Enablex

Each tablet contains 7.5 mg of darifenacin (as hydrobromide).
Excipients/Inactive Ingredients: Tablet core: Anhydrous calcium hydrogen phosphate, Hypromellose, Magnesium stearate.
Film coat: Polyethylene glycol, Hypromellose, Titanium dioxide (E171), Talc.

Pharmacotherapeutic group: Urinary antispasmodics. ATC code: G04B D10.
Pharmacology: Pharmacodynamics: Darifenacin is a selective muscarinic M3 receptor antagonist (M₃ SRA) in vitro. The M3 receptor is the major subtype that controls urinary bladder muscle contraction. It is not known whether this selectivity for the M3 receptor translates into any clinical advantage when treating symptoms of overactive bladder syndrome.
Cystometric studies performed with darifenacin in patients with involuntary bladder contractions showed increased bladder capacity, increased volume threshold for unstable contractions and diminished frequency of unstable detrusor contractions.
Treatment with ENABLEX administered at dosages of 7.5 mg and 15 mg daily has been investigated in four double-blind, Phase III, randomized, controlled clinical studies in male and female patients with symptoms of overactive bladder. As seen in Table 1 as follows, a pooled analysis of 3 of the studies for the treatment with both ENABLEX 7.5 mg and 15 mg provided a statistically significant improvement in the primary endpoint, reduction in incontinence episodes versus placebo. (See Table 1.)

Click on icon to see table/diagram/image

ENABLEX 7.5 mg and 15 mg doses significantly reduced both the severity and number of urinary urgency episodes and the number of micturitions, while significantly increasing the mean volume voided from baseline.
ENABLEX 7.5 mg and 15 mg were associated with statistically significant improvements over placebo in some aspects of quality of life as measured by the Kings Health Questionnaire including incontinence impact, role limitations, social limitations and severity measures.
For both doses of 7.5 mg and 15 mg, the percentage median reduction from baseline in the number of incontinence episodes per week was similar between males and females. The observed differences from placebo for males in terms of percentage and absolute reductions in incontinence episodes was lower than females.
The effect of treatment with 15 mg and 75 mg of darifenacin on QT/QTc interval was evaluated in a study in 179 healthy adults (44% male; 56% females) aged 18 to 65 for 6 days (to steady state). Therapeutic and supra-therapeutic doses of darifenacin resulted in no increase in QT/QTc interval prolongation from baseline compared to placebo at maximum darifenacin exposure.
Pharmacokinetics: Darifenacin is metabolized by CYP3A4 and CYP2D6. Due to genetic differences, about 7% of the Caucasians lack the CYP2D6 enzyme and are said to be poor metabolisers. A few percent of the population have increased CYP2D6 enzyme levels (ultrafast metabolisers). The following information applies to subjects who have normal CYP2D6 activity (extensive metabolisers) unless otherwise stated.
Absorption: Due to extensive first-pass metabolism darifenacin has a bioavailability of approximately 15% and 19% after 7.5 mg and 15 mg daily doses at steady state. Maximum plasma levels are reached approximately 7 hours after administration of the prolonged-release tablets and steady-state plasma levels are achieved by the sixth day of administration. At steady state, peak-to-trough fluctuations in darifenacin concentrations are small (PTF: 0.87 for 7.5 mg and 0.76 for 15 mg), thereby maintaining therapeutic plasma levels over the dosing interval. Food had no effect on darifenacin pharmacokinetics during multiple-dose administration of prolonged-release tablets.
Distribution: Darifenacin is a lipophilic base and is 98% bound to plasma proteins (primarily to alpha-1-acid-glycoprotein). The steady-state volume of distribution (Vss) is estimated to be 163 litres.
Metabolism: Darifenacin is extensively metabolized by the liver following oral administration.
Darifenacin undergoes significant metabolism by cytochrome CYP3A4 and CYP2D6 in the liver and by CYP3A4 in the gut wall. The three main metabolic routes are as follows: monohydroxylation in the dihydrobenzofuran ring; dihydrobenzofuran ring opening; and N-dealkylation of the pyrrolidine nitrogen.
The initial products of the hydrogenation and N-dealkylation pathways are major circulating metabolites but none contribute significantly to the overall clinical effect of darifenacin.
The pharmacokinetics of darifenacin at steady state are dose-dependent, due to saturation of the CYP2D6 enzyme.
Doubling the darifenacin dose from 7.5 mg to 15 mg result in a 150% increase in steady-state exposure. This dose-dependency is probably caused by saturation of the CYP2D6 catalysed metabolism possibly together with some saturation of CYP3A4-mediated gut wall.
Excretion: Following administration of an oral dose of ₁₄C-darifenacin solution to healthy volunteers, approximately 60% of the radioactivity was recovered in the urine and 40% in the faeces. Only a small percentage of the excreted dose was unchanged darifenacin (3%). Estimated darifenacin clearance is 40 litres/hour.
Special patient population: Gender: A population pharmacokinetic analysis of patient data indicated that darifenacin exposure was 23% lower in males than females (see Pharmacodynamics as previously mentioned).
Elderly patients: A population pharmacokinetic analysis of patient data indicated a trend for clearance to decrease with age (19% per decade based on Phase III population pharmacokinetic analysis of patients aged 60-89 years), see Dosage & Administration.
Paediatric patients: The pharmacokinetics of darifenacin have not been established in the paediatric population.
CYP2D6 poor metabolisers: The metabolism of darifenacin in CYP2D6 poor metabolisers is principally mediated by CYP3A4. In one pharmacokinetic study the steady-state exposure in poor metabolisms was 164% and 99% higher during treatment with 7.5 mg and 15 mg once daily, respectively. However, a population pharmacokinetic analyses of Phase III data indicated that on average steady-state exposure is 66% higher in poor metabolisers than in extensive metabolisers. There was considerable overlap between the ranges of exposures seen in these two populations (see Dosage & Administration).
Renal insufficiency: A study of subjects with varying degrees of renal impairment (creatinine clearance between 10 ml/min and 136 ml/min) given darifenacin 15 mg once daily to steady state demonstrated no relationship between renal function and darifenacin clearance (see Dosage & Administration).
Hepatic insufficiency: Darifenacin pharmacokinetics were investigated in subjects with mild (Child Pugh A) or moderate (Child Pugh B) impairment of hepatic function given darifenacin 15 mg once dally to steady state.
Mild hepatic impairment had no effect on the pharmacokinetics of darifenacin. Unbound darifenacin exposure was estimated to be 4.7-fold higher in subjects with moderate hepatic impairment than subjects with normal hepatic function (see Dosage & Administration).
Toxicology: Preclinical safety data: Preclinical data reveal no special hazard for humans based on conventional studies of safety pharmacology, repeated dose toxicity, genotoxicity and carcinogenic potential.
Animal studies do not indicate direct or indirect harmful effects with respect to fertility, pregnancy, embryonal/foetal development. In peri and post natal studies in rats, dystocia, increased foetal deaths in utero, and toxicity to post natal development (pup body weight and development land marks) were observed at systemic exposure levels up to 11 times higher the expected clinical exposure.

