Drug Guide
Phenylephrine Hydrochloride and Promethazine Hydrochloride
Classification
Therapeutic: Decongestant and Antihistamine
Pharmacological: Sympathomimetic and Antihistaminic
FDA Approved Indications
- Relief of allergy symptoms, such as hay fever, allergic conjunctivitis, and allergic rhinitis
- Relief of cold symptoms, including nasal congestion and cough associated with upper respiratory allergies
Mechanism of Action
Phenylephrine stimulates alpha-adrenergic receptors causing vasoconstriction, leading to reduced nasal congestion. Promethazine blocks histamine H1 receptors, reducing allergy symptoms. The combination provides relief from nasal congestion and allergy symptoms.
Dosage and Administration
Adult: Dose varies; typically 1-2 tablets every 4-6 hours, not exceeding 8 doses in 24 hours.
Pediatric: Use is generally cautionary; consult specific product guidelines based on age and weight.
Geriatric: Adjust dose if necessary; monitor for cardiovascular effects.
Renal Impairment: Use with caution; dose adjustments may be needed.
Hepatic Impairment: Use with caution; monitor for increased sedation.
Pharmacokinetics
Absorption: Rapid oral absorption.
Distribution: Widely distributed; crosses blood-brain barrier.
Metabolism: Metabolized in the liver.
Excretion: Excreted mainly in urine.
Half Life: Phenylephrine: approx. 2.5 hours; Promethazine: approx. 10-19 hours.
Contraindications
- Hypersensitivity to phenylephrine or promethazine.
- Severe hypertension or cardiovascular disease (phenylephrine).
- Asthma or airway obstruction (promethazine).
Precautions
- Use cautiously in patients with prostate hypertrophy, glaucoma, or seizure disorders.
- Caution in elderly due to risk of sedation and confusion.
- Potential for precipitating hypertensive crisis in patients on MAOIs.
Adverse Reactions - Common
- Drowsiness, dizziness (Common)
- Nervousness, insomnia (Common)
- Dry mouth, blurred vision (Common)
Adverse Reactions - Serious
- Respiratory depression (rare) (Serious)
- Hypotension or hypertension (phenylephrine) (Serious)
- Extrapyramidal symptoms, severe allergic reactions (Rare)
Drug-Drug Interactions
- Monoamine oxidase inhibitors (MAOIs) – risk of hypertensive crisis
- Other CNS depressants – increased sedation
- Blood pressure medications – altered effectiveness
Drug-Food Interactions
- Avoid excessive caffeine, which may counteract sedative effects.
Drug-Herb Interactions
N/ANursing Implications
Assessment: Monitor blood pressure, cardiovascular status, and CNS status.
Diagnoses:
- Risk for hypertension or hypotension
- Risk for CNS depression or agitation
Implementation: Administer with food or milk if gastrointestinal upset occurs. Educate about potential sedation.
Evaluation: Assess relief of allergy and cold symptoms, monitor for side effects.
Patient/Family Teaching
- Advise against operating heavy machinery due to drowsiness.
- Instruct not to exceed recommended dose.
- Warn about potential interactions with other medications and alcohol.
- Advise about the possibility of dizziness; caution against sudden position changes.
Special Considerations
Black Box Warnings:
- Potential for respiratory depression with promethazine, especially in children under 2 years.
- Phenylephrine should be used cautiously in patients with cardiovascular disease.
Genetic Factors: Genetic variability may affect metabolism and response.
Lab Test Interference: May affect blood pressure monitoring readings.
Overdose Management
Signs/Symptoms: Severe drowsiness, seizures, cardiovascular instability, respiratory depression.
Treatment: Supportive care; maintain airway, monitor vital signs, activated charcoal if within appropriate time frame, and symptomatic treatment.
Storage and Handling
Storage: Store at room temperature, away from light and moisture.
Stability: Stable under recommended storage conditions.