Overview
DESCRIPTION Each rectal suppository contains 12.5 mg or 25 mg promethazine HCl with ascorbyl palmitate, cocoa butter, colloidal silicon dioxide, and white wax. Promethazine Hydrochloride Suppositories are for rectal administration only. Promethazine HCl is a racemic compound; the empirical formula is C 17 H 20 N 2 S•HCl and its molecular weight is 320.88.
Mechanism of Action
CLINICAL PHARMACOLOGY Promethazine is a phenothiazine derivative, which differs structurally from the antipsychotic phenothiazines by the presence of a branched side chain and no ring substitution. It is thought that this configuration is responsible for its relative lack (1/10 that of chlorpromazine) of dopamine antagonist properties. Promethazine is an H 1 receptor blocking agent. In addition to its antihistaminic action, it provides clinically useful sedative and antiemetic effects. Promethazine is well absorbed from the gastrointestinal tract. Clinical effects are apparent within 20 minutes after oral administration and generally last four to six hours, although they may persist as long as 12 hours.
Indications
- INDICATIONS AND USAGE Promethazine HCl Suppositories are useful for: Perennial and seasonal allergic rhinitis. Vasomotor rhinitis. Allergic conjunctivitis due to inhalant allergens and foods. Mild, uncomplicated allergic skin manifestations of urticaria and angioedema. Amelioration of allergic reactions to blood or plasma. Dermographism. Anaphylactic reactions, as adjunctive therapy to epinephrine and other standard measures, after the acute manifestations have been controlled. Preoperative, postoperative, or obstetric sedation.
Common Doses
- 25 mg
- 12.5 mg
- 0.5 mg
- 50 mg
Dosage
DOSAGE AND ADMINISTRATION Promethazine HCl Suppositories are contraindicated for children under 2 years of age (see WARNINGS - Black Box Warning and Use in Pediatric Patients ). Promethazine HCl Suppositories are for rectal administration only. Allergy - The average dose is 25 mg taken before retiring; however, 12.5 mg may be taken before meals and on retiring, if necessary. Single 25 mg doses at bedtime or 6.25 to 12.5 mg taken three times daily will usually suffice.
Black Box Warning
PROMETHAZINE HCl SUPPOSITORIES SHOULD NOT BE USED IN PEDIATRIC PATIENTS LESS THAN 2 YEARS OF AGE BECAUSE OF THE POTENTIAL FOR FATAL RESPIRATORY DEPRESSION. POSTMARKETING CASES OF RESPIRATORY DEPRESSION, INCLUDING FATALITIES, HAVE BEEN REPORTED WITH USE OF PROMETHAZINE HCl SUPPOSITORIES IN PEDIATRIC PATIENTS LESS THAN 2 YEARS OF AGE. A WIDE RANGE OF WEIGHT-BASED DOSES OF PROMETHAZINE HCl SUPPOSITORIES HAVE RESULTED IN RESPIRATORY DEPRESSION IN THESE PATIENTS. CAUTION SHOULD BE EXERCISED WHEN ADMINISTERING PROMETHAZINE HCl TO PEDIATRIC PATIENTS 2 YEARS OF AGE AND OLDER.
Contraindications
- CONTRAINDICATIONS Promethazine HCl Suppositories are contraindicated for use in pediatric patients less than two years of age. Promethazine HCl Suppositories are contraindicated in comatose states, and in individuals known to be hypersensitive or to have had an idiosyncratic reaction to promethazine or to other phenothiazines. Antihistamines are contraindicated for use in the treatment of lower respiratory tract symptoms including asthma.
Side Effects
- ADVERSE REACTIONS Central Nervous System - Drowsiness is the most prominent CNS effect of this drug. Sedation, somnolence, blurred vision, dizziness; confusion, disorientation, and extrapyramidal symptoms such as oculogyric crisis, torticollis, and tongue protrusion; lassitude, tinnitus, incoordination, fatigue, euphoria, nervousness, diplopia, insomnia, tremors, convulsive seizures, excitation, catatonic-like states, hysteria and hallucinations have also been reported. Cardiovascular - Increased or decreased blood pressure, tachycardia, bradycardia, faintness.
Interactions
- Drug Interactions CNS Depressants - Promethazine HCl Suppositories may increase, prolong, or intensify the sedative action of other central-nervous-system depressants, such as alcohol, sedatives/hypnotics (including barbiturates), narcotics, narcotic analgesics, general anesthetics, tricyclic antidepressants, and tranquilizers; therefore, such agents should be avoided or administered in reduced dosage to patients receiving promethazine HCl.