Home Drug Guide Dextromethorphan Hydrobromide and Promethazine Hydrochloride

Drug Guide

Generic Name

Dextromethorphan Hydrobromide and Promethazine Hydrochloride

Brand Names Promethazine DM, Prometh W/ Dextromethorphan, Promethazine W/ Dextromethorphan, Pherazine DM

Classification

Therapeutic: Cough suppressant and Antiemetic

Pharmacological: Antitussive and Phenothiazine antipsychotic

FDA Approved Indications

Relief of cough due to minor throat and bronchial irritation
Prevention and control of nausea and vomiting

Mechanism of Action

Dextromethorphan suppresses the cough reflex by acting on cough center in the brain (medulla). Promethazine blocks H1 histamine receptors and has sedative effects; it also has anticholinergic properties that contribute to its antiemetic action.

Dosage and Administration

Adult: Dosage varies; typically 10-20 mg every 4-6 hours as needed, not to exceed 120 mg per day.

Pediatric: Dosage based on weight and age, consult specific product labeling.

Geriatric: Use with caution; start at lower end of dosing range due to increased sensitivity.

Renal Impairment: Adjust dosage accordingly, reduced clearance in renal impairment.

Hepatic Impairment: Use with caution; possible dose reduction needed.

Pharmacokinetics

Absorption: Rapid absorption from GI tract.

Distribution: Widely distributed; crosses blood-brain barrier.

Metabolism: Primarily hepatic via CYP2D6; extensive first-pass metabolism.

Excretion: Renal and fecal routes.

Half Life: Dextromethorphan: approximately 2-4 hours; Promethazine: approximately 10-14 hours.

Contraindications

Hypersensitivity to components
Children under 2 years due to risk of respiratory depression
Prolonged QT interval or recent MI

Precautions

Use with caution in patients with respiratory depression, asthma, liver impairment, or urinary retention. Avoid concurrent use with other CNS depressants.

Adverse Reactions - Common

Drowsiness, dizziness (Common)
Dry mouth, blurred vision (Common)

Adverse Reactions - Serious

Respiratory depression (Rare)
Seizures (with overdose) (Very rare)
Extrapyramidal symptoms (Rare)
QT prolongation and arrhythmias (Rare)

Drug-Drug Interactions

Other CNS depressants, alcohol, MAO inhibitors, QT-prolonging agents

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Assessment: Monitor respiratory status, level of consciousness, and extrapyramidal symptoms.

Diagnoses:

Risk of respiratory depression
Impaired comfort related to dry mouth or sedation

Implementation: Administer with food or milk to reduce GI upset, monitor for adverse effects.

Evaluation: Assess effectiveness in controlling cough and nausea/vomiting, monitor for side effects.

Patient/Family Teaching

Do not operate heavy machinery or drive until response is known.
Avoid alcohol and other CNS depressants.
Report excessive drowsiness, respiratory difficulty, or new symptoms promptly.

Special Considerations

Black Box Warnings:

Respiratory depression in children under 2 years, contraindicated in this age group.
Potential for respiratory depression with overdose.

Genetic Factors: CYP2D6 metabolizer status can affect drug levels.

Lab Test Interference: None noted.

Overdose Management

Signs/Symptoms: Drowsiness, hallucinations, agitation, respiratory depression, seizures.

Treatment: Supportive care, airway management, activated charcoal if ingestion is recent, and possible use of opioid antagonists or other specific therapies as needed.

Storage and Handling

Storage: Store at room temperature, away from light and moisture.

Stability: Stable under proper storage conditions for the duration specified by the manufacturer.