zine 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 hcl (see precautions-information for patients and drug interactions ). respiratory depression promethazine may lead to potentially fatal respiratory depression. use of promethazine in patients with compromised respiratory function (e.g., copd, sleep apnea) should be avoided. lower seizure threshold promethazine 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 should be used with caution in patients with bone-marrow depression. leukopenia and agranulocytosis have been reported, usually when promethazine hcl 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 hcl 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 considerations 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 hcl, 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 recurrences of nms have been reported with phenothiazines, the reintroduction of promethazine hcl should be carefully considered. use in pediatric patients promethazine products are contraindicated for use in pediatric patients less than two years of age. caution should be exercised when administering promethazine products 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 administration may be confused with the cns signs of undiagnosed primary disease, e.g., encephalopathy or reye’s syndrome. the use of promethazine products 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, 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 hcl. other consideration: administration of promethazine has been associated with reported cholestatic jaundice.

ars to under 6 years ¼ to ½ teaspoonful (1.25 to 2.5 ml) every 4 to 6 hours, not to exceed 10 ml in 24 hours.

pnea (potentially fatal) (see warnings-promethazine; respiratory depression ) . other - angioneurotic edema. neuroleptic malignant syndrome (potentially fatal) has also been reported (see warnings-promethazine; neuroleptic malignant syndrome ). paradoxical reactions - hyperexcitability and abnormal movements have been reported in patients following a single administration of promethazine hcl. consideration should be given to the discontinuation of promethazine hcl and to the use of other drugs if these reactions occur. respiratory depression, nightmares, delirium, and agitated behavior have also been reported in some of these patients.

e 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. 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.