Oxybutynin

12.1 Mechanism of Action Oxybutynin relaxes bladder smooth muscle. Oxybutynin chloride exerts a direct antispasmodic effect on smooth muscle and inhibits the muscarinic action of acetylcholine on smooth muscle. No blocking effects occur at skeletal neuromuscular junctions or autonomic ganglia (antinicotinic effects). Antimuscarinic activity resides predominantly in the R-isomer. A metabolite, desethyloxybutynin, has pharmacological activity similar to that of oxybutynin in in vitro studies.

1 INDICATIONS AND USAGE Oxybutynin chloride extended-release tablets are a muscarinic antagonist indicated for the treatment of overactive bladder with symptoms of urge urinary incontinence, urgency, and frequency. Oxybutynin chloride extended-release tablets are also indicated for the treatment of pediatric patients aged 6 years and older with symptoms of detrusor overactivity associated with a neurological condition (e.g., spina bifida). Oxybutynin chloride extended-release tablets are a muscarinic antagonist indicated for the treatment of overactive bladder with symptoms of urge urinary incontinence, urgency, and frequency. (1) Oxybutynin chloride extended-release tablets are also indicated for the treatment of pediatric patients aged 6 years and older with symptoms of detrusor overactivity associated with a neurological condition (e.g., spina bifida). (1)

2 DOSAGE AND ADMINISTRATION Oxybutynin chloride extended-release tablets must be swallowed whole with the aid of liquids, and must not be chewed, divided, or crushed. Oxybutynin chloride extended-release tablets may be administered with or without food. Oxybutynin chloride extended-release tablets must be swallowed whole with the aid of liquids, and must not be chewed, divided, or crushed. Oxybutynin chloride extended-release tablets may be administered with or without food. (2) Adults: Start with 5 mg or 10 mg, once daily at approximately the same time every day. Dose should not exceed 30 mg per day. ( 2.1 ) Pediatric patients (6 years of age or older): Start with 5 mg, once daily at approximately the same time every day. Dose should not exceed 20 mg per day. ( 2.2 ) 2.1 Adults The recommended starting dose of Oxybutynin chloride extended-release tablets is 5 or 10 mg once daily at approximately the same time each day. Dosage may be adjusted in 5-mg increments to achieve a balance of efficacy and tolerability (up to a maximum of 30 mg/day). In general, dosage adjustment may proceed at approximately weekly intervals. 2.2 Pediatric Patients Aged 6 Years of Age and Older The recommended starting dose of Oxybutynin chloride extended-release tablets is 5 mg once daily at approximately the same time each day. Dosage may be adjusted in 5-mg increments to achieve a balance of efficacy and tolerability (up to a maximum of 20 mg/day).

