Drug Guide
Darifenacin Hydrobromide
Classification
Therapeutic: Urinary Antispasmodic
Pharmacological: Muscarinic Receptor Antagonist
FDA Approved Indications
- Overactive Bladder with Symptoms of Urgency, Urinary Frequency, and Urgency incontinence
Mechanism of Action
Darifenacin selectively antagonizes M3 muscarinic receptors in the bladder detrusor muscle, reducing involuntary contractions and increasing bladder capacity.
Dosage and Administration
Adult: Starting dose is 15 mg once daily. Dose may be increased to 15 mg twice daily based on efficacy and tolerability.
Pediatric: Not approved for pediatric use.
Geriatric: Use with caution; consider lower starting doses due to potential increased sensitivity.
Renal Impairment: Adjust dose based on severity; typically, no adjustment for mild impairment, but caution advised in moderate to severe impairment.
Hepatic Impairment: Use with caution; dose adjustment may be necessary.
Pharmacokinetics
Absorption: Well absorbed orally, with peak plasma concentrations in approximately 3-4 hours.
Distribution: Extensively distributed; volume of distribution approximately 245 L.
Metabolism: Primarily metabolized in the liver via CYP3A4 and CYP2D6 pathways.
Excretion: Excreted mainly in feces (about 70%), with the remainder in urine.
Half Life: Approximately 13-19 hours.
Contraindications
- Urinary retention
- Gastric retention
- Uncontrolled narrow-angle glaucoma
Precautions
- Use with caution in patients with hepatic impairment, urinary retention, gastric retention, or gastrointestinal incontinence.
- Monitor for signs of anticholinergic side effects.
Adverse Reactions - Common
- Dry mouth (Common)
- Constipation (Common)
- blurred vision (Less common)
Adverse Reactions - Serious
- Urinary retention (Rare)
- Allergic reactions (rash, angioedema) (Rare)
- QT prolongation (Rare)
Drug-Drug Interactions
- Other anticholinergic drugs (increased anticholinergic effects)
- CYP3A4 inhibitors (e.g., ketoconazole, clarithromycin) may increase darifenacin levels
Drug-Food Interactions
- None specifically identified
Drug-Herb Interactions
- None specifically identified
Nursing Implications
Assessment: Monitor for signs of urinary retention, dry mouth, constipation, and visual disturbances.
Diagnoses:
- Risk for urinary retention
- Risk for constipation
- Impaired skin integrity (dry mouth)
Implementation: Administer with food to minimize gastrointestinal irritation. Monitor renal and hepatic function during long-term therapy.
Evaluation: Assess the efficacy in reducing urinary urgency and frequency. Monitor for adverse effects.
Patient/Family Teaching
- Take medication exactly as prescribed.
- Report any signs of urinary retention, severe dry mouth, or vision changes.
- Avoid activities requiring alertness until response is known.
- Maintain adequate fluid intake and dietary fiber to prevent constipation.
Special Considerations
Black Box Warnings:
- None identified currently.
Genetic Factors: Genetic variations in CYP2D6 and CYP3A4 enzymes can influence drug metabolism and response.
Lab Test Interference: None known.
Overdose Management
Signs/Symptoms: Severe anticholinergic effects such as hallucinations, mydriasis, tachycardia, agitation, dry skin, and dry mouth.
Treatment: Supportive care; activated charcoal may be used if overdose is recent; physostigmine may be considered in severe cases under medical supervision.
Storage and Handling
Storage: Store at room temperature between 20°C and 25°C (68°F and 77°F).
Stability: Stable under recommended storage conditions.