Action And Clinical Pharmacology: Promethazine is an antihistamine with sedative, antiemetic and antispasmodic properties. In addition, it exerts local anesthetic effects and potentiates analgesics, anesthetics and other CNS depressants.
Indications And Clinical Uses: Allergic reactions: hay fever, urticaria, vasomotor rhinitis, skin allergies, poison ivy, insect bites; for the relief of pruritus due to various dermatologic conditions. Nausea and vomiting of various etiologies: motion sickness, radiation sickness, surgery, anesthesia and gastroenteritis, centrally acting emetics, metabolic or endocrine disorders.
It is also employed as a sedative, hypnotic and tranquilizer in insomnia, nervousness, anxiety, tension; as a local anesthetic for the relief of pruritus and mild burns; as a pre- and postoperative medication in obstetrical analgesia and as a potentiator of anesthetics.
Contra-Indications: Hypersensitivity to phenothiazines, in patients with glaucoma or those in a coma due to CNS depressants.
Promethazine is not recommended for infants below 2 years of age.
Precautions: Promethazine can potentiate CNS depressants such as barbiturates, narcotics, analgesics, and general anesthetics; therefore, dosages of these agents should be reduced when administered concomitantly with promethazine.
Because of its antiemetic properties, promethazine can mask symptoms of intestinal obstruction or intracranial pressure; thus it is necessary to establish the etiology of nausea and vomiting before using high doses of the drug.
Occupational Hazards: Patients should be warned that promethazine may cause drowsiness or dizziness; in such cases, abstain from driving an automobile or operating machinery until this effect has worn off.
The i.m. parenteral route is used most frequently; promethazine should be injected deeply into a large muscle mass.
The i.v. route is well tolerated; however, perivascular extravasation which could be painful should be avoided and speed of injection should not exceed 25 mg/minute; it is preferrable to inject through the tubing of a running infusion set that is known to be functioning satisfactorily.
Children: Use is not recommended in infants up to 2 years of age because of the possible absence or deficiency of detoxifying enzymes and inefficient renal function usually noted in this age group, and also because of its possible effect on sleep pattern.
Adverse Reactions: Promethazine is a phenothiazine derivative. Although the likelihood of those side effects associated with antipsychotic phenothiazines occurring with promethazine seem to be minimal, the possibility exists, especially at higher doses or with prolonged administration.
Adverse reactions with promethazine are those usually seen during antihistamine therapy; they are generally mild and rarely necessitate discontinuation of treatment.
Most frequent side effects are drowsiness and certain anticholinergic effects: dryness of the mouth and more rarely, blurring of vision, dizziness and asthenia.
More rarely, the following effects on the cardiovascular system may be seen, at the beginning of promethazine parenteral therapy mainly: hypotension and tachycardia; occasionally it will be accompanied by nausea and vomiting.
The following have been reported with a rare incidence: paradoxical reactions characterized by hyperexcitability and/or nightmares, especially in children; allergic reactions, including contact dermatitis; photosensitivity; leukopenia.
Symptoms And Treatment Of Overdose: Symptoms: Sedation, respiratory depression, possible convulsions, coma. tag_Treatment
Treatment: No specific antidote. After gastric lavage, treatment is symptomatic. If a pressor agent is necessary, norepinephrine may be used, not epinephrine as it may further depress blood pressure. Centrally acting emetics are ineffective because of the strong antiemetic action of promethazine.
Dosage (dosage expressed in terms of promethazine base – administered as promethazine HCl): The preferred route of administration is by deep i.m. injection.
When administered i.v., the injection rate should not exceed 1 mL (25 mg)/minute. Avoid perivascular extravasation. When possible, injection should be made into the tubing of a running infusion.
Do not administer intra-arterially because of the possibility of severe arteriospasm and resultant gangrene.
Adults: Antihistaminic (H1 receptor): 25 mg; may be repeated within 2 hours if necessary.
Antiemetic: 12.5 to 25 mg every 4 to 6 hours as needed.
Sedative-hypnotic: 25 to 50 mg as needed.
Do not exceed 100 mg daily.
Children (over 2 years of age): Antiemetic: 0.25 to 0.5 mg/kg of body weight i.m. every 4 to 6 hours as needed.
Sedative-hypnotic and premedication: 0.5 to 1 mg/kg of body weight i.m. as needed.
Availability And Storage: Each mL of solution contains: promethazine base 25 mg (as the hydrochloride). Nonmedicinal ingredients: ascorbic acid, potassium metabisulfite, sodium sulfite and water for injection. Ampuls of 2 mL, boxes of 10.
PHENERGANÂ® Injectable RhÃ´ne-Poulenc Rorer Promethazine HCl Antihistamine