Adult: 25 mg orally at night, increased if necessary to every 12 hours

Child: 1 mg/kg daily in 1–2 divided doses

Excessive vomiting of pregnancy

25 mg IM once daily OR by mouth, every 8 hours prn

Motion sickness prevention

Adult: 20–25 mg orally

Child 2–5 years: 5 mg

Child 5–10 years: 10 mg

Take at bedtime on the night before travel and repeat the following morning if necessary

Anaphylactic shock

Adult: 25–50 mg by deep IM or slow IV over 1 minute (max 100 mg in 24 hours). Use diluted solution.

Child 5–10 years: 6.25–12.5 mg by deep IM

Child 1-5 years: 0.5 ml/kg by deep IM

Repeat dose every 8 hours for 24–48 hours

Preparation

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  • Dilute each 1 ml of promethazine injection 25 mg/ml with 9 ml of water for injection

Contraindications

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  • Children <1 year
  • Glaucoma
  • Urinary and prostate disorders
  • Severe liver disease

Side Effects

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  • Drowsiness, dizziness, sedation, headache
  • Nightmares, confusion
  • Movement disorders
  • Dry mouth, constipation
  • Urinary retention
  • Blurred vision
  • Rash
  • Jaundice
  • Blood disorders
  • Pain at injection site
  • Risk of limb gangrene after injection
  • Respiratory depression

Interactions

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Increased risk of sedation and respiratory depression when given with:

  • Morphine
  • Diazepam
  • Alcohol
  • Amitriptyline

Patient Instructions

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  • Take medicine preferably at night in a single dose
  • Causes sleepiness; do not operate machinery or drive while taking the medicine
  • Do not drink alcohol during treatment
  • Do not take larger doses than prescribed

Pregnancy

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  • Do not use in 3rd trimester

Breast-feeding

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  • Do not use

⚠️ Caution

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  • Promethazine has little effect in nausea and vomiting caused by anti-cancer medicines
  • Use with caution in liver disease, epilepsy, the elderly, and children as they are more susceptible to side effects