Darifenacin Drug Information

Darifenacin extended-release tablets are indicated for the treatment of overactive bladder with symptoms of urge urinary incontinence, urgency and frequency.

The recommended starting dose of darifenacin extended-release tablets is 7.5 mg orally once daily. Based upon individual response, the dose may be increased to 15 mg once daily, as early as two weeks after starting therapy. Darifenacin extended-release tablets should be taken orally once daily with water.

Darifenacin extended-release tablets may be taken with or without food, and should be swallowed whole and not chewed, divided or crushed. For patients with moderate hepatic impairment (Child-Pugh B) or when co-administered with potent CYP3A4 inhibitors (for example, ketoconazole, itraconazole, ritonavir, nelfinavir, clarithromycin and nefazadone), the daily dose of darifenacin extended-release tablets should not exceed 7.5 mg. Darifenacin extended-release tablets are not recommended for use in patients with severe hepatic impairment (Child-Pugh C).

The tablet should be swallowed whole with water and not chewed, divided or crushed

Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. The safety of darifenacin extended-release tablets was evaluated in controlled clinical trials in a total of 8,830 patients, 6,001 of whom were treated with darifenacin extended-release tablets. In Studies 1, 2 and 3 combined, the serious adverse reactions to darifenacin extended-release tablets were urinary retention and constipation.

In these studies, the most frequently reported adverse reactions were dry mouth and constipation. The majority of the adverse reactions were mild or moderate in severity and most occurred during the first two weeks of treatment. Table 1: Incidence of Identified Adverse Reactions, Derived from All Adverse Events Reported in greater than or equal to 2% of Patients Treated with Darifenacin Extended-Release Tablets and More Frequent with Darifenacin Extended-Release Tablets than with Placebo in Studies 1, 2, and 3 Other adverse reactions reported by 1% to 2% of darifenacin extended-release tablets -treated patients include: abnormal vision, accidental injury, back pain, dry skin, flu syndrome, hypertension, vomiting, peripheral edema, weight gain, arthralgia, bronchitis, pharyngitis, rhinitis, sinusitis, rash, pruritus, urinary tract disorder and vaginitis.

Study 4 was a randomized, 12-week, placebo-controlled, dose-titration regimen study in which darifenacin extended-release tablets was administered in accordance with dosing recommendations. All patients initially received placebo or darifenacin extended-release tablets 7.5 mg daily, and after two weeks, patients and physicians were allowed to adjust upward to darifenacin extended-release tablets 15 mg if needed. In this study, the most commonly reported adverse reactions were also constipation and dry mouth.

Table 2: Number (%) of Adverse Reactions, Derived from All Adverse Events Reported in greater than 3% of Patients Treated with Darifenacin Extended-Release Tablets, and More Frequent with Darifenacin Extended-Release Tablets than Placebo, in Study 4 Post Marketing Experience The following adverse reactions have been reported during post-approval use of darifenacin extended-release tablets. 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

CYP3A4 Inhibitors

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 tablets 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).

CYP2D6 Inhibitors

No dosing adjustments are recommended in the presence of CYP2D6 inhibitors (for example, paroxetine, fluoxetine, quinidine and duloxetine).

CYP2D6 Substrates Caution should be taken when darifenacin extended-release tablets are used concomitantly with medications that are predominantly metabolized by CYP2D6 and which have a narrow therapeutic window (for example, flecainide, thioridazine and tricyclic antidepressants).

CYP3A4 Substrates Darifenacin (30 mg daily) did not have a significant impact on midazolam (7.5 mg) pharmacokinetics.

Combination oral contraceptives Darifenacin (10 mg three times daily) had no effect on the pharmacokinetics of the combination oral contraceptives containing levonorgestrel and ethinyl estradiol.

Warfarin 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.

Digoxin 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.

Other Anticholinergic Agents

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.

Pregnancy Risk Summary There are no available data on darifenacin extended-release tablets 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 respectively. Data Animal Data Embryofetal development studies were conducted with oral darifenacin in female rats mg/kg/day and rabbits 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).

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 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.

Pediatric Use The safety and effectiveness of darifenacin extended-release tablets in pediatric patients have not been established.

Darifenacin extended-release tablets are contraindicated in patients with, or at risk for, the following conditions: urinary retention gastric retention, or uncontrolled narrow-angle glaucoma.

Overdosage with antimuscarinic agents, including darifenacin extended-release tablets, can result in severe antimuscarinic effects. Treatment should be symptomatic and supportive. In the event of overdosage, ECG monitoring is recommended.

Darifenacin extended-release tablets have been administered in clinical trials at doses up to 75 mg (five times the maximum therapeutic dose) and signs of overdose were limited to abnormal vision.