Detrusitol SR: Uses, Dosage & Side Effects
An antimuscarinic extended-release capsule for the treatment of overactive bladder with symptoms of urinary urgency, frequency, and urge incontinence
Detrusitol SR (tolterodine tartrate extended-release) is a prescription antimuscarinic medication used to treat overactive bladder (OAB) with symptoms of urinary urgency, urinary frequency, and urge urinary incontinence. It works by blocking muscarinic receptors on the detrusor muscle of the bladder, reducing involuntary bladder contractions and increasing functional bladder capacity. The extended-release formulation is taken once daily and provides steady drug levels over 24 hours, resulting in improved tolerability compared to immediate-release tolterodine. Clinical trials have demonstrated that Detrusitol SR significantly reduces the number of urge incontinence episodes, micturitions per day, and urgency episodes, while improving patients' quality of life. Dry mouth, the most common anticholinergic side effect, occurs less frequently with the extended-release formulation.
Quick Facts: Detrusitol SR
Key Takeaways
- Detrusitol SR (tolterodine tartrate extended-release) is a once-daily antimuscarinic medication specifically designed for the treatment of overactive bladder (OAB) with symptoms of urgency, frequency, and urge urinary incontinence.
- The extended-release formulation provides steady plasma levels over 24 hours, resulting in significantly less dry mouth compared to the immediate-release version while maintaining equivalent clinical efficacy.
- Clinical trials demonstrated that Detrusitol SR reduces urge incontinence episodes by approximately 71% and decreases urinary frequency by an average of 1.8 voids per day compared to baseline.
- Detrusitol SR should be used with caution in patients with urinary retention, gastric retention, uncontrolled narrow-angle glaucoma, myasthenia gravis, or severe hepatic impairment, and the dose should be reduced to 2 mg daily when co-administered with strong CYP3A4 inhibitors.
- Available in 2 mg and 4 mg extended-release hard capsules; the recommended starting dose for most adults is 4 mg once daily, taken with water, with or without food, and the capsule must be swallowed whole without crushing or chewing.
What Is Detrusitol SR and What Is It Used For?
Detrusitol SR contains the active substance tolterodine tartrate, a competitive muscarinic receptor antagonist that belongs to the class of medications known as antimuscarinics or anticholinergics. Tolterodine was specifically developed for the treatment of overactive bladder, making it one of the first antimuscarinic agents designed with bladder selectivity in mind. Unlike older anticholinergic drugs that were repurposed for urological conditions, tolterodine was synthesized and optimized to preferentially target the bladder over other organs, particularly the salivary glands, which is responsible for the reduced incidence of dry mouth compared to non-selective antimuscarinics.
Overactive bladder (OAB) is a common clinical syndrome defined by the International Continence Society (ICS) as urinary urgency, usually accompanied by increased urinary frequency and nocturia (waking at night to urinate), with or without urge urinary incontinence, in the absence of urinary tract infection or other obvious pathology. OAB affects an estimated 12–17% of the adult population worldwide, with prevalence increasing significantly with age. Both men and women are affected, though the symptom profile may differ between sexes. OAB can have a profound impact on quality of life, affecting work productivity, social interactions, sleep quality, sexual function, and mental health. Many patients with OAB experience embarrassment, social isolation, and depression, yet a substantial proportion never seek medical help due to stigma or the misconception that urinary symptoms are a normal part of aging.
The pathophysiology of OAB involves involuntary contractions of the detrusor muscle during the filling phase of the micturition cycle. Under normal circumstances, the detrusor muscle remains relaxed during bladder filling while the internal urethral sphincter maintains continence. When the bladder reaches its capacity and the individual chooses to void, the detrusor contracts under voluntary control mediated by parasympathetic cholinergic nerves. In OAB, however, the detrusor muscle contracts involuntarily before the bladder is full, generating a sudden, intense urge to urinate that may be difficult to suppress. These involuntary contractions are primarily mediated by acetylcholine acting on muscarinic receptors (predominantly M2 and M3 subtypes) on the detrusor smooth muscle. The M3 receptor subtype, although less abundant than M2 in the bladder, is the primary mediator of detrusor contraction.
