Oxybutynin Chloride (oxybutynin chloride 15 mg) Dailymed

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) 

8 Use In Specific Populations

• Pediatric Use: Oxybutynin chloride extended-release tablets are not recommended in pediatric patients who cannot swallow the tablet whole without chewing, dividing or crushing, or in children under the age of 6 years. (8.4)
• Renal or Hepatic Impairment: There have been no studies conducted in patients with renal or hepatic impairment. (8.6, 8.7)

8.1 Pregnancy

Pregnancy Category B. There are no adequate and well-controlled studies using Oxybutynin chloride extended-release tablets in pregnant women. Oxybutynin chloride extended-release tablets should be used during pregnancy only if the potential benefit to the patient outweighs the risk to the patient and fetus. Women who become pregnant during Oxybutynin chloride extended-release tablets treatment are encouraged to contact their physician.

Risk Summary

Based on animal data, oxybutynin is predicted to have a low probability of increasing the risk of adverse developmental effects above background risk.

Animal Data

Reproduction studies with oxybutynin chloride in the mouse, rat, hamster, and rabbit showed no evidence of impaired fertility or harm to the animal fetus.

8.3 Nursing Mothers

It is not known whether oxybutynin is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when Oxybutynin chloride extended-release tablets are administered to a nursing woman.

8.4 Pediatric Use

The safety and efficacy of Oxybutynin chloride extended-release tablets were studied in 60 children in a 24-week, open-label, non-randomized trial. Patients were aged 6–15 years, all had symptoms of detrusor overactivity in association with a neurological condition (e.g., spina bifida), all used clean intermittent catheterization, and all were current users of oxybutynin chloride. Study results demonstrated that administration of Oxybutynin chloride extended-release tablets 5 to 20 mg/day was associated with an increase from baseline in mean urine volume per catheterization from 108 mL to 136 mL, an increase from baseline in mean urine volume after morning awakening from 148 mL to 189 mL, and an increase from baseline in the mean percentage of catheterizations without a leaking episode from 34% to 51%.

Urodynamic results were consistent with clinical results. Administration of Oxybutynin chloride extended-release tablets resulted in an increase from baseline in mean maximum cystometric capacity from 185 mL to 254 mL, a decrease from baseline in mean detrusor pressure at maximum cystometric capacity from 44 cm H ₂O to 33 cm H ₂O, and a reduction in the percentage of patients demonstrating uninhibited detrusor contractions (of at least 15 cm H ₂O) from 60% to 28%.

The pharmacokinetics of Oxybutynin chloride extended-release tablets in these patients were consistent with those reported for adults [see Clinical Pharmacology (12.3)].

Oxybutynin chloride extended-release tablets are not recommended in pediatric patients who cannot swallow the tablet whole without chewing, dividing, or crushing, or in children under the age of 6.

8.5 Geriatric Use

The rate and severity of anticholinergic effects reported by patients less than 65 years old and those 65 years and older were similar. The pharmacokinetics of Oxybutynin chloride extended-release tablets were similar in all patients studied (up to 78 years of age).

8.6 Renal Impairment

There were no studies conducted with Oxybutynin chloride extended-release tablets in patients with renal impairment.

8.7 Hepatic Impairment

There were no studies conducted with Oxybutynin chloride extended-release tablets in patients with hepatic impairment.

10 Overdosage

The continuous release of oxybutynin from Oxybutynin chloride extended-release tablets should be considered in the treatment of overdosage. Patients should be monitored for at least 24 hours. Treatment should be symptomatic and supportive. Activated charcoal as well as a cathartic may be administered.

Overdosage with oxybutynin chloride has been associated with anticholinergic effects including central nervous system excitation, flushing, fever, dehydration, cardiac arrhythmia, vomiting, and urinary retention.

Ingestion of 100 mg oxybutynin chloride in association with alcohol has been reported in a 13-year-old boy who experienced memory loss, and a 34-year-old woman who developed stupor, followed by disorientation and agitation on awakening, dilated pupils, dry skin, cardiac arrhythmia, and retention of urine. Both patients fully recovered with symptomatic treatment.

11 Description

Oxybutynin chloride extended-release tablets are an antispasmodic, muscarinic antagonist. Each Oxybutynin chloride extended-release tablets contains 5 mg, 10 mg, or 15 mg of oxybutynin chloride USP, formulated as a once-a-day controlled-release tablet for oral administration. Oxybutynin chloride is administered as a racemate of R- and S-enantiomers.

Chemically, oxybutynin chloride is d,l (racemic) 4-diethylamino-2-butynyl phenylcyclohexylglycolate hydrochloride. The empirical formula of oxybutynin chloride is C ₂₂H ₃₁NO ₃•HCl.