Symptomatic treatment of urge incontinence and/or increased urinary frequency and urgency as may occur in patients with overactive bladder syndrome.

For oral use.
Adults (≥18 years): The recommended starting dose is 7.5 mg daily. After 2 weeks of starting therapy, patients should be reassessed. For those patients requiring greater symptom relief, the dose may be increased to 15 mg daily, based on individual response.
ENABLEX should be taken once daily with liquid. The tablets can be taken with or without food, and be swallowed whole and not chewed, divided or crushed.
Elderly patients (≥65 years): The recommended starting dose for the elderly is 7.5 mg daily. After 2 weeks of starting therapy, patients should be reassessed for efficacy and safety. For those patients who have an acceptable tolerability profile but requiring greater symptom relief, the dose may be increased to 15 mg daily, based on individual response (see Pharmacology: Pharmacokinetics under Actions).
Children: No studies have been performed in children. Therefore, until more information is available, ENABLEX is not recommended for use in children.
Use in renal impairment: No dose adjustment is required in patients with impaired renal function. However, caution should be exercised when treating this population (see Pharmacology: Pharmacokinetics under Actions).
Use in hepatic impairment: No dose adjustment is required in patients with mild hepatic impairment (Child Pugh A). However, there is a risk of increased exposure in this population (see Pharmacology: Pharmacokinetics under Actions).
In patients with moderate hepatic impairment (Child Pugh B), patients should only be treated if the benefit outweighs the risk, and patients should be restricted to 7.5 mg daily (see Pharmacology: Pharmacokinetics under Actions).
Patients receiving concomitant treatment with drugs that are potent inhibitors of CYP2D6 or moderate inhibitors of CYP3A4: In patients receiving drugs that are potent CYP2D6 inhibitors such as paroxetine, terbinafine, quinidine and cimetidine, treatment should start with the 7.5 mg dose. The dose may be titrated to 15 mg daily to obtain an improved clinical response provided the dose is well tolerated. However, caution should be exercised.
In patients receiving drugs that are moderate CYP3A4 inhibitors such as fluconazole, grapefruit juice and erythromycin, the recommended starting dose is 7.5 mg daily. The dose may be titrated to 15 mg daily to obtain an improved clinical response provided the dose is well tolerated. However, caution should be exercised.