Tolterodine works by competitively blocking acetylcholine from binding to muscarinic receptors on the detrusor muscle. This reduces the frequency and amplitude of involuntary detrusor contractions, increases the volume at which the first involuntary contraction occurs, and ultimately increases functional bladder capacity. The net clinical effect is a reduction in urgency episodes, fewer voids per day, fewer incontinence episodes, and an increased volume of urine voided per micturition. Tolterodine and its equipotent active metabolite, 5-hydroxymethyl tolterodine (DD01), both contribute to the pharmacological effect. Importantly, tolterodine demonstrates functional selectivity for the bladder over the salivary glands in vivo, which means that at therapeutic doses, it inhibits bladder contractions more effectively than it inhibits salivary secretion, resulting in a more favorable tolerability profile.
The “SR” (sustained-release) or extended-release formulation of tolterodine was developed to address some limitations of the original immediate-release tablet. The extended-release capsule uses a proprietary bead technology that releases tolterodine gradually throughout the gastrointestinal tract over approximately 24 hours. This produces a smoother pharmacokinetic profile with lower peak plasma concentrations (Cmax) and more consistent trough concentrations compared to the immediate-release formulation. The clinical consequence of this smoother profile is a significant reduction in the incidence of dry mouth (the most common reason patients discontinue antimuscarinic therapy) while maintaining comparable or superior efficacy in reducing OAB symptoms.
Detrusitol SR was evaluated in several pivotal clinical trials. The ACET (Antimuscarinic Clinical Effectiveness Trial) study, a large randomized, double-blind, active-controlled trial, demonstrated that tolterodine extended-release 4 mg once daily produced a significantly greater reduction in urge incontinence episodes compared to immediate-release tolterodine 2 mg twice daily, while also producing a substantially lower rate of dry mouth (23% vs 30%). In the pivotal registration trials, tolterodine ER reduced the mean number of urge incontinence episodes per week by approximately 71% from baseline (compared to 33% for placebo), and reduced the mean number of micturitions per 24 hours by 1.8 (compared to 1.2 for placebo). These results were consistent across age groups, sexes, and baseline severity levels.
Overactive bladder is a clinical syndrome, not a disease. It is defined by symptoms — urgency (the hallmark symptom), often accompanied by frequency (voiding 8 or more times per day), nocturia (waking to void at night), and with or without urge incontinence. OAB affects approximately 12–17% of adults worldwide. It is not a normal part of aging and is treatable. If you experience these symptoms, consult your healthcare provider. Behavioral therapies (bladder training, pelvic floor exercises) are typically recommended as first-line treatment, with antimuscarinic medications like Detrusitol SR used as second-line pharmacological therapy.
What Should You Know Before Taking Detrusitol SR?
Contraindications
Detrusitol SR is contraindicated (must not be used) in several specific clinical situations. The primary contraindications reflect the anticholinergic mechanism of action and the potential for the drug to worsen pre-existing conditions where muscarinic receptor blockade would be harmful.
- Hypersensitivity: Do not use Detrusitol SR if you are allergic to tolterodine tartrate, fesoterodine (which is metabolized to the same active metabolite), or any of the excipients in the formulation. Allergic reactions, while uncommon, can include skin rash, urticaria, and angioedema.
- Urinary retention: Because antimuscarinics reduce detrusor contractility, they can worsen urinary retention in patients who already have significant difficulty emptying their bladder. Patients with clinically significant bladder outflow obstruction at risk of urinary retention should not use Detrusitol SR.
- Gastric retention: Anticholinergic agents reduce gastrointestinal motility. Patients with gastric retention or conditions predisposing to gastric retention (such as severe gastroparesis) should not use Detrusitol SR.
- Uncontrolled narrow-angle glaucoma: Muscarinic receptor blockade can precipitate acute angle-closure glaucoma by dilating the pupil (mydriasis) and thickening the lens, which pushes the iris forward and obstructs the drainage angle. Patients with uncontrolled narrow-angle glaucoma must not use Detrusitol SR. Patients with open-angle glaucoma are generally not at increased risk.
- Myasthenia gravis: Anticholinergic medications can potentially worsen muscle weakness in patients with myasthenia gravis, an autoimmune neuromuscular disorder. Detrusitol SR is contraindicated in patients with this condition.
