PHENYLEPHRINE Drug Interactions: What You Need to Know

Drug Interactions Promethazine CNS Depressants Promethazine 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. When given concomitantly with promethazine, the dose of barbiturates should be reduced by at least one-half, and the dose of narcotics should be reduced by one-quarter to one-half. Dosage must be individualized. Excessive amounts of promethazine HCl relative to a narcotic may lead to restlessness and motor hyperactivity in the patient with pain; these symptoms usually disappear with adequate control of the pain.

Epinephrine

Because of the potential for promethazine to reverse epinephrine's vasopressor effect, epinephrine should NOT be used to treat hypotension associated with promethazine overdose.

Anticholinergics

Concomitant use of other agents with anticholinergic properties should be undertaken with caution.

Monoamine Oxidase

Inhibitors (MAOI) Drug interactions, including an increased incidence of extrapyramidal effects, have been reported when some MAOI and phenothiazines are used concomitantly.

Phenylephrine Drug

Phenylephrine with prior administration of monoamine oxidase inhibitors (MAOI).

Effect

Cardiac pressor response potentiated. May cause acute hypertensive crisis.

Drug

Phenylephrine with tricyclic antidepressants.

Effect

Pressor response increased.

Drug

Phenylephrine with ergot alkaloids.

Effect

Excessive rise in blood pressure.

Drug

Phenylephrine with bronchodilator sympathomimetic agents and with epinephrine or other sympathomimetics.

Effect

Tachycardia or other arrhythmias may occur.

Drug

Phenylephrine with atropine sulfate.

Effect

Reflex bradycardia blocked; pressor response enhanced.

Drug

Phenylephrine with prior administration of propranolol or other β-adrenergic blockers.

Effect

Cardiostimulating effects blocked.

Drug

Phenylephrine with prior administration of phentolamine or other α-adrenergic blockers.

Effect

Pressor response decreased.

Drug

Phenylephrine with diet preparations, such as amphetamines or phenylpropanolamine.

Effect

Synergistic adrenergic response.

The 10% strength is contraindicated in:

• Patients with hypertension, or thyrotoxicosis (4.1)
• Pediatric patients less than 1 year of age due to increased risk of systemic toxicity (4.2)

4.1 Cardiac and Endocrine Disease Phenylephrine hydrochloride ophthalmic solution 10% is contraindicated in patients with hypertension or thyrotoxicosis. Phenylephrine hydrochloride ophthalmic solution 2.5% should be used in these patients.

4.2 Pediatric Patients Less Than 1 Year of Age Phenylephrine hydrochloride ophthalmic solution 10% is contraindicated in pediatric patients less than 1 year of age due to the increased risk of systemic toxicity. Phenylephrine hydrochloride ophthalmic solution 2.5% should be used in these patients [See Dosage and Administration (2.2) ] .

4.1 Cardiac and Endocrine Disease Phenylephrine hydrochloride ophthalmic solution 10% is contraindicated in patients with hypertension or thyrotoxicosis. Phenylephrine hydrochloride ophthalmic solution 2.5% should be used in these patients.

4.2 Pediatric Patients Less Than 1 Year of Age Phenylephrine hydrochloride ophthalmic solution 10% is contraindicated in pediatric patients less than 1 year of age due to the increased risk of systemic toxicity. Phenylephrine hydrochloride ophthalmic solution 2.5% should be used in these patients [See Dosage and Administration (2.2) ] .

WARNINGS 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 results 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.

Sulfite

Sensitivity: Promethazine Hydrochloride and Phenylephrine Hydrochloride Oral Solution contains sodium metabisulfite, a sulfite that may cause allergic-type reactions including anaphylactic symptoms and life-threatening or less severe asthmatic episodes in certain susceptible people. The overall prevalence of sulfite sensitivity in the general population is unknown and probably low. Sulfite sensitivity is seen more frequently in asthmatic than in nonasthmatic people. Promethazine: CNS Depression- Promethazine 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, sometime 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 Considerations

Administration of promethazine has been associated with reported cholestatic jaundice. Phenylephrine: Because phenylephrine is an adrenergic agent, it should be given with caution to patients with thyroid diseases, diabetes mellitus, and heart disease or those receiving tricyclic antidepressants. Men with symptomatic, benign prostatic hypertrophy can experience urinary retention when given oral nasal decongestants. Phenylephrine can cause a decrease in cardiac output, and extreme caution should be used when administering the drug parenterally or orally to patients with arteriosclerosis, to elderly individuals, and/or to patients with initially poor cerebral or coronary circulation. Phenylephrine should be used with caution in patients taking diet preparations, such as amphetamines or phenylpropanolamine, because synergistic adrenergic effects could result in serious hypertensive response and possible stroke.