The following adverse reactions have been reported during post-approval use of darifenacin extended-release tablets (darifenacin). Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate frequency or establish a causal relationship to drug exposure.
Dermatologic: erythema multiforme, interstitial granuloma annulare
General: hypersensitivity reactions, including angioedema with airway obstruction and anaphylactic reaction
Central Nervous: confusion, hallucinations and somnolence
Cardiovascular: palpitations and syncope
The systemic exposure of darifenacin from darifenacin extended-release tablets is increased in the presence of CYP3A4 inhibitors. The daily dose of darifenacin extended-release tablet should not exceed 7.5 mg when co-administered with potent CYP3A4 inhibitors (for example, ketoconazole, itraconazole, ritonavir, nelfinavir, clarithromycin and nefazadone). No dosing adjustments are recommended in the presence of moderate CYP3A4 inhibitors (for example, erythromycin, fluconazole, diltiazem and verapamil) [see Dosage and Administration (2) and Clinical Pharmacology (12.3)].
No dosing adjustments are recommended in the presence of CYP2D6 inhibitors (for example, paroxetine, fluoxetine, quinidine and duloxetine) [see Clinical Pharmacology (12.3)].
Caution should be taken when darifenacin extended-release tablet is used concomitantly with medications that are predominantly metabolized by CYP2D6 and which have a narrow therapeutic window (for example, flecainide, thioridazine and tricyclic antidepressants) [see Clinical Pharmacology (12.3)].
Darifenacin (30 mg daily) did not have a significant impact on midazolam (7.5 mg) pharmacokinetics [see Clinical Pharmacology (12.3)].
Darifenacin (10 mg three times daily) had no effect on the pharmacokinetics of the combination oral contraceptives containing levonorgestrel and ethinyl estradiol [see Clinical Pharmacology (12.3)].
Darifenacin had no significant effect on prothrombin time when a single dose of warfarin 30 mg was co-administered with darifenacin (30 mg daily) at steady-state. Standard therapeutic prothrombin time monitoring for warfarin should be continued.
Darifenacin (30 mg daily) did not have a clinically relevant effect on the pharmacokinetics of digoxin (0.25 mg) at steady-state. Routine therapeutic drug monitoring for digoxin should be continued [see Clinical Pharmacology (12.3)].
The concomitant use of darifenacin extended-release tablets with other anticholinergic agents may increase the frequency and/or severity of dry mouth, constipation, blurred vision and other anticholinergic pharmacological effects. Anticholinergic agents may potentially alter the absorption of some concomitantly administered drugs due to effects on gastrointestinal motility.
There are no available data on darifenacin use in pregnant women to evaluate for a drug-associated risk of major birth defects, miscarriage, or other adverse maternal or fetal outcomes. In animal studies, darifenacin was not teratogenic in rats and rabbits at plasma exposures of free drug (via AUC) up to 59 and 28 times the maximum recommended human dose (MRHD) of 15 mg, respectively. Effects on embryofetal development were observed following administration of darifenacin during pregnancy (dilated ureter and/or kidney pelvis in rabbits at about 9 times the MRHD, post-implantation loss in rabbits at about 28 times, and delayed ossification in rats at about 59 times) and during pregnancy and lactation (developmental delays in rats at about 17 times the MRHD), which was associated with maternal toxicity (see Data). Dystocia was observed in rat dams at about 17 times the MRHD.
In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2-4% and 15-20%, respectively.
Embryofetal development studies were conducted with oral darifenacin in female rats (0, 3, 10, and 50 mg/kg/day) and rabbits (0, 3, 10, and 30 mg/kg/day) during the period of organogenesis (gestation days 6 to 17 in the rat and gestation days 6 to 18 in the rabbit).
Darifenacin was not teratogenic in rats and rabbits at plasma exposures of free drug (via AUC) up to 59 times and 28 times, respectively (doses up to 50 and 30 mg/kg/day, respectively) the maximum recommended human dose [MRHD] of 15 mg.
At approximately 59 times the MRHD in pregnant rats, there was a delay in the ossification of the sacral and caudal vertebrae (associated with a decrease in maternal and pup body weight gains) which was not observed at an exposure approximately 13 times the AUC at the MRHD. At five times the AUC (3 mg/kg/day), there were no effects on dams or pups.
In pregnant rabbits, an exposure of darifenacin approximately 28 times the AUC at the MRHD of 15 mg (30 mg/kg/day) was shown to increase post-implantation loss (associated with decreased maternal body weight gain), with a no effect level at 10 mg/kg/day (9 times the AUC at the MRHD). Dilated ureter and/or kidney pelvis was also observed in offspring at this highest dose along with urinary bladder dilation consistent with the pharmacological action of darifenacin, with one case observed at the mid dose of 10 mg/kg/day (9 times the MRHD). No effect was observed at the lowest dose of 3 mg/kg/day (approximately 2.8 times the AUC at the MRHD).
A pre- and post-natal development study was conducted with oral darifenacin in female rats (0, 3, 10, and 50 mg/kg/day) throughout gestation and lactation. Decreased body weight gain and dystocia were observed in dams at 10 mg/kg/day (approximately 17 times the MRHD) and above. Slight developmental delays (surface righting reflex, incisor eruption, eyelid opening, vaginal opening, preputial separation) were observed in pups at these doses. At 5 times the AUC at the MRHD (3 mg/kg/day), there were no effects on dams or pups.
There are no data on the presence of darifenacin in human milk, the effects on the breastfed infant, or the effects of darifenacin on milk production. Darifenacin is present in rat milk [see Data]. When a drug is present in animal milk, it is likely that the drug will be present in human milk.
The developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for darifenacin and any potential adverse effects on the breastfed child from darifenacin or from the underlying maternal conditions.
After a single oral dose of 14 C radiolabeled darifenacin to lactating rats, darifenacin was detected in maternal milk.
In the fixed-dose, placebo-controlled, clinical studies, 30% of patients treated with darifenacin extended-release tablets were over 65 years of age. No overall differences in safety or efficacy were observed between patients over 65 years (n = 207) and younger patients less than 65 years (n = 464). No dose adjustment is recommended for elderly patients [see Clinical Pharmacology (12.3) and Clinical Studies (14)].
Subjects with severe hepatic impairment (Child-Pugh C) have not been studied, therefore darifenacin extended-release tablet is not recommended for use in these patients [see Dosage and Administration (2) and Warnings and Precautions (5.6)]. The daily dose of darifenacin extended-release tablet should not exceed 7.5 mg once daily for patients with moderate hepatic impairment (Child-Pugh B) [see Dosage and Administration (2) and Warnings and Precautions (5.6)]. After adjusting for plasma protein binding, unbound darifenacin exposure was estimated to be 4.7-fold higher in subjects with moderate hepatic impairment than subjects with normal hepatic function. No dose adjustment is recommended for patients with mild hepatic impairment (Child-Pugh A).
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