- Severe ulcerative colitis and toxic megacolon: Anticholinergic agents can reduce intestinal motility and are contraindicated in patients with these serious gastrointestinal conditions.
Warnings and Precautions
Anticholinergic medications including Detrusitol SR may cause or worsen constipation, dry mouth, blurred vision, and cognitive impairment, particularly in elderly patients. Use the lowest effective dose and monitor regularly. If you experience difficulty urinating, severe constipation, or eye pain, contact your doctor immediately.
Before starting Detrusitol SR, discuss the following considerations with your healthcare provider:
- Bladder outflow obstruction: In patients with conditions such as benign prostatic hyperplasia (BPH) that cause partial bladder outflow obstruction, Detrusitol SR should be used with caution and under close monitoring. The reduction in detrusor contractility may lead to incomplete bladder emptying and, in severe cases, urinary retention. Your doctor may want to measure your post-void residual volume before and during treatment.
- Gastrointestinal obstructive disorders: Tolterodine should be used with caution in patients with conditions that slow gastrointestinal transit, such as pyloric stenosis, as anticholinergic effects can further reduce motility and worsen symptoms.
- Hepatic impairment: Tolterodine is extensively metabolized in the liver. In patients with mild to moderate hepatic impairment (Child-Pugh Class A or B), the dose should be reduced to 2 mg once daily. Detrusitol SR is not recommended in patients with severe hepatic impairment (Child-Pugh Class C) due to insufficient data.
- Renal impairment: In patients with severe renal impairment (GFR < 30 mL/min), a dose reduction to 2 mg once daily is recommended. The drug should be used with caution due to increased plasma exposure.
- QT prolongation: Post-marketing surveillance has identified rare cases of QT prolongation associated with tolterodine. Patients with known QT prolongation, those taking medications that prolong the QT interval, or those with relevant pre-existing cardiac conditions (congenital long QT syndrome, heart failure, electrolyte disturbances including hypokalemia, hypomagnesemia, or hypocalcemia) should be monitored with particular care. The risk of QT prolongation is increased at supratherapeutic doses.
- Cognitive effects in the elderly: Anticholinergic medications can cause or exacerbate cognitive impairment, confusion, and hallucinations, particularly in elderly patients. Long-term use of anticholinergic drugs has been associated with an increased risk of dementia in observational studies, although a direct causal relationship has not been definitively established. The lowest effective dose should be used, and treatment should be re-evaluated regularly in elderly patients.
- Angioedema: Rare cases of angioedema have been reported with tolterodine. If angioedema occurs, treatment should be discontinued immediately and appropriate therapy should be initiated. Tolterodine should not be re-administered.
Pregnancy and Breastfeeding
There are no adequate and well-controlled studies of tolterodine in pregnant women. Animal reproductive toxicity studies have shown reduced fetal body weight and an increased incidence of fetal anomalies at doses associated with maternal toxicity, but not at clinically relevant doses. Nevertheless, as a precaution, Detrusitol SR should not be used during pregnancy unless the potential benefit to the mother clearly outweighs the potential risk to the fetus. Women of childbearing potential should be advised to use effective contraception during treatment.
It is not known whether tolterodine or its metabolites are excreted in human breast milk. Studies in mice have shown that tolterodine and its metabolites are secreted into milk. Because many drugs are excreted in human milk and because of the potential for adverse effects on the nursing infant (dry mouth, constipation, urinary retention), breastfeeding is not recommended during treatment with Detrusitol SR. A decision should be made whether to discontinue breastfeeding or to discontinue the drug, taking into account the importance of the drug to the mother.
Driving and Operating Machinery
Detrusitol SR may cause blurred vision, dizziness, and drowsiness in some patients. These effects can impair the ability to drive and operate machinery. Patients should be advised to exercise caution when driving or performing other tasks requiring alertness, fine motor coordination, or clear vision until they know how Detrusitol SR affects them. If you experience visual disturbances or dizziness, avoid driving and operating machinery.
Children and Adolescents
The safety and efficacy of Detrusitol SR have not been established in children and adolescents under 18 years of age. The extended-release formulation is not recommended for use in pediatric patients. Overactive bladder in children may have different underlying causes compared to adults and typically requires different treatment approaches, including behavioral interventions and, when necessary, different pharmacological agents.
