darifenacin

(dar-i-fen-a-sin) darifenacin,

Enablex

(trade name)

Classification

Therapeutic: urinary tract antispasmodics
Pharmacologic: anticholinergics
Pregnancy Category: C

Indications

Overactive bladder with symptoms (urge incontinence, urgency, frequency).

Action

Acts as a muscarinic (cholinergic) receptor antagonist; antagonizes bladder smooth muscle contraction.

Therapeutic effects

Decreased symptoms of overactive bladder.

Pharmacokinetics

Absorption: 15–19% absorbed.Distribution: Unknown.Protein Binding: 98%.Metabolism and Excretion: Extensively metabolized by the CYP2D6 enzyme system in most individuals; genetic implication poor metabolizers (7% of Caucasians, 2% of African Americans) have less CYP2D6 activity with less metabolism occurring. Some metabolism via CYP3A4 enzyme system. 60% excreted renally as metabolites, 40% in feces as metabolites.Half-life: 13–19 hr.

Time/action profile

ROUTE	ONSET	PEAK	DURATION
PO	unknown	7 hr	24 hr

Contraindications/Precautions

Contraindicated in: Hypersensitivity;Urinary retention;Gastric retention;Uncontrolled angle-closure glaucoma;Severe hepatic impairment.Use Cautiously in: Concurrent use of CYP3A4 inhibitors (use lower dose/clinical monitoring may be necessary);Moderate hepatic impairment (lower dose recommended);Bladder outflow obstruction;GI obstructive disorders, ↓ GI motility, severe constipation or ulcerative colitis;Myasthenia gravis;Angle-closure glaucoma; Lactation / Pediatric: Safety not established; Obstetric: Use only if maternal benefit outweighs fetal risk.

Adverse Reactions/Side Effects

Central nervous system

confusion
dizziness
drowsiness
hallucinations
headache

Ear, Eye, Nose, Throat

blurred vision

Gastrointestinal

constipation (most frequent)
dry mouth (most frequent)
dyspepsia
nausea

Metabolic

heat intolerance

Miscellaneous

angioedema (life-threatening)

Interactions

Drug-Drug interaction

Blood levels and risk of toxicity are ↑ by concurrent use of strong CYP3A4 inhibitors including ketoconazole, itraconazole, ritonavir, nelfinavir, clarithromycin, and nefazodone ; daily dose should not exceed 7.5 mg.Concurrent use of moderate inhibitors of CYP3A4, especially those with narrow therapeutic indices, including flecainide, thioridazine, and tricyclic antidepressants, should be undertaken with caution.

Route/Dosage

Oral (Adults) 7.5 mg once daily, may be ↑ after 2 wk to 15 mg once daily.

Availability

Extended-release tablets: 7.5 mg, 15 mg Cost: All strengths $599.48 / 90

Nursing implications

Nursing assessment

Monitor voiding pattern and assess symptoms of overactive bladder (urinary urgency, urinary incontinence, urinary frequency) to and periodically during therapy.

Potential Nursing Diagnoses

Impaired urinary elimination (Indications)

Implementation

Oral: Administer once daily without regard to food. Extended-release tablets must be swallowed whole; do not break, crush, or chew.

Patient/Family Teaching

Instruct patient to take darifenacin as directed. Advise patient to read the Patient Information before starting therapy and with each prescription refill. If a dose is missed, skip dose and take next day; do not take 2 doses in same day.
Do not share darifenacin with others; may be dangerous.
Inform patient of potential anticholinergic side effects (constipation, urinary retention, blurred vision, heat prostration in a hot environment).
May cause dizziness, drowsiness, confusion, and blurred vision. Caution patient to avoid driving and other activities that require alertness until response to medication is known.
Instruct patient to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken and consult health care professional before taking any new medications.
Advise female patient to notify health care professional if pregnancy is planned or suspected or if breast feeding.

Evaluation/Desired Outcomes

Decrease in symptoms of overactive bladder (urge urinary incontinence, urgency, frequency).

darifenacin

Therapeutics An agent in clinical trials for treating irritable bowel syndrome and overactive bladder