Its structural formula is:

Oxybutynin chloride is a white crystalline solid with a molecular weight of 393.9. It is readily soluble in water and acids, but relatively insoluble in alkalis.

Oxybutynin chloride extended-release tablets also contain the following inert ingredients: lactose, mannitol, dextrose, tartaric acid, colloidal silicon dioxide, magnesium stearate, cellulose acetate, polyethylene glycol, titanium dioxide, triacetin, black iron oxide, propylene glycol, hypromellose.

System Components and Performance

Oxybutynin chloride extended-release tablets uses osmotic pressure to deliver oxybutynin chloride at a controlled rate over approximately 24 hours.  The system, which resembles a conventional tablet in appearance, comprises an osmotically active core surrounded by a semipermeable membrane.  The unitary tablet core is composed of the drug and excipients (including the osmotically active components).  There is a precision-laser drilled orifice in the semipermeable membrane on the side of the tablet.  In an aqueous environment, such as the gastrointestinal tract, water permeates through the membrane into the tablet core, causing the drug to go into suspension and the osmotic components to expand.  This expansion pushes the drug out through the orifice.  The semipermeable membrane controls the rate at which water permeates into the tablet core, which in turn controls the rate of drug delivery.  The controlled rate of drug delivery into the gastrointestinal lumen is thus independent of pH or gastrointestinal motility.  The function of Oxybutynin chloride extended-release tablets depends on the existence of an osmotic gradient between the contents of the core and the fluid in the gastrointestinal tract.  Since the osmotic gradient remains constant, drug delivery remains essentially constant.  The biologically inert components of the tablet remain intact during gastrointestinal transit and are eliminated in the feces as an insoluble shell.

USP Drug Release Test 3.

12 Clinical Pharmacology

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.

12.2 Pharmacodynamics

In patients with conditions characterized by involuntary bladder contractions, cystometric studies have demonstrated that oxybutynin increases bladder (vesical) capacity, diminishes the frequency of uninhibited contractions of the detrusor muscle, and delays the initial desire to void.

12.3 Pharmacokinetics

Absorption

Following the first dose of Oxybutynin chloride extended-release tablets, oxybutynin plasma concentrations rise for 4 to 6 hours; thereafter steady concentrations are maintained for up to 24 hours, minimizing fluctuations between peak and trough concentrations associated with oxybutynin.

The relative bioavailabilities of R- and S-oxybutynin from Oxybutynin chloride extended-release tablets are 156% and 187%, respectively, compared with oxybutynin. The mean pharmacokinetic parameters for R- and S-oxybutynin are summarized in Table 2. The plasma concentration-time profiles for R- and S-oxybutynin are similar in shape; Figure 1 shows the profile for R-oxybutynin.

Table 2: Mean (SD) R- and S-Oxybutynin Pharmacokinetic Parameters Following a Single Dose of Oxybutynin chloride extended-release tablets 10 mg (n=43)

Parameters (units)	R-Oxybutynin		S-Oxybutynin
C max (ng/mL)	1.0	(0.6)	1.8	(1.0)
T max (h)	12.7	(5.4)	11.8	(5.3)
t 1/2 (h)	13.2	(6.2)	12.4	(6.1)
AUC (0–48) (ng∙h/mL)	18.4	(10.3)	34.2	(16.9)
AUC inf (ng∙h/mL)	21.3	(12.2)	39.5	(21.2)

Figure 1: Mean R-oxybutynin plasma concentrations following a single dose of Oxybutynin chloride extended-release tablets 10 mg and oxybutynin 5 mg administered every 8 hours (n=23 for each treatment).



Steady state oxybutynin plasma concentrations are achieved by Day 3 of repeated Oxybutynin chloride extended-release tablets dosing, with no observed drug accumulation or change in oxybutynin and desethyloxybutynin pharmacokinetic parameters.

Oxybutynin chloride extended-release tablets steady state pharmacokinetics were studied in 19 children aged 5–15 years with detrusor overactivity associated with a neurological condition (e.g., spina bifida). The children were on Oxybutynin chloride extended-release tablets total daily dose ranging from 5 to 20 mg (0.10 to 0.77 mg/kg). Sparse sampling technique was used to obtain serum samples. When all available data are normalized to an equivalent of 5 mg per day of Oxybutynin chloride extended-release tablets, the mean pharmacokinetic parameters derived for R- and S-oxybutynin and R- and S-desethyloxybutynin are summarized in Table 3. The plasma-time concentration profiles for R- and S-oxybutynin are similar in shape; Figure 2 shows the profile for R-oxybutynin when all available data are normalized to an equivalent of 5 mg per day.