ENABLEX has been administered in clinical trials at doses up to 75 mg (five times maximum therapeutic dose). The most common adverse events seen were dry mouth, constipation, headache, dyspepsia and nasal dryness. However, overdosages with darifenacin can potentially lead to severe anticholinergic effects and should be treated accordingly. Therapy should be aimed at reversing the anticholinergic symptoms under careful medical supervision. The use of agents such as physostigmine can assist in reversing such symptoms.

ENABLEX is contraindicated in patients with: Hypersensitivity to the active substance or to any of the excipients; Urinary retention; Gastric retention; Uncontrolled narrow-angle glaucoma; Myasthenia gravis; Severe hepatic impairment (Child Pugh C); Severe ulcerative colitis; Toxic megacolon; Concomitant treatment with potent CYP3A4 inhibitors (see Interactions).

ENABLEX should be administered with caution to patients with autonomic neuropathy, hiatus hernia, clinically significant bladder outflow obstruction, risk for urinary retention, severe constipation or gastrointestinal obstructive disorders, such as pyloric stenosis.
ENABLEX should be used with caution in patients being treated for narrow-angle glaucoma (see Contraindications).
Other causes of frequent urination (heart failure or renal disease) should be assessed before treatment with ENABLEX. If urinary tract infection is present, an appropriate antibacterial therapy should be started.
ENABLEX should be used with caution in patients with risk of decreased gastrointestinal motility, gastro-oesophageal reflux and/or who are concurrently taking medicinal products (such as oral bisphosphonates) that can cause or exacerbate oesophagitis.
Safety and efficacy have not yet been established in patients with a neurogenic cause for detrusor overactivity.
Effects on ability to drive and use machines: No studies of the effects of ENABLEX on the ability to drive and use machines have been performed. As with other antimuscarinic agents, caution should be exercised when driving or using machines due to possible occurrence of undesirable effects such as abnormal vision, dizziness, insomnia and somnolence. For ENABLEX, these side effects have been reported to be uncommon.

Pregnancy: There are no studies of darifenacin in pregnant women. Animal studies have shown toxicity to parturition, peri and post-natal development (see Pharmacology: Toxicology: Preclinical safety data under Actions). ENABLEX is not recommended during pregnancy.
Lactation: Darifenacin is excreted into the milk of rats. It is not known whether darifenacin is excreted into human milk and therefore caution should be exercised before ENABLEX is administered to a nursing woman.

Consistent with the pharmacological profile, the most commonly reported adverse drug reactions were dry mouth (20.2% and 35% for the 7.5 mg and 15 mg dose, respectively vs. 8% placebo) and constipation (14.8% and 21% for the 7.5 mg and 15 mg dose, respectively vs. 5.4% placebo). Anticholinergic effects, in general, are dose-dependent.
However, the patient discontinuation rates due to these adverse reactions were low (dry mouth: 0% and 0.9% for the 7.5 mg and 15 mg dose, respectively vs. 0% for placebo; constipation: 0.6% and 1.2% for the 7.5 mg and 15 mg dose, respectively vs. 0.3% for placebo). (See Table 2.)

Click on icon to see table/diagram/image

In the pivotal clinical trials with doses of ENABLEX 7.5 mg and 15 mg, adverse drug reactions were reported as presented in Table 2. Most of the adverse drug reactions were of mild or moderate intensity and did not result in discontinuation in the majority of the patients.
Treatment with ENABLEX may possibly mask symptoms associated with gallbladder disease.
However, there was no association between the occurrence of adverse events related to the biliary system in darifenacin-treated patients and increasing age.
The incidence of adverse events with the doses of ENABLEX 7.5 mg and 15 mg decreased during the treatment period up to 6 months. A similar trend is also seen for the discontinuation rates.

