Brand names: Ditropan, Ditropan XL, Oxytrol
Drug class: Antimuscarinics
VA class: GU201
CAS number: 1508-65-2

Medically reviewed by Drugs.com on Jul 24, 2023. Written by ASHP.

Introduction

Genitourinary antispasmodic agent; a synthetic tertiary amine antimuscarinic agent.^{100 116}

Uses for Oxybutynin

Overactive Bladder

Relief of symptoms of bladder instability associated with voiding (i.e., urgency, frequency, urinary leakage, urge incontinence, dysuria) in adults and pediatric patients > 5 years of age with uninhibited neurogenic or reflex neurogenic bladder (conventional tablets or oral solution).¹⁰⁰

Treatment of overactive bladder with symptoms of urge urinary incontinence, urgency, and frequency (extended-release tablets or transdermal system).^{116 119 120}

Relief of symptoms of detrusor overactivity associated with a neurological condition (e.g., spina bifida) in pediatric patients ≥ 6 years of age (extended-release tablets).¹¹⁶

Conventional tablets as effective as extended-release tablets.^{116 119}

Oxybutynin appears to be as effective as tolterodine (conventional tablets) in reducing urinary symptoms in patients with overactive bladder^{103 109} but is associated with a higher incidence of dry mouth.^{102 103 109 110 111}

Primary Nocturnal Enuresis† [off-label]

Has been used in children for the treatment of primary nocturnal enuresis^{† [off-label]}; however one study has determined that oxybutynin is not effective for management of primary nocturnal enuresis^{† [off-label]} in children with a history of nocturnal enuresis and normal bladders.¹⁰¹

Oxybutynin Dosage and Administration

General

• Discontinue therapy periodically to determine whether the patient can manage without the drug and to minimize any tendency for the patient to become resistant to the drug.^c

• Adjust dosage according to individual requirements and response.¹¹⁶

Administration

Administer orally^{100 116} or topically.¹²⁰

Oral Administration

Administer extended-release tablets without regard to meals.^{116 117 118}

Extended-release tablets should be swallowed intact with liquid, and should not be chewed, crushed, or broken.¹¹⁶

Administer extended-release tablets at approximately the same time each day.¹¹⁶

Topical Administration

After removal from protective pouch, apply transdermal system immediately to dry, intact skin on the abdomen, hip, or buttock.

A new application site should be selected with each new system; avoid reapplication to the same site within 7 days.¹²⁰

Used system should be discarded in a manner that prevents accidental application or ingestion by children, pets, or others.¹²⁰

Dosage

Conventional tablets, extended-release tablets, and oral solution available as oxybutynin chloride; dosage is expressed in terms of oxybutynin chloride.^{100 116}

Transdermal system available as oxybutynin; dosage is expressed in terms of oxybutynin.¹²⁰

Pediatric Patients

Overactive Bladder

Oral

Conventional tablets or oral solution: 5 mg twice daily for children ≥5 years of age.¹⁰⁰

Extended-release tablets: 5 mg once daily for children ≥6 years of age.¹¹⁶ Adjust dosage according to individual response and tolerance;¹¹⁶ increase dosage at 7-day intervals in increments of 5 mg¹¹⁶ up to maximum dosage of 20 mg once daily.¹¹⁶

Adults

Overactive Bladder

Oral

Conventional tablets or oral solution: 5 mg 2–3 times daily.¹⁰⁰

Extended-release tablets: 5 or 10 mg once daily.¹¹⁶ Adjust daily dosage according to individual response and tolerance;¹¹⁶ increase dosage at 7-day intervals in increments of 5 mg¹¹⁶ up to maximum dosage of 30 mg once daily.¹¹⁶

Topical

1 transdermal system (delivering 3.9 mg per day) twice weekly (every 3–4 days).¹²⁰

Prescribing Limits

Pediatric Patients

Overactive Bladder

Oral

Conventional tablets or oral solution: Maximum 5 mg 3 times daily.¹⁰⁰

Extended-release tablets: Maximum 20 mg once daily.¹¹⁶

Adults

Overactive Bladder

Oral

Conventional tablets or oral solution: Maximum 5 mg 4 times daily.¹⁰⁰

Extended-release tablets: Maximum 30 mg once daily.¹¹⁶

Special Populations

Geriatric Patients

A lower initial dosage (2.5 mg 2 or 3 times daily) of conventional tablets or oral solution is recommended for frail geriatric patients.¹⁰⁰ (See Geriatric Use under Cautions.)

Cautions for Oxybutynin

Contraindications

Conventional Tablets and Oral Solution

• Patients with untreated angle-closure glaucoma or those with untreated narrow anterior chamber angles.¹⁰⁰

• Obstructive uropathy.¹⁰⁰

• Partial or complete obstruction of the GI tract, paralytic ileus, intestinal atony (in elderly or debilitated patients), megacolon, toxic megacolon complicating ulcerative colitis, or severe colitis.¹⁰⁰

• Myasthenia gravis.¹⁰⁰

• Unstable cardiovascular status in acute hemorrhage.¹⁰⁰

• Known hypersensitivity to oxybutynin or any ingredient in the formulations.

