Nurses Compass
Drug Guide
Methixene Hydrochloride
Classification
Therapeutic: Antihistamine/Anticholinergic
Pharmacological: Antihistamine, Anticholinergic
FDA Approved Indications
- Allergic conditions such as hay fever, allergic rhinitis, conjunctivitis
Mechanism of Action
Methixene Hydrochloride exhibits anticholinergic and antihistaminic properties, blocking histamine H1 receptors and reducing smooth muscle spasm and capillary permeability associated with allergic responses.
Dosage and Administration
Adult: Typically 10-15 mg two to three times daily, adjusted based on response and tolerability.
Pediatric: Dosage for children should be determined by weight and age; usually starting at 2-5 mg two to three times daily.
Geriatric: Use with caution; start at lower doses due to increased sensitivity and risk of side effects.
Renal Impairment: Adjust dose as needed; no specific guidelines established, monitor closely.
Hepatic Impairment: Use with caution; hepatic metabolism may be impaired, increasing drug levels.
Pharmacokinetics
Absorption: Well absorbed from the gastrointestinal tract.
Distribution: Widely distributed throughout body tissues, crosses the blood-brain barrier.
Metabolism: Primarily metabolized in the liver.
Excretion: Renally excreted, unchanged and as metabolites.
Half Life: Approximately 8-10 hours, but may vary based on individual factors.
Contraindications
- Known hypersensitivity to methixene or other antihistamines.
- Pregnancy and lactation unless benefits outweigh risks.
Precautions
- Use cautiously in patients with glaucoma, urinary retention, or gastrointestinal obstruction; may cause sedation, confusion, or anticholinergic effects.
Adverse Reactions - Common
- Sedation (Common)
- Dry mouth (Common)
- Dizziness (Less common)
Adverse Reactions - Serious
- Acute intraocular pressure increase in glaucoma (Serious)
- Allergic reactions, including rash or hypersensitivity (Rare)
Drug-Drug Interactions
- CNS depressants (enhanced sedation)
- Anticholinergic drugs (additive effects)
Drug-Food Interactions
- Alcohol (potentiates sedative effects)
Drug-Herb Interactions
N/ANursing Implications
Assessment: Monitor for CNS depression, anticholinergic side effects, effectiveness of allergy symptom control.
Diagnoses:
- Risk for sedation or falls in elderly patients.
- Risk for dry mouth and anticholinergic effects.
Implementation: Administer with food if gastrointestinal upset occurs; educate patient about potential drowsiness.
Evaluation: Assess symptom relief and monitor side effects regularly.
Patient/Family Teaching
- Advise against operating heavy machinery until response is known.
- Warn about potential sedation and anticholinergic side effects.
- Instruct to avoid alcohol and other CNS depressants.
- Encourage to report any adverse reactions or signs of allergic response.
Special Considerations
Black Box Warnings:
- None specifically applicable to methixene,
Genetic Factors: Pharmacogenomic variations in metabolism are not well characterized.
Lab Test Interference: May interfere with certain allergy skin testing results.
Overdose Management
Signs/Symptoms: Severe drowsiness, hallucinations, agitation, urinary retention, dry mouth, blurred vision.
Treatment: Supportive care, activated charcoal if ingestion is recent, airway management, and symptomatic treatment. No specific antidote available.
Storage and Handling
Storage: Store at room temperature, away from light and moisture.
Stability: Stable under recommended storage conditions for the duration of the product's shelf life.