July 24, 2016
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Promethazine HCl Injection

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Promethazine HCl Injection

Side Effects


CNS Effects

Drowsiness is the most prominent CNS effect of the drug. Extrapyramidal reactions may occur with high doses; this is almost always responsive to a reduction in dosage. Other reported reactions include dizziness, lassitude, tinnitus, incoordination, fatigue, blurred vision, euphoria, diplopia, nervousness, insomnia, tremors, convulsive seizures, oculogyric crises, excitation, catatonic-like states, hysteria, and hallucinations.

Cardiovascular Effects

Tachycardia, bradycardia, faintness, dizziness, and increases and decreases in blood pressure have been reported following the use of promethazine hydrochloride (promethazine hydrochloride injection) . Venous thrombosis at the injection site has been reported. INTRA-ARTERIAL INJECTION MAY RESULT IN GANGRENE OF THE AFFECTED EXTREMITY. (See WARNINGS, Inadvertent Intra-arterial Injection.)

Gastrointestinal Effects

Nausea and vomiting have been reported, usually in association with surgical procedures and combination drug therapy.

Allergic Reactions

These include urticaria, dermatitis, asthma, and photosensitivity. Angioneurotic edema has been reported.

Other Reported Reactions

Leukopenia and agranulocytosis, usually when promethazine has been used in association with other known marrow-toxic agents, have been reported. Thrombocytopenic purpura and jaundice of the obstructive type have been associated with the use of promethazine. The jaundice is usually reversible on discontinuation of the drug. Subcutaneous injection has resulted in tissue necrosis. Nasal stuffiness may occur. Dry mouth has been reported.

Paradoxical Reactions (Overdosage)

Hyperexcitability and abnormal movements, which have been reported in pediatric patients following a single administration of promethazine hydrochloride (promethazine hydrochloride injection) , may be manifestations of relative overdosage, in which case, consideration should be given to the discontinuation of promethazine hydrochloride (promethazine hydrochloride injection) and to the use of other drugs. Respiratory depression, nightmares, delirium, and agitated behavior have also been reported in some of these patients.

Read the Promethazine HCl Injection (promethazine hydrochloride injection) Side Effects Center for a complete guide to possible side effects


CNS Depressants

Promethazine hydrochloride (promethazine hydrochloride injection) may increase, prolong, or intensify the sedative action of central-nervous-system depressants, such as alcohol, sedative-hypnotics (including barbiturates), general anesthetics, narcotics, narcotic analgesics, tranquilizers, etc. When given concomitanty with promethazine hydrochloride (promethazine hydrochloride injection) , the dose of barbiturates should be reduced by at least one-half, and the dose of narcotics should be reduced by one-quarter to one-half. Dosage must be individualized. Excessive amounts of promethazine hydrochloride (promethazine hydrochloride injection) relative to a narcotic may lead to restlessness and motor hyperactivity in the patient with pain; these symptoms usually disappear with adequate control of the pain.


Although reversal of the vasopressor effect of epinephrine has not been reported with promethazine hydrochloride (promethazine hydrochloride injection) , it is recommended that epinephrine NOT be used in the case of promethazine hydrochloride (promethazine hydrochloride injection) overdose.


Concomitant use of other agents with anticholinergic properties should be undertaken with caution.

Monoamine Oxidase Inhibitors (MAOI)

Drug interactions, including an increased incidence of extrapyramidal effects, have been reported when some MAOI and phenothiazines are used concomitantly. Although such a reaction has not been reported with promethazine hydrochloride (promethazine hydrochloride injection) , the possibility should be considered.

Laboratory Test Interactions

The following laboratory tests may be affected in patients who are receiving therapy with promethazine hydrochloride (promethazine hydrochloride injection) :

Pregnancy Tests

Diagnostic pregnancy tests based on immunological reactions between HCG and anti-HCG may result in false-negative or false-positive interpretations.

Glucose Tolerance Test

An increase in glucose tolerance has been reported in patients receiving promethazine hydrochloride (promethazine hydrochloride injection) .

This monograph has been modified to include the generic and brand name in many instances.

Last reviewed on RxList: 6/21/2007

Side Effects

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