promethazine hydrochloride

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promethazine hydrochloride

Avomine (UK), Histantil (CA), Phenergan (CA), PMS-Promethazine, Promethegan, Sominex (UK), Ziz (UK)

Pharmacologic class: Phenothiazine (nonselective)

Therapeutic class: Antihistamine, antiemetic, sedative-hypnotic

Pregnancy risk category C

FDA Box Warning

• Don't use promethazine in patients younger than age 2 due to potential for fatal respiratory depression. (Postmarketing cases of respiratory depression have been reported in these patients.)

• Use caution when administering to pediatric patients age 2 years and older. Preferably, use lowest effective dosage in these patients and avoid concurrent use of other drugs with respiratory depressant effects.

• Promethazine injection can cause severe chemical irritation and damage to tissue regardless of administration route. Irritation and damage can result from perivascular extravasation, unintentional intra-arterial injection, and intraneuronal or perineuronal infiltration.

• Adverse reactions to I.V. injection include burning, pain, thrombophlebitis, tissue necrosis, and gangrene. In some cases, surgical intervention, including fasciotomy, skin graft, or amputation, has been required.

• Because of risks of I.V. injection, preferred parenteral administration route is deep I.M. injection. Subcutaneous injection is contraindicated.


Blocks effects but not release of histamine and exerts strong alphaadrenergic effect. Also inhibits chemoreceptor trigger zone in medulla and alters dopamine effects by indirectly reducing reticular stimulation in CNS.


Injection: 25 mg/ml and 50 mg/ml in 1-ml ampules and 1- and 10-ml vials

Suppositories: 12.5 mg, 25 mg, 50 mg

Syrup: 6.25 mg/5 ml

Tablets: 12.5 mg, 25 mg, 50 mg

Indications and dosages

Type 1 hypersensitivity reaction

Adults: 25 mg P.O. or P.R. at bedtime or 12.5 mg P.O. before meals and at bedtime. Or 25 mg I.M. or I.V.; may repeat in 2 hours.

Children older than age 2: 25 mg P.O. or P.R. at bedtime or 6.25 to 12.5 mg P.O. t.i.d.

Motion sickness

Adults: Initially, 25 mg P.O. or P.R. 30 to 60 minutes before traveling; may repeat 8 to 12 hours later if needed. On successive travel days, 25 mg P.O. or P.R. b.i.d. (on arising and before evening meal).

Children older than age 2: 12.5 to 25 mg P.O. or P.R. b.i.d.


Adults: 25 to 50 mg P.O., I.M., I.V., or P.R. at bedtime

Children older than age 2: 12.5 to 25 mg P.O. or P.R. at bedtime

Adjunct to preoperative or postoperative analgesia

Adults: 25 to 50 mg P.O., P.R., I.M., or I.V. given with appropriately reduced dosage of narcotic or barbiturate and required dosage of belladonna alkaloid

Children older than age 2: 0.5 mg/lb P.O., P.R., I.M., or I.V., given with appropriately reduced dosage of narcotic or barbiturate and required dosage of belladonna alkaloid


Adults: 25 mg P.O. or P.R.; may repeat doses of 12.5 to 25 mg P.O. or P.R. q 4 to 6 hours p.r.n. Or 12.5 to 25 mg I.M. or I.V.; may repeat q 4 hours p.r.n.

Children older than age 2: 25 mg or 0.5 mg/lb P.O. or P.R.; may repeat doses of 12.5 to 25 mg P.O. or P.R. q 4 to 6 hours p.r.n. May give I.M. or I.V. as no more than half of adult dosage. Know that drug should not be given if cause of vomiting is unknown.


• Hypersensitivity to drug
• Previous idiosyncratic reaction to phenothiazines
• Coma
• Intra-arterial and subcutaneous injection
• Children younger than age 2


Use cautiously in:
• cardiovascular or hepatic disease, seizures, bone marrow depression, narrow-angle glaucoma, prostatic hypertrophy, stenosing peptic ulcer, pyloroduodenal or bladder neck obstruction
• CNS depression caused by narcotics, barbiturates, general anesthesia, tranquilizers, or alcohol
• pregnant or breastfeeding patients.


• Don't give I.V. at concentrations greater than 25 mg/ml or faster than 25 mg/minute.
• Use light-resistant covering for I.V. drug.

Inject I.M. deep into large muscle. Don't give by subcutaneous route.

Adverse reactions

CNS: confusion, disorientation, fatigue, marked drowsiness, sedation, dizziness, extrapyramidal reactions, insomnia, nervousness, neuroleptic malignant syndrome

CV: hypertension, hypotension, bradycardia, tachycardia

EENT: blurred vision, diplopia, tinnitus

GI: constipation, dry mouth

Hematologic: blood dyscrasias

Hepatic: cholestatic jaundice

Respiratory: respiratory depression

Skin: photosensitivity, rash

Other: hypersensitivity reaction


Drug-drug.Anticholinergics: additive anticholinergic effects

CNS depressants: additive CNS depression

Epinephrine: reversal of epinephrine's vasopressor effects

MAO inhibitors: increased extrapyramidal effects

Drug-diagnostic tests.Glucose: increased level

Granulocytes, platelets, white blood cells: decreased counts

Pregnancy test: false-positive or false-negative result

Skin tests using allergen extracts: false-negative results

Drug-herbs.Betel nut: increased risk of extrapyramidal reactions

Evening primrose oil: increased risk of seizures

Kava: increased risk of adverse drug effects

Drug-behaviors.Alcohol use: additive CNS depression

Sun exposure: increased risk of photosensitivity

Patient monitoring

Monitor neurologic status. Stay alert for signs and symptoms of neuroleptic malignant syndrome (high fever, sweating, unstable blood pressure, stupor, muscle rigidity, and autonomic dysfunction).
• In long-term therapy, assess for other adverse CNS effects, including extrapyramidal reactions.
• Monitor CBC and liver function tests.

Patient teaching

Teach patient to recognize and immediately report signs and symptoms of hypersensitivity reaction or neuroleptic malignant syndrome.
• Tell patient about drug's other significant neurologic effects. Instruct him to contact prescriber if these occur.
• Caution patient to avoid driving and other hazardous activities until he knows how drug affects concentration, vision, alertness, and motor skills.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, herbs, and behaviors mentioned above.

promethazine hydrochloride

(prō-mĕth′ə-zēn′, -zĭn)
An antihistamine with sedative properties, used to treat allergic rhinitis and other allergic reactions, to prevent and treat motion sickness, and as a sedative and antiemetic.

promethazine hydrochloride

a phenothiazine antiemetic, antihistamine, and sedative.
indications It is prescribed in the treatment of motion sickness, nausea, rhinitis, itching, and skin rash and as an adjunct to anesthesia and pain control.
contraindications Known hypersensitivity to this drug or to other phenothiazines or severe central nervous system depression or coma prohibits its use.
adverse effects Drowsiness, hypotension, and dry mouth are the most common adverse effects.