Nurses Compass
Drug Guide
Methdilazine Hydrochloride
Classification
Therapeutic: Antihistamine, Antiemetic
Pharmacological: Phenothiazine derivative
FDA Approved Indications
- Prevention and treatment of nausea and vomiting associated with surgery, anesthesia, or other conditions
Mechanism of Action
Methdilazine works by blocking histamine H1 receptors, as well as possessing anticholinergic properties, which contribute to its antiemetic effects.
Dosage and Administration
Adult: 25-50 mg every 4-6 hours as needed, not to exceed 300 mg/day
Pediatric: Use under medical supervision; dosing varies by age and condition
Geriatric: Start at lower doses due to increased sensitivity; monitor closely for side effects
Renal Impairment: Adjust dosage based on severity of impairment; consult specific guidelines
Hepatic Impairment: Use with caution; consider dose reduction and close monitoring
Pharmacokinetics
Absorption: Well absorbed orally
Distribution: Widely distributed; crosses the blood-brain barrier
Metabolism: Extensively metabolized in the liver
Excretion: Primarily in urine, some in feces
Half Life: Approximately 10 hours
Contraindications
- Known hypersensitivity to methdilazine or phenothiazines
- Comorbid conditions where anticholinergic effects could be harmful (e.g., glaucoma, urinary retention)
Precautions
- Use with caution in patients with cardiovascular disease, hepatic or renal impairment, prostate hypertrophy, seizure disorders, or electrolyte imbalances
Adverse Reactions - Common
- Drowsiness or sedation (Frequent)
- Dry mouth (Common)
- Dizziness (Common)
Adverse Reactions - Serious
- Extrapyramidal symptoms (Uncommon)
- QT prolongation leading to arrhythmias (Rare)
- Hypotension (Uncommon)
- Allergic reactions including rash, pruritus (Rare)
Drug-Drug Interactions
- Other CNS depressants (additive sedation)
- Anticholinergics (potentiation of anticholinergic side effects)
- QT-prolonging agents (risk of arrhythmias)
Drug-Food Interactions
N/ADrug-Herb Interactions
N/ANursing Implications
Assessment: Monitor for effectiveness in controlling nausea, sedation level, and potential side effects such as dry mouth, urinary retention, or extrapyramidal symptoms
Diagnoses:
- Risk for falls related to sedation or dizziness
- Risk for injury related to extrapyramidal symptoms
Implementation: Administer as prescribed, preferably with food to reduce gastrointestinal upset; monitor vital signs and cardiac status in at-risk patients
Evaluation: Assess relief of nausea, monitor for adverse effects, and adjust dose accordingly
Patient/Family Teaching
- Take medication exactly as prescribed
- Report any signs of allergic reaction, severe side effects, or unusual movements
- Avoid activities requiring mental alertness until drug effects are known
- Inform healthcare provider about all other medications being taken
Special Considerations
Black Box Warnings:
- None specifically for methdilazine, but caution advised for QT prolongation
Genetic Factors: None well established
Lab Test Interference: May affect cardiac conduction studies or electrolyte panels
Overdose Management
Signs/Symptoms: Drowsiness, agitation, CNS depression, hallucinations, seizures, hypotension, arrhythmias
Treatment: Supportive care, activated charcoal if ingestion was recent, maintain airway and ventilation, monitor cardiac function, administer IV fluids, and consider use of saline or sodium bicarbonate for specific arrhythmias
Storage and Handling
Storage: Store in a cool, dry, well-ventilated place away from light and moisture
Stability: Stable when stored properly, check expiration date prior to use