6 ADVERSE REACTIONS The most common (incidence ≥5%) adverse reactions were dry mouth, constipation, diarrhea, headache, somnolence, and dizziness. (6) To report SUSPECTED ADVERSE REACTIONS, contact AvKARE, Inc. at 1-855-361-3993 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, the 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 clinical practice. The safety and efficacy of Oxybutynin chloride extended-release tablets (5 to 30 mg/day) was evaluated in 774 adult subjects who participated in five double-blind, controlled clinical trials. In four of the five studies, Oxybutynin chloride IR (5 to 20 mg/day in 199 subjects) was an active comparator. Adverse reactions reported by ≥ 1% of subjects are shown in Table 1. Table 1: Adverse Drug Reactions Reported by ≥ 1% of Oxybutynin chloride extended-release tablets-treated Adult Subjects in Five Double-blind, Controlled Clinical Trials of Oxybutynin chloride extended-release tablets System/Organ Class Preferred Term Oxybutynin chloride extended-release tablets 5 to 30 mg/day n = 774 % Oxybutynin chloride IR IR = immediate release 5 to 20 mg/day n = 199 % Psychiatric Disorders Insomnia 3.0 5.5 Nervous System Disorders Headache 7.5 8.0 Somnolence 5.6 14.1 Dizziness 5.0 16.6 Dysgeusia 1.6 1.5 Eye Disorders Vision blurred 4.3 9.6 Dry eye 3.1 2.5 Respiratory, Thoracic and Mediastinal Disorders Cough 1.9 3.0 Oropharyngeal pain 1.9 1.5 Dry throat 1.7 2.5 Nasal dryness 1.7 4.5 Gastrointestinal Disorders Dry mouth 34.9 72.4 Constipation 8.7 15.1 Diarrhea 7.9 6.5 Dyspepsia 4.5 6.0 Nausea 4.5 11.6 Abdominal pain 1.6 2.0 Vomiting 1.3 1.5 Flatulence 1.2 2.5 Gastro-esophageal reflux disease 1.0 0.5 Skin and Subcutaneous Tissue Disorders Dry skin 1.8 2.5 Pruritus 1.3 1.5 Renal and Urinary Disorders Dysuria 1.9 2.0 Urinary hesitation 1.9 8.5 Urinary retention 1.2 3.0 General Disorders and Administration Site Conditions Fatigue 2.6 3.0 Investigations Residual urine volume The bundled term residual urine volume consists of the preferred terms residual urine volume and residual urine volume increased. 2.3 3.5 The discontinuation rate due to adverse reactions was 4.4% with Oxybutynin chloride extended-release tablets compared to 0% with Oxybutynin chloride IR. The most frequent adverse reaction causing discontinuation of study medication was dry mouth (0.7% ). The following adverse reactions were reported by <1% of Oxybutynin chloride extended-release tablets-treated patients and at a higher incidence than placebo in clinical trials: Metabolism and Nutrition Disorders: anorexia, fluid retention; Vascular disorders: hot flush; Respiratory, thoracic and mediastinal disorders: dysphonia; Gastrointestinal Disorders: dysphagia, frequent bowel movements; General disorders and administration site conditions: chest discomfort, thirst. 6.2 Postmarketing Experience The following additional adverse reactions have been reported from worldwide postmarketing experience with Oxybutynin chloride extended-release tablets. Because postmarketing reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. Infections and Infestations: Urinary tract infection; Psychiatric Disorders: psychotic disorder, agitation, confusional state, hallucinations, memory impairment; Nervous System Disorders: convulsions; Eye Disorders: glaucoma; Respiratory, Thoracic and Mediastinal Disorders: nasal congestion; Cardiac Disorders: arrhythmia, tachycardia, palpitations; QT interval prolongation; Vascular Disorders: flushing, hypertension; Skin and Subcutaneous Tissue Disorders: rash; Renal and Urinary Disorders: impotence;General Disorders and Administration Site Conditions: hypersensitivity reactions, including angioedema with airway obstruction, urticaria, and face edema; anaphylactic reactions requiring hospitalization for emergency treatment; Injury, poisoning and procedural complications: fall. Additional adverse events reported with some other oxybutynin chloride formulations include: cycloplegia, mydriasis, and suppression of lactation. To report SUSPECTED ADVERSE REACTIONS contact AvKARE, Inc. at 1-855-361-3993; email drugsafety@avkare.com ; or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch .

7 DRUG INTERACTIONS The concomitant use of oxybutynin with other anticholinergic drugs or with other agents which produce dry mouth, constipation, somnolence (drowsiness), and/or other anticholinergic-like effects may increase the frequency and/or severity of such effects. Anticholinergic agents may potentially alter the absorption of some concomitantly administered drugs due to anticholinergic effects on gastrointestinal motility. This may be of concern for drugs with a narrow therapeutic index. Anticholinergic agents may also antagonize the effects of prokinetic agents, such as metoclopramide. Mean oxybutynin chloride plasma concentrations were approximately 2 fold higher when Oxybutynin chloride extended-release tablets were administered with ketoconazole, a potent CYP3A4 inhibitor. Other inhibitors of the cytochrome P450 3A4 enzyme system, such as antimycotic agents (e.g., itraconazole and miconazole) or macrolide antibiotics (e.g., erythromycin and clarithromycin), may alter oxybutynin mean pharmacokinetic parameters (i.e., C max and AUC). The clinical relevance of such potential interactions is not known. Caution should be used when such drugs are co-administered. Co-administration with other anticholinergic drugs may increase the frequency and/or severity of anticholinergic-like effects. (7) Co-administration with strong cytochrome P450 (CYP) 3A4 inhibitors (e.g., ketoconazole) increases the systemic exposure of oxybutynin. (7)