Extended-release Tablets and Transdermal System

• Presence or risk of urinary retention.^{116 120}

• Presence or risk of gastric retention and other severe decreased GI motility conditions.^{116 120}

• Presence or risk of uncontrolled angle-closure glaucoma.^{116 120}

• Known hypersensitivity to oxybutynin or any ingredient in the formulations.^{100 116}

Warnings/Precautions

Warnings

Risk of heat prostration (i.e., fever and heat stroke due to decreased sweating) when administered during hot weather.^{100 116 120}

Diarrhea may be a symptom of partial intestinal obstruction, especially in patients with ileostomies or colostomies; in this instance, treatment with oxybutynin would be inappropriate and possibly harmful.¹⁰⁰

General Precautions

Urinary Retention

Risk of urinary retention; use with caution in patients with clinically important bladder outflow obstruction.^{116 120}

GI Effects

Risk of gastric retention; use with caution in patients with GI obstructive disorders.^{116 120}

Risk of decreased GI motility; use with caution in patients with conditions such as ulcerative colitis or intestinal atony.^{116 120} Use in patients with ulcerative colitis may suppress intestinal motility, resulting in paralytic ileus and precipitating or exacerbating toxic megacolon.¹⁰⁰

Use with caution in patients who have gastroesophageal reflux (GERD) and/or in those who are concurrently receiving drugs that can cause or exacerbate esophagitis (e.g., bisphosphonates).^{116 120} (See Specific Drugs under Interactions.)

As with other nondeformable material, extended-release tablets should be used with caution in patients with preexisting severe GI narrowing (pathologic or iatrogenic) since obstruction may occur.¹¹⁶

Myasthenia Gravis

Oxybutynin may increase risk of aggravating symptoms of myasthenia gravis.¹¹⁶ Use with caution in patients with myasthenia gravis.^{116 120}

Other Concomitant Diseases

Use with caution in patients with autonomic neuropathy.¹⁰⁰ Use of oxybutynin may exacerbate manifestations of hyperthyroidism, CHD, CHF, cardiac arrhythmias, hiatal hernia, tachycardia, hypertension, and prostatic hypertrophy.¹⁰⁰

Specific Populations

Pregnancy

Category B.^{100 116 120}

Lactation

Not known whether distributed into milk.^{100 116 120} Caution if used in nursing women.^{100 116 120}

Pediatric Use

Safety and efficacy of conventional tablets and oral solution not established in children <5 years of age; use in these children not recommended.¹⁰⁰

Safety and efficacy of extended-release tablets not established in children <6 years of age.¹¹⁶ Use of this preparation not recommended in children who cannot swallow the tablet whole without chewing, dividing, or crushing.¹¹⁶

Safety and efficacy of transdermal system not established in pediatric patients.¹²⁰

Geriatric Use

No substantial differences in safety and efficacy relative to younger adults,^{116 120} but increased sensitivity cannot be ruled out.¹²⁰ Use with caution in frail geriatric patients.¹⁰⁰

Renal or Hepatic Impairment

Not studied in patients with renal or hepatic impairment; use with caution.^{116 120}

Common Adverse Effects

Conventional or extended-release tablets or oral solution: dry mouth, dizziness, constipation, somnolence, impaired urination, nausea, blurred vision, dyspepsia, asthenia, pain, abdominal pain, headache, rhinitis, dry eyes, diarrhea, increased post-void residual volume, urinary tract infection.¹⁰⁰

Transdermal system: application site reactions (e.g., pruritus, erythema, rash, vesicles, macules), dry mouth, constipation, diarrhea, abnormal vision, dysuria.¹²⁰

Drug Interactions

Metabolized principally by CYP3A4.^{116 120}

No formal drug interaction studies have been performed with transdermal system.¹²⁰

Drugs Affecting Hepatic Microsomal Enzymes

Inhibitors of CYP3A4: Potential pharmacokinetic interaction (increased oxybutynin concentrations).¹¹⁶

Drugs Affected by GI Motility

Potential pharmacokinetic interaction (altered absorption because of decreased GI motility).¹¹⁶

Specific Drugs

Oxybutynin Pharmacokinetics

Absorption

Bioavailability

Rapidly absorbed following oral administration (conventional tablets or oral solution); ¹⁰⁰ undergoes extensive first-pass metabolism.¹²⁰ Absolute bioavailability of oxybutynin is approximately 6%.¹²⁰

Following oral administration of extended-release tablets, relative bioavailabilities of R- and S-oxybutynin are 156 and 187% respectively, compared with conventional oxybutynin formulations.^{116 119}

Absorption of oxybutynin is bioequivalent when the transdermal system is applied to the abdomen, buttocks, or hip.¹²⁰

