ENABLEX
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ENABLEX (ENABLEX).
Darifenacin is a competitive muscarinic receptor antagonist with high affinity for the M3 receptor subtype, which is involved in urinary bladder contraction and salivary secretion. It reduces detrusor muscle overactivity by blocking acetylcholine binding at muscarinic receptors in the bladder.
| Metabolism | Extensively metabolized in the liver primarily via cytochrome P450 (CYP) 2D6 and CYP3A4 enzymes. Two major metabolites (one active) are formed, with the active metabolite having about 1/3 the potency of darifenacin. |
| Excretion | Renal (70% as metabolites, <1% unchanged), fecal (20%) |
| Half-life | 13 hours; steady-state achieved within 3-5 days |
| Protein binding | 50% bound; primarily to albumin |
| Volume of Distribution | 2.7 L/kg; extensive tissue distribution |
| Bioavailability | Oral: 80% |
| Onset of Action | Oral: 1-2 hours |
| Duration of Action | 12-24 hours; dosing every 12 hours maintains continuous effect |
7.5 mg to 15 mg orally once daily.
| Dosage form | TABLET, EXTENDED RELEASE |
| Renal impairment | No adjustment required for mild to moderate renal impairment (CrCl ≥30 mL/min). Not recommended in severe renal impairment (CrCl <30 mL/min). |
| Liver impairment | No adjustment for mild hepatic impairment (Child-Pugh A). For moderate impairment (Child-Pugh B), maximum dose is 7.5 mg once daily. Not recommended in severe impairment (Child-Pugh C). |
| Pediatric use | Not approved for pediatric use. |
| Geriatric use | Initiate at 7.5 mg once daily; may increase to 15 mg once daily based on tolerability and response. Monitor for anticholinergic effects. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ENABLEX (ENABLEX).
| Breastfeeding | Excreted into breast milk in rats; unknown in humans. M/P ratio not determined. Weigh benefits against potential risks; caution in nursing infants. |
| Teratogenic Risk | Pregnancy Category B. No evidence of teratogenicity in animal studies. Limited human data; however, no increased risk of major birth defects has been reported. Use only if clearly needed, especially during first trimester. |
| Fetal Monitoring |
■ FDA Black Box Warning
None
| Serious Effects |
["Urinary retention","Gastric retention","Uncontrolled narrow-angle glaucoma","Hypersensitivity to darifenacin or any excipient of the product"]
| Precautions | ["Angioedema and anaphylactic reactions have been reported, requiring immediate discontinuation and appropriate therapy","May worsen symptoms of myasthenia gravis due to anticholinergic effects","Use with caution in patients with bladder outlet obstruction due to risk of urinary retention","Use with caution in patients with decreased gastrointestinal motility (e.g., severe constipation, ulcerative colitis) due to risk of gastric retention","May exacerbate angle-closure glaucoma; use with caution in patients treated for narrow-angle glaucoma","Hepatic impairment: not recommended for use in patients with severe hepatic impairment (Child-Pugh class C); dose adjustment recommended for moderate impairment (maximum 7.5 mg/day)","Renal impairment: use with caution in patients with severe renal impairment (CrCl <30 mL/min) due to increased exposure"] |
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| Monitor for anticholinergic effects (dry mouth, constipation, blurred vision) and urinary retention. No specific fetal monitoring required; routine prenatal care advised. |
| Fertility Effects | No evidence of impaired fertility in animal studies; no human data available. Theoretical possibility of anticholinergic effects on reproductive function. |