Table 3: Mean ± SD R- and S-Oxybutynin and R- and S-Desethyloxybutynin Pharmacokinetic Parameters in Children Aged 5–15 Following Administration of 5 to 20 mg Oxybutynin chloride extended-release tablets Once Daily (n=19), All Available Data Normalized to an Equivalent of Oxybutynin chloride extended-release tablets 5 mg Once Daily

	R-Oxybutynin	S-Oxybutynin	R- Desethyloxybutynin	S- Desethyloxybutynin
C max (ng/mL)	0.7 ± 0.4	1.3 ± 0.8	7.8 ± 3.7	4.2 ± 2.3
T max (h)	5.0	5.0	5.0	5.0
AUC (ng∙h/mL)	12.8 ± 7.0	23.7 ± 14.4	125.1 ± 66.7	73.6 ± 47.7

Figure 2: Mean steady state (± SD) R-oxybutynin plasma concentrations following administration of 5 to 20 mg Oxybutynin chloride extended-release tablets once daily in children aged 5–15. Plot represents all available data normalized to an equivalent of Oxybutynin chloride extended-release tablets 5 mg once daily.

Food Effects

The rate and extent of absorption and metabolism of oxybutynin are similar under fed and fasted conditions.

Distribution

Oxybutynin is widely distributed in body tissues following systemic absorption. The volume of distribution is 193 L after intravenous administration of 5 mg oxybutynin chloride. Both enantiomers of oxybutynin are highly bound (>99%) to plasma proteins. Both enantiomers of N-desethyloxybutynin are also highly bound (>97%) to plasma proteins. The major binding protein is alpha-1 acid glycoprotein.

Metabolism

Oxybutynin is metabolized primarily by the cytochrome P450 enzyme systems, particularly CYP3A4 found mostly in the liver and gut wall. Its metabolic products include phenylcyclohexylglycolic acid, which is pharmacologically inactive, and desethyloxybutynin, which is pharmacologically active. Following Oxybutynin chloride extended-release tablets administration, plasma concentrations of R- and S-desethyloxybutynin are 73% and 92%, respectively, of concentrations observed with oxybutynin.

Excretion

Oxybutynin is extensively metabolized by the liver, with less than 0.1% of the administered dose excreted unchanged in the urine. Also, less than 0.1% of the administered dose is excreted as the metabolite desethyloxybutynin.

Dose Proportionality

Pharmacokinetic parameters of oxybutynin and desethyloxybutynin (C _max and AUC) following administration of 5–20 mg of Oxybutynin chloride extended-release tablets are dose proportional.

Use in Specific Populations

Pediatric

The pharmacokinetics of Oxybutynin chloride extended-release tablets were evaluated in 19 children aged 5–15 years with detrusor overactivity associated with a neurological condition (e.g., spina bifida). The pharmacokinetics of Oxybutynin chloride extended-release tablets in these pediatric patients were consistent with those reported for adults (see Tables 2 and 3, and Figures 1 and 2 above).

Gender

There are no significant differences in the pharmacokinetics of oxybutynin in healthy male and female volunteers following administration of Oxybutynin chloride extended-release tablets.

Race

Available data suggest that there are no significant differences in the pharmacokinetics of oxybutynin based on race in healthy volunteers following administration of Oxybutynin chloride extended-release tablets.

13 Nonclinical Toxicology

13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility

A 24-month study in rats at dosages of oxybutynin chloride of 20, 80, and 160 mg/kg/day showed no evidence of carcinogenicity. These doses are approximately 6, 25, and 50 times the maximum human exposure, based on a human equivalent dose taking into account normalization of body surface area.

Oxybutynin chloride showed no increase of mutagenic activity when tested in Schizosaccharomyces pompholiciformis, Saccharomyces cerevisiae, and Salmonella typhimurium test systems.

Reproduction studies with oxybutynin chloride in the mouse, rat, hamster, and rabbit showed no evidence of impaired fertility.

14 Clinical Studies

Oxybutynin chloride extended-release tablets were evaluated for the treatment of patients with overactive bladder with symptoms of urge urinary incontinence, urgency, and frequency in three controlled efficacy studies. The majority of patients were Caucasian (89.0%) and female (91.9%) with a mean age of 59 years (range, 18 to 98 years). Entry criteria required that patients have urge or mixed incontinence (with a predominance of urge) as evidenced by ≥ 6 urge incontinence episodes per week and ≥ 10 micturitions per day. Study 1 was a fixed-dose escalation design, whereas the other two studies used a dose-adjustment design in which each patient's final dose was adjusted to a balance between improvement of incontinence symptoms and tolerability of side effects. All three studies included patients known to be responsive to oxybutynin or other anticholinergic medications, and these patients were maintained on a final dose for up to 2 weeks.

