Home Drug Guide Promethazine Hydrochloride; Dextromethorphan Hydrobromide

Drug Guide

Generic Name

Promethazine Hydrochloride; Dextromethorphan Hydrobromide

Brand Names Phenergan DM, Cough & Cold formulations containing dextromethorphan and promethazine

Classification

Therapeutic: Antitussive and Antihistamine

Pharmacological: Phenothiazine antihistamine and cough suppressant

FDA Approved Indications

Relief of cough and upper respiratory symptoms associated with allergies or cold
Nausea and vomiting (for promethazine)

Mechanism of Action

Promethazine acts as an antihistamine with sedative properties, blocking H1 histamine receptors. Dextromethorphan acts centrally on the cough center in the medulla to suppress cough reflex.

Dosage and Administration

Adult: Dose varies depending on formulation; typically, promethazine 12.5-25 mg every 4-6 hours, dextromethorphan 10-20 mg every 4 hours as needed.

Pediatric: Use with caution; consult specific product dosing instructions, generally not recommended under 2 years for promethazine due to respiratory risks.

Geriatric: Lower initial doses may be appropriate due to increased sensitivity, monitor for CNS effects.

Renal Impairment: Adjust doses cautiously; consult specific guidelines.

Hepatic Impairment: Use with caution; dose adjustments may be necessary.

Pharmacokinetics

Absorption: Well absorbed orally.

Distribution: Widely distributed including crossing the blood-brain barrier.

Metabolism: Primarily hepatic via CYP450 enzymes.

Excretion: Renal and biliary; metabolites excreted in urine and feces.

Half Life: Promethazine approximately 10-19 hours; Dextromethorphan about 2-4 hours.

Contraindications

Children under 2 years (promethazine) due to respiratory risk.
Known hypersensitivity to phenothiazines or dextromethorphan.

Precautions

Use with caution in elderly, during pregnancy, breastfeeding, or in patients with respiratory depression, glaucoma, prostatic hypertrophy, or history of seizures.

Adverse Reactions - Common

Drowsiness (Common)
Dizziness (Common)
Dry mouth (Common)

Adverse Reactions - Serious

Respiratory depression (dextromethorphan) (Uncommon)
Extrapyramidal symptoms (promethazine) (Rare)
Seizures (dextromethorphan) (Rare)
Allergic reactions (Rare)

Drug-Drug Interactions

CNS depressants (increase sedation)
Monoamine oxidase inhibitors (risk of serotonin syndrome for dextromethorphan)

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Assessment: Assess cough severity, respiratory status, sedation level, allergy history.

Diagnoses:

Risk for sedation or respiratory depression.
Impaired comfort related to cough or nausea.

Implementation: Administer after meals to minimize gastrointestinal upset, monitor respiratory status, watch for excessive sedation.

Evaluation: Effectiveness in suppressing cough and alleviating nausea, monitor for adverse effects.

Patient/Family Teaching

Advise against operating machinery or driving due to sedation.
Warn about potential drowsiness, dizziness.
Avoid alcohol and other CNS depressants.
Instruct on proper dosing and timing.

Special Considerations

Black Box Warnings:

Promethazine has black box warning for respiratory depression in children under 2 years.
Dextromethorphan abuse potential.

Genetic Factors: Variability in metabolism via CYP2D6 affecting dextromethorphan levels.

Lab Test Interference: N/A

Overdose Management

Signs/Symptoms: Sedation, respiratory depression, hallucinations, agitation.

Treatment: Supportive care, airway management, activated charcoal if early, naloxone for respiratory depression if opioid overdose suspected, as appropriate.

Storage and Handling

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

Stability: Stable under proper storage conditions.