Duration

Following oral administration (conventional tablets or oral solution), peak plasma concentrations are achieved within 1 hour.¹⁰⁰

Following oral administration of extended-release tablets, plasma oxybutynin concentrations increase gradually for 4–6 hours, peak within 12–13 hours, and are maintained for up to 24 hours.^{116 119} Steady-state concentrations are achieved by the third day.¹¹⁶ In pediatric patients 5–15 years of age, peak plasma concentrations are achieved within approximately 5 hours.¹¹⁶

Following application of the transdermal system, oxybutynin plasma concentrations increase for approximately 24–48 hours, peak within 36–48 hours, and are maintained for up to 96 hours.¹²⁰ Following multiple applications of the transdermal system, peak plasma concentrations are achieved within 10–28 hours.¹²⁰ Steady-state concentrations are achieved with application of the second transdermal system.¹²⁰

Food

Food may delay absorption and increase bioavailability of oxybutynin oral solution by 25%.¹⁰⁰ Food does not appear to affect absorption of extended-release tablets.^{116 117 118}

Distribution

Extent

Distributed in the brain, lungs, kidneys, and liver following oral administration in rats.^c

Not known whether oxybutynin is distributed into milk in humans.^{100 116 120}

Elimination

Metabolism

Metabolized to active (desethyloxybutynin) and inactive (phenylcyclohexylglycolic acid) metabolites^{116 119 120} principally via CYP3A4, which is found mainly in the liver and intestinal wall.^{116 120}

Elimination Route

Excreted principally in urine as metabolites; <0.1% excreted as unchanged drug^{116 120 120} and <0.1% excreted as desethyloxybutynin.^{100 116 120}

Half-life

Conventional tablets or oral solution: 2–3 hours¹⁰⁰

Extended-release tablets: 13.2 and 12.4 hours for the R- and S-isomers of oxybutynin, respectively.¹¹⁶

Approximately 7–8 hours following removal of transdermal system.¹²⁰

Special Populations

Not studied in patients with renal or hepatic impairment.^{116 120}

Increased elimination half-life in frail geriatric patients.¹⁰⁰

Decreased metabolism in healthy Japanese individuals compared with Caucasians.¹²⁰

Stability

Storage

Oral

Conventional Tablets and Oral Solution

Tight, light resistant containers at 15–30°C .¹⁰⁰

Extended-release Tablets

25°C (may be exposed to 15–30°C).¹¹⁶ Protect from moisture and humidity.¹¹⁶

Transdermal System

25°C (may be exposed to 15–30°C).¹²⁰ Protect from moisture and humidity.¹²⁰ Do not store outside sealed pouch.¹²⁰

Actions

• Racemic mixture of R- and S-isomers.¹²⁰ Antimuscarinic activity resides predominantly in the R-isomer.^{116 120} Free base (oxybutynin) pharmacologically equivalent to oxybutynin chloride.¹²⁰

• Chemically and pharmacologically similar to some anticholinergic, antispasmodic, local anesthetic, and antihistaminic compounds.^c

• Exerts a direct spasmolytic action and inhibits the muscarinic action of acetylcholine on smooth muscle.^{100 116}

• Acts as a competitive antagonist of acetylcholine at postganglionic muscarinic receptors,¹²⁰ resulting in relaxation of bladder smooth muscle.^{100 116 120} In patients with uninhibited neurogenic and reflex neurogenic bladders, oxybutynin diminishes the frequency of uninhibited contractions of the detrusor muscle and delays the initial desire to void, resulting in decreased urgency and the frequency of incontinent episodes and voluntary urination.^{100 116 120}

• Does not appear to exhibit antinicotinic effects (i.e., block acetylcholine effects at skeletal myoneural junctions or at autonomic ganglia).^{100 116}

• Risk of heat prostration (i.e., fever and heat stroke due to decreased sweating) when administered during hot weather.^{100 116 120}

• Risk of blurred vision, drowsiness, or somnolence;^{100 116 120} importance of exercising caution when driving or operating machinery.¹⁰⁰ Alcohol or other sedative drugs may enhance drowsiness caused by oxybutynin.^{100 116 120}

• When dispensing extended-release tablets, advise patients not to become alarmed if they notice a tablet-like substance in their stools; this is normal since the tablet containing the drug is designed to remain intact and slowly release the drug from a nonabsorbable shell during passage through the GI tract.¹¹⁶

• When dispensing the transdermal system, provide patients with a copy of manufacturer’s patient information.¹²⁰

• Importance of informing clinicians of existing or contemplated therapy, including prescription and OTC drugs and herbal supplements, as well as any concomitant illnesses (e.g., cardiovascular disease).^{100 116 120}

• Importance of women informing their clinician if they are or plan to become pregnant or plan to breast-feed.^{100 116 120}

• Importance of informing patients of other important precautionary information. (See Cautions.)

Preparations

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

* available from one or more manufacturer, distributor, and/or repackager by generic (nonproprietary) name

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