Promethazine

Aka: Promethazine, Phenergan

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II. Indications

  1. Nausea or Vomiting
  2. Motion Sickness or Vertigo
    1. Other agents are preferred (e.g. Dimenhydrinate)

III. Mechanism

  1. Phenothiazine Antiemetic
  2. Dopamine 2 Antagonist
    1. Active at the ChemoreceptorTrigger Zone in the Medulla of the Brainstem
    2. Similar to other DopamineAntagonist Antipsychotic agents

IV. Contraindications

  1. Do not use under age 2 years

V. Adverse Effects

  1. Respiratory Depression
    1. Apnea and death have occurred in children
  2. Severe tissue injury risk on Parenteral Injection
    1. Do not use Subcutaneous Injection
  3. Hypotension with rapid IV injection
  4. Extrapyramidal Side Effects (with high IV dose)
  5. Anticholinergic effects (e.g. sedation, Dry Mouth)

VI. Safety

  1. Pregnancy Category C
  2. Avoid in Lactation

VII. Precautions

  1. Long plasma Half-Life (observe prior to discharge)
  2. Lowers Seizure threshold
  3. Avoid use in children due to respiratory depression
    1. Absolutely contraindicated <2 years old

VIII. Dosing: Adults

  1. Nausea or Vomiting
    1. PO/PR/IM: 12.5 to 25 mg PO/Deep IM/PR every 4 to 6 hours
    2. IV (not FDA labeled, see adverse effects): 12.5 to 25 mg IV every 4 hours as needed
  2. Motion Sickness
    1. PO/PR: 25 mg orally or PR 30 to 60 minutes prior to departure and every 12 hours as needed

IX. Dosing: Children (over age 2 years only)

  1. Children
    1. PO/PR/IM: 0.25 to 0.5 mg/kg (up to 25 mg/dose) PO/deep IM/PR every 4 to 6 hours
    2. IV (not FDA labeled, see adverse effects): 0.25 mg/kg/dose (up to 25 mg) IV every 4 hours as needed
  2. Motion Sickness
    1. PO/PR: 0.5 mg/kg (up to 25 mg/dose) PO/PR 30 to 60 minutes prior to departure and every 12 hours as needed

X. Efficacy

  1. Less effective Antiemetic than Prochlorperazine (Compazine) in ER patients
    1. Ernst (2000) Ann Emerg Med 36(2): 89-94 [PubMed]
  2. Sedation may delay Emergency Department discharge

XI. Resources

  1. Promethazine (DailyMed)
    1. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=b0d5abba-6fae-4f3c-b990-dd9c83c7b5a9

XII. References

  1. Johnson (1993) Harriet Lane, Mosby, p. 521
  2. Hamilton (2020) Tarascon Pocket Pharmacopoeia

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