The efficacy results for the three controlled trials are presented in the following tables and figures.

Number of Urge Urinary Incontinence Episodes Per Week

Study 1	n	Oxybutynin chloride extended-release tablets	n	Placebo
Mean Baseline	34	15.9	16	20.9
Mean (SD) Change from Baseline Covariate adjusted mean with missing observations set to baseline values	34	-15.8 (8.9)	16	-7.6 (8.6)
95% Confidence Interval for Difference	(-13.6, -2.8) The difference between Oxybutynin chloride extended-release tabletsand placebo was statistically significant.
(Oxybutynin chloride extended-release tablets- Placebo)

Study 2	n	Oxybutynin chloride extended-release tablets	n	oxybutynin
Mean Baseline	53	27.6	52	23.0
Mean (SD) Change from Baseline Covariate adjusted mean with missing observations set to baseline values	53	-17.6 (11.9)	52	-19.4 (11.9)
95% Confidence Interval for Difference	(-2.8, 6.5)
(Oxybutynin chloride extended-release tablets- oxybutynin)

Study 3	n	Oxybutynin chloride extended-release tablets	n	oxybutynin
Mean Baseline	111	18.9	115	19.5
Mean (SD) Change from Baseline Covariate adjusted mean with missing observations set to baseline values	111	-14.5 (8.7)	115	-13.8 (8.6)
95% Confidence Interval for Difference	(-3.0, 1.6) The difference between Oxybutynin chloride extended-release tabletsand oxybutynin fulfilled the criteria for comparable efficacy.
(Oxybutynin chloride extended-release tablets- oxybutynin)

16 How Supplied/storage And Handling

Oxybutynin chloride extended-release tablets 5 mg are round, biconvex, white coated tablets imprinted in black ink with "270" on one side and "KU" on the other side.

They are supplied as follows:

NDC 50268-627-15 (10 Tablets per card, 5 cards per carton)

Oxybutynin chloride extended-release tablets 10 mg are round, biconvex, white coated tablets imprinted in black ink with "271" on one side and "KU" on the other side.

They are supplied as follows:

NDC 50268-628-15 (10 Tablets per card, 5 cards per carton)

Oxybutynin chloride extended-release tablets 15 mg are round, biconvex, white coated tablets imprinted in black ink with "272" on one side and "KU" on the other side.

They are supplied as follows:

NDC 50268-629-13 (10 Tablets per card, 3 cards per carton)

Dispensed in Unit Dose package. For Institutional Use Only.

16.1 Storage

Store at 25°C (77°F); excursions permitted to 15–30°C (59–86°F) [see USP Controlled Room Temperature]. Protect from moisture and humidity.

17 Patient Counseling Information

• Patients should be informed that oxybutynin may produce angioedema that could result in life threatening airway obstruction. Patients should be advised to promptly discontinue oxybutynin therapy and seek immediate medical attention if they experience swelling of the tongue, edema of the laryngopharynx, or difficulty breathing.
• Patients should be informed that anticholinergic (antimuscarinic) agents such as Oxybutynin chloride extended-release tablets, may produce clinically significant adverse reactions related to anticholinergic activity such as:
  • Urinary retention and constipation
  • Heat prostration due to decreased sweating. Heat prostration can occur when anticholinergic medicines are administered in the presence of high environmental temperature.
• Patients should be informed that anticholinergic medicines such as Oxybutynin chloride extended-release tablets may produce drowsiness (somnolence), dizziness or blurred vision. Patients should be advised to exercise caution in decisions to engage in potentially dangerous activities until Oxybutynin chloride extended-release tablets effects have been determined.
• Patients should be informed that alcohol may enhance the drowsiness caused by anticholinergic agents such as Oxybutynin chloride extended-release tablets.
• Patients should be informed that Oxybutynin chloride extended-release tablets should be swallowed whole with the aid of liquids. Patients should not chew, divide, or crush tablets. The medication is contained within a nonabsorbable shell designed to release the drug at a controlled rate. The tablet shell is eliminated from the body; patients should not be concerned if they occasionally notice in their stool something that looks like a tablet.
• Oxybutynin chloride extended-release tablets should be taken at approximately the same time each day.

For more information call 1-855-361-3993.

Manufactured for: AvKARE, Inc. Pulaski, TN 38478

Mfg. Rev. 10/16

AV Rev. 11/18 (P) AvPAK

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