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Back to Drug index

Back to Antiemetics

Name: Promethazine hydrochloride

Pregnancy Category C

Drug classes

  • Antiemetic
  • Phenothiazine
  • Dopaminergic blocking drug
  • Antihistamine
  • Antimotion sickness drug
  • Sedative

Therapeutic actions

Selectively blocks H1 receptors, diminishing the effects of histamine on cells of the upper respiratory tract and eyes and decreasing the sneezing, mucus production, itching, and tearing that accompany allergic reactions in sensitized people exposed to antigens; blocks cholinergic receptors in the vomiting center that are believed to mediate the nausea and vomiting caused by gastric irritation, by input from the vestibular apparatus (motion sickness, nausea associated with vestibular neuritis), and by input from the chemoreceptor trigger zone (drug- and radiation-induced emesis); depresses the reticular activating system, including the parts of the brain involved with wakefulness.


Symptomatic relief of symptoms associated with perennial and seasonal allergic rhinitis, vasomotor rhinitis, allergic conjunctivitis; mild, uncomplicated urticaria and angioedema; amelioration of allergic reactions to blood or plasma; dermatographism, adjunctive therapy (with
epinephrine and other measures) in anaphylactic reactions

Treatment and prevention of motion sickness; prevention and control of nausea and vomiting associated with anesthesia and surgery

Preoperative, postoperative, or obstetric sedation

Adjunct to analgesics to control postoperative pain

Adjunctive IV therapy with reduced amounts of meperidine or other narcotic analgesics in special surgical situations, such as repeated bronchoscopy, ophthalmic surgery, or in poor-risk patients


Contraindicated in the presence of hypersensitivity to antihistamines or phenothiazines, coma or severe CNS depression, bone marrow depression, vomiting of unknown cause, concomitant therapy with MAOIs, lactation (lactation may be inhibited).

Use caution in the presence of lower respiratory tract disorders (drug may cause thickening of secretions and impair expectoration), glaucoma, prostatic hypertrophy, cardiovascular disease or hypertension, breast cancer, thyrotoxicosis, pregnancy (jaundice and extrapyramidal symptoms have been reported in infants whose mothers received phenothiazines during pregnancy; drug may inhibit platelet aggregation in neonate if taken by mother within 2 wk of delivery), children (antihistamine overdosage may cause hallucinations, convulsions, and death), a child with a history of sleep apnea, a family history of sudden infant death syndrome, or Reye's syndrome (drug may mask the symptoms of Reye's syndrome and contribute to its development), the elderly (more likely to cause dizziness, sedation, syncope, toxic confusional states, hypotension, and extrapyramidal effects in the elderly).

Adverse effects

  • CNS: Dizziness, drowsiness, poor coordination, confusion, restlessness, excitation, convulsions, tremors, headache, blurred vision, diplopia, vertigo, tinnitus
  • GI: Epigastric distress, nausea, vomiting, diarrhea, constipation
  • CV: Hypotension, palpitations, bradycardia, tachycardia, extrasystoles
  • Respiratory: Thickening of bronchial secretions; chest tightness; dry mouth, nose, and throat; respiratory depression; suppression of cough reflex, potential for aspiration
  • Hematologic: Hemolytic anemia, hypoplastic anemia, thrombocytopenia, leukopenia, agranulocytosis, pancytopenia
  • GU: Urinary frequency, dysuria, urinary retention, decreased libido, impotence
  • Dermatologic: Urticaria, rash, photosensitivity, chills
  • Other: Tingling, heaviness and wetness of the hands
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