Generic Name

Promethazine Hydrochloride

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Classification

FDA Approved Indications

• Nausea and vomiting
• Allergic conditions (rhinitis, conjunctivitis, etc.)
• Preoperative sedation
• Motion sickness

Mechanism of Action

Promethazine exerts its effects primarily by antagonizing histamine H1 receptors, thereby reducing allergic symptoms and nausea. It also has central sedative properties through CNS depression and anticholinergic effects that contribute to its antiemetic action.

Dosage and Administration

Adult: Typically 12.5 to 25 mg every 4 to 6 hours as needed, not to exceed 100 mg per day

Pediatric: For children 2 years and older, 0.25 to 0.5 mg/kg every 4 to 6 hours, not to exceed 25 mg per dose or 75 mg per day

Geriatric: Start at lower doses, closely monitor for CNS and anticholinergic side effects

Renal Impairment: Adjust dosage based on severity, consult specific guidelines

Hepatic Impairment: Use with caution, start at lower doses

Pharmacokinetics

Absorption: Well absorbed from gastrointestinal tract

Distribution: Widely distributed, crosses blood-brain barrier and placenta

Metabolism: Extensively metabolized in the liver

Excretion: Primarily via renal route as metabolites

Half Life: approximately 10-19 hours depending on individual factors

Contraindications

• Coma
• Ex coma state or CNS depression caused by alcohol, hypnotics, opioids, or other CNS depressants
• Children under 2 years old due to risk of respiratory depression

Precautions

• Use with caution in elderly, those with respiratory issues, or with known hypersensitivity to phenothiazines. Risk of neuroleptic malignant syndrome, extrapyramidal symptoms, and severe respiratory depression in children.

Adverse Reactions - Common

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

Adverse Reactions - Serious

• Respiratory depression in children (Rare)
• Extrapyramidal symptoms (Rare)
• Neuroleptic malignant syndrome (Very rare)

Drug-Drug Interactions

• Additive sedation with CNS depressants
• Potential for increased anticholinergic effects when combined with other anticholinergic drugs

Drug-Food Interactions

• Alcohol can increase sedative effects

Drug-Herb Interactions

N/A

Nursing Implications

Patient/Family Teaching

• Avoid alcohol and other CNS depressants.
• Report excessive drowsiness, respiratory difficulty, or allergic reactions.
• Do not operate heavy machinery until effects are known.
• Use caution in elderly due to increased risk of falls or confusion.

Special Considerations

Black Box Warnings:

• Respiratory depression in children under 2 years old, especially with IV use
• Use in pediatric patients under 2 years is contraindicated due to increased risk of respiratory depression.

Genetic Factors: None specifically noted.

Lab Test Interference: Potential false-positive skin test reactions and possible interference with certain diagnostic tests.

Overdose Management

Signs/Symptoms: Extreme sedation, respiratory depression, seizures, hallucinations, coma.

Treatment: Supportive care, airway management, activated charcoal if ingestion was recent, and specific interventions for respiratory or cardiac support as needed.

Storage and Handling

Storage: Store at controlled room temperature, 15-30°C (59-86°F).

Stability: Stable when properly stored, use before expiration date.