PROMETHAZINE HYDROCHLORIDE- promethazine hydrochloride tablet
Promethazine hydrochloride, a phenothiazine derivative, is designated chemically as 10- [2-(Dimethylamino)propyl]phenothiazine monohydrochloride and has the following structural formula:
Promethazine hydrochloride is a racemic compound; the empirical formula is C 17 H 20 N 2 S HCl and its molecular weight is 320.88.
Promethazine hydrochloride occurs as a white to faint yellow, practically odorless, crystalline powder which slowly oxidizes and turns blue on prolonged exposure to air. It is freely soluble in water and soluble in alcohol.
Each tablet for oral administration contains 12.5 mg, 25 mg or 50 mg promethazine hydrochloride, USP. The inactive ingredients include: lactose anhydrous, magnesium stearate, and microcrystalline cellulose. The 50 mg also contains D&C Red # 27 Lake.
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 H1 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. Promethazine is metabolized by the liver to a variety of compounds; the sulfoxides of promethazine and N-demethylpromethazine are the predominant metabolites appearing in the urine.
Promethazine Hydrochloride Tablets are useful for:
Perennial and seasonal allergic 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.
Anaphylactic reactions as adjunctive therapy to epinephrine and other standard measures after the acute manifestations have been controlled.
Preoperative, postoperative and obstetric sedation.
Prevention and control of nausea and vomiting associated with certain types of anesthesia and surgery.
Therapy adjunctive to meperidine or other analgesics for control of postoperative pain.
Sedation in both children and adults as well as relief of apprehension and production of light sleep from which the patient can be easily aroused.
Active and prophylactic treatment of motion sickness. Antiemetic therapy in postoperative patients.
Promethazine Hydrochloride Tablets, USP are contraindicated for use in pediatric patients less than two years of age.
Promethazine is contraindicated in comatose state, and in individuals known to be hypersensitive or to have had an idiosyncratic reaction to promethazine or to other phenthiazines.
Antihistamines are contraindicated for use in the treatment of lower respiratory tract symptoms including asthma.
Promethazine hydrochloride 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 hydrochloride in pediatric patients less than 2 years of age. A wide range of weight-based doses of promethazine hydrochloride have resulted in respiratory depression in these patients.Caution should be exercised when administering promethazine hydrochloride to pediatric patients 2 years of age and older. It is recommended that the lowest effective dose of promethazine hydrochloride be used in pediatric patients 2 years of age and older and concomitant administration of other drugs with respiratory depressant effects be avoided.
CNS Depression: Promethazine Hydrochloride Tablets may impair the mental and/or physical abilities required for the performance of potentially hazardous tasks, such as driving a vehicle or operating machinery. The impairment may be amplified by concomitant use 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 either be eliminated or given in reduced dosage in the presence of promethazine hydrochloride (see PRECAUTIONS, Information for Patients and Drug Interactions).
Respiratory Depression: Promethazine Hydrochloride Tablets, USP may lead to potentially fatal respiratory depression.
Use of Promethazine Hydrochloride Tablets, USP in patients with compromised respiratory function (e.g., COPD, sleep apnea) should be avoided.
Lower Seizure Threshold: Promethazine Hydrochloride Tablets, USP may lower seizure threshold. It should be used with caution in persons with seizure disorders or in persons who are using concomitant medications, such as narcotics or local anesthetics, which may also affect seizure threshold. Bone-Marrow Depression: Promethazine Hydrochloride Tablets, should be used with caution in patients with bone marrow depression. Leukopenia and agranulocytosis has been reported, usually when promethazine hydrochloride has been used in association with other known marrow-toxic agents.
Neuroleptic Malignant Syndrome: A potentially fatal symptom complex sometimes referred to as Neuroleptic Malignant Syndrome (NMS) has been reported in association with promethazine hydrochloride alone or in combination with antipsychotic drugs. Clinical manifestations of NMS are hyperpyrexia, muscle rigidity, altered mental status and evidence of autonomic instability (irregular pulse or blood pressure, tachycardia, diaphoresis and cardiac dysrhythmias).
The diagnostic evaluation of patients with this syndrome is complicated. In arriving at a diagnosis, it is important to identify cases where the clinical presentation includes both serious medical illness (e.g., pneumonia, systemic infection, etc.) and untreated or inadequately treated extrapyramidal signs and symptoms (EPS). Other important consideration in the differential diagnosis include central anticholinergic toxicity, heat stroke, drug fever and primary central nervous system (CNS) pathology.
The management of NMS should include 1) immediate discontinuation of promethazine hydrochloride, antipsychotic drugs, if any, and other drugs not essential to concurrent therapy, 2) intensive symptomatic treatment and medical monitoring, and 3) treatment of any concomitant serious medical problems for which specific treatments are available. There is no general agreement about specific pharmacological treatment regimens for uncomplicated NMS.
Since reoccurrences of NMS have been reported with phenothiazines, the reintroduction of promethazine hydrochloride should be carefully considered.
Use in Pediatric Patients: Promethazine Hydrochloride Tablets, USP are contraindicated for use in pediatric patients less than two years of age.
Caution should be exercised when administering Promethazine Hydrochloride Tablets, USP to pediatric patients 2 years of age and older because of the potential for fatal respiratory depression. Respiratory depression and apnea, sometimes associated with death, are strongly associated with promethazine products and are not directly related to individualized weight-based dosing, which might otherwise permit safe administration. Concomitant administration of promethazine products with other respiratory depressants has an association with respiratory depression, and sometimes death, in pediatric patients.
Antiemetics are not recommended for treatment of uncomplicated vomiting in pediatric patients, and their use should be limited to prolonged vomiting of known etiology. The extrapyramidal symptoms which can occur secondary to Promethazine Hydrochloride Tablets administration may be confused with the CNS signs of undiagnosed primary disease, e.g., encephalopathy or Reye’s syndrome. The use of Promethazine Hydrochloride Tablets should be avoided in pediatric patients whose signs and symptoms may suggest Reye’s syndrome or other hepatic diseases.
Excessively large dosages of antihistamines, including Promethazine Hydrochloride Tablets in pediatric patients may cause sudden death (see OVERDOSAGE). Hallucinations and convulsions have occurred with therapeutic doses and overdoses of promethazine hydrochloride in pediatric patients. In pediatric patients who are acutely ill associated with dehydration, there is an increased susceptibility to dystonias with the use of promethazine hydrochloride.
Other Considerations: Administration of promethazine hydrochloride has been associated with reported cholestatic jaundice.
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