Promethazine has adverse effects similar to those of other antihistamines and shares the toxic potentials of the phenothiazines; the usual precautions of antihistamine and phenothiazine therapy should be observed. and also Although the risk of adverse reactions (e.g., blood dyscrasias, hepatotoxicity, reactivation of psychotic processes, tachycardia, cardiac arrest, endocrine disturbances, dermatologic disorders, ocular changes, hypersensitivity reactions) that have occurred during long-term administration of antipsychotic phenothiazines appears to be minimal, the possibility that they could occur with prolonged administration of promethazine should be considered.
The most common adverse reactions of promethazine are pronounced sedative effects and confusion or disorientation. Adverse anticholinergic effects of the drug include dryness of mouth, blurring of vision, and, rarely, dizziness. Extrapyramidal reactions may occur with high doses and usually subside with dosage reduction. Lassitude, fatigue, incoordination, tinnitus, diplopia, oculogyric crises, insomnia, excitation, nervousness, euphoria, hysteria, tremors, abnormal movements, nightmares, delirium, agitation, seizures, hallucinations, torticollis, tongue protrusion, oversedation, dystonic reactions, and catatonic-like states have been reported. Restlessness, akathisia, and, occasionally, marked irregular respiration have occurred. Neuroleptic malignant syndrome (NMS) also may occur. Patients with pain who have received inadequate or no analgesia have developed athetoid-like movements of the upper extremities following parenteral administration of promethazine. These symptoms usually disappeared when the pain was controlled.
Leukopenia, thrombocytopenia, thrombocytopenic purpura, and agranulocytosis have been reported in patients receiving promethazine.
Tachycardia, bradycardia, increased or decreased blood pressure, and faintness have occurred in patients receiving promethazine. Although rapid IV administration of promethazine may produce a transient fall in blood pressure, blood pressure usually is maintained or slightly elevated when the drug is given slowly. Venous thrombosis at the injection site also has been reported.
Promethazine has been associated with obstructive jaundice, which was usually reversible following discontinuance of the drug. Cholestatic jaundice, nausea, and vomiting have been reported in patients receiving promethazine. Photosensitivity has been reported and may be a contraindication to further promethazine therapy. Urticaria, dermatitis, angioedema, dermatologic reactions, and asthma also have been reported. Nasal stuffiness, respiratory depression (may be fatal), cardiac arrest, and apnea (may be fatal) also may occur.
Local Reactions Associated with Promethazine Hydrochloride Injection
Severe chemical irritation and damage to tissues (e.g., burning, pain, erythema, swelling, severe spasm of distal vessels, thrombophlebitis, venous thrombosis, phlebitis, abscesses, tissue necrosis, gangrene) may occur with administration of promethazine injection, regardless of the route of administration. Such irritation and damage also may result from perivascular extravasation, unintentional intra-arterial injection, and intraneuronal or perineuronal infiltration. Parenteral administration of promethazine may produce nerve damage (ranging from temporary sensory loss to palsies and paralysis) while injection near or into a nerve may result in permanent tissue damage. In some cases, surgical intervention (e.g., fasciotomy, skin graft, amputation) may be needed.