Effects of other medicinal products on darifenacin: Darifenacin metabolism is primarily mediated by the cytochrome P450 enzymes CYP2D6 and CYP3A4. Therefore, inhibitors of these enzymes may increase darifenacin exposure.
CYP2D6 inhibitors: In patients receiving drugs that are potent CYP2D6 inhibitors (e.g. paroxetine, terbinafine, cimetidine and quinidine) the recommended starting dose should be 7.5 mg daily. The dose may be titrated to 15 mg daily to obtain an improved clinical response provided the dose is well tolerated. Concomitant treatment with potent CYP2D6 inhibitors results in an increase in exposure (e.g. of 30% with paroxetine at the 30 mg dose of darifenacin).
CYP3A4 inhibitors: Darifenacin should not be used together with potent CYP3A4 inhibitors (see Contraindications) such as protease inhibitors, ketoconazole and itraconazole. Potent P-glycoprotein inhibitors such as cyclosporine and verapamil should also be avoided. Co-administration of darifenacin 7.5 mg with the potent CYP3A4 inhibitor ketoconazole 400 mg resulted in a 5-fold increase in steady-state darifenacin AUC. In subjects who are poor metabolisers, darifenacin exposure increased by approximately 10-fold. Due to a greater contribution of CYP3A4 after higher darifenacin doses, the magnitude of the effect is expected to be even more pronounced when combining ketoconazole with darifenacin 15 mg.
When co-administered with moderate CYP3A4 inhibitors such as erythromycin, clarithromycin, telithromycin, fluconazole and grapefruit juice, the recommended starting dose of darifenacin should be 7.5 mg daily. The dose may be titrated to 15 mg daily to obtain an improved clinical response provided the dose is well tolerated. Darifenacin AUC₂₄ and C_max from 30 mg od dosing in subjects who are extensive metabolisers were 95% and 128% higher, when erythromycin (moderate CYP3A4 inhibitor) was co-administered with darifenacin than when darifenacin was taken alone.
Enzyme inducers: Drugs that are inducers of CYP3A4 such as rifampicin, carbamazepine, barbiturates and St. John's wort (Hypericum perforatum) are likely to decrease the plasma concentrations of darifenacin.
Effects of darifenacin on other medicinal products: CYP2D6 substrates: Darifenacin is a moderate inhibitor of the enzyme CYP2D6. Caution should be exercised when darifenacin is used concomitantly with medicinal products that are predominantly metabolized by CYP2D6 and which have a narrow therapeutic window, such as flecainide, thioridazine, or tricyclic antidepressants such as imipramine. The effects of darifenacin on the metabolism of CYP2D6 substrates are mainly clinically relevant for CYP2D6 substrate which are individually dose titrated.
CYP3A4 substrates: Darifenacin treatment resulted in a modest increase in the exposure of the CYP3A4 substrate midazolam. The interaction with midazolam lacks clinical relevance but is indicative of a slight CYP3A4 inhibition by darifenacin.
Warfarin: Standard therapeutic prothrombin time monitoring for warfarin should be continued. The effect of warfarin on prothrombin time was not altered when co-administered with darifenacin.
Digoxin: Therapeutic drug monitoring for digoxin should be performed when initiating and ending darifenacin treatment as well as changing the darifenacin dose. Darifenacin 30 mg once daily (two times greater than the recommended daily dose) co-administered with digoxin at steady state resulted in a small increase in digoxin exposure (AUC: 16% and C_max: 20%). The increase in digoxin exposure could be caused by competition between darifenacin and digoxin for P-glycoprotein. Other transporter-related interactions cannot be excluded.
Antimuscarinic agents: As with any other antimuscarinic agents, the concomitant medication with medicinal products that possess antimuscarinic properties, such as oxybutynin, tolterodine and flavoxate may result in more pronounced therapeutic and side effects. The potentiation of anticholinergic effects with anti-parkinson agents and tricyclic antidepressants may also occur if antimuscarinic agents are used concurrently with such medicinal products. However, no studies involving the interaction with anti-parkinson agents and tricyclic antidepressants have been performed.

Instructions for use, handling and disposal: No special requirements.
Incompatibilities: Not applicable.

Store the blister packs in the outer carton in order to protect from light.
Shelf life: 3 years.

Drugs for Bladder & Prostate Disorders

G04BD10 - darifenacin ; Belongs to the class of urinary antispasmodics.

P₁S₁S₃