How Does Detrusitol SR Interact with Other Drugs?
Tolterodine is metabolized primarily by two cytochrome P450 enzymes: CYP2D6 (the major metabolic pathway) and CYP3A4 (an alternative pathway). Approximately 7% of the Caucasian population and 1–2% of the Asian population are CYP2D6 poor metabolizers, meaning they lack functional CYP2D6 enzyme activity. In these individuals, CYP3A4 becomes the dominant metabolic pathway, and interactions with CYP3A4 inhibitors become clinically more significant. Understanding these metabolic pathways is essential for predicting and managing drug interactions with Detrusitol SR.
The following table summarizes the most clinically relevant drug interactions with Detrusitol SR:
| Interacting Drug/Class | Mechanism | Clinical Effect | Recommendation |
|---|---|---|---|
| Ketoconazole, Itraconazole | Strong CYP3A4 inhibition | Increased tolterodine plasma levels (up to 2-fold increase in AUC) | Reduce dose to 2 mg once daily |
| Clarithromycin, Erythromycin | Moderate CYP3A4 inhibition | Moderately increased tolterodine levels | Consider dose reduction; monitor for side effects |
| Fluoxetine, Paroxetine | CYP2D6 inhibition | Increased tolterodine levels in CYP2D6 extensive metabolizers (shift to poor metabolizer phenotype) | No dose adjustment typically required (total active moiety unchanged); monitor for anticholinergic effects |
| Rifampicin, Carbamazepine, Phenytoin | CYP3A4 induction | Decreased tolterodine levels; reduced efficacy | May need higher dose or alternative therapy |
| Other anticholinergics (e.g., oxybutynin, solifenacin, tiotropium) | Additive pharmacodynamic effect | Increased risk of dry mouth, constipation, urinary retention, cognitive impairment | Avoid combination; use one anticholinergic at a time |
| QT-prolonging drugs (e.g., amiodarone, sotalol, haloperidol, methadone) | Additive QT prolongation | Increased risk of cardiac arrhythmias (torsades de pointes) | Use with caution; ECG monitoring recommended |
| Cholinesterase inhibitors (e.g., donepezil, rivastigmine) | Opposing pharmacodynamic effect | Reduced efficacy of both drugs; anticholinergics may reduce effectiveness of dementia treatment | Avoid combination when possible; consider mirabegron as alternative for OAB |
| Metoclopramide, Domperidone | Opposing effects on GI motility | Reduced prokinetic effect; both drugs partially antagonized | Monitor GI symptoms; consider alternative approaches |
Important Interaction Considerations
The interaction between Detrusitol SR and CYP3A4 inhibitors deserves special attention. In a pharmacokinetic study, co-administration of ketoconazole 200 mg once daily with tolterodine 4 mg twice daily (immediate-release) resulted in a 2-fold increase in the area under the plasma concentration-time curve (AUC) of tolterodine. For this reason, in patients who are receiving potent CYP3A4 inhibitors (ketoconazole, itraconazole, ritonavir, nelfinavir), the recommended dose of Detrusitol SR should not exceed 2 mg once daily. Similarly, grapefruit juice is a moderate CYP3A4 inhibitor and may increase tolterodine levels; patients should be advised to avoid large quantities of grapefruit juice during treatment.
The interaction with CYP2D6 inhibitors is more nuanced. When CYP2D6 is inhibited, the metabolism of tolterodine shifts to the CYP3A4 pathway, producing less of the active 5-hydroxymethyl metabolite (DD01) but higher levels of the parent compound. Because the parent compound and its active metabolite have similar pharmacological activity, the total exposure to active moieties remains relatively constant, and dose adjustment is generally not required for CYP2D6 inhibitors alone. However, when both CYP2D6 and CYP3A4 inhibitors are used concurrently, the effect on tolterodine exposure can be substantially greater, and such combinations should be avoided or used with careful dose reduction.
Perhaps the most clinically important pharmacodynamic interaction is between Detrusitol SR and cholinesterase inhibitors such as donepezil and rivastigmine, which are commonly used in Alzheimer's disease and other forms of dementia. These drugs work by increasing acetylcholine levels at the synapse, while tolterodine blocks acetylcholine receptors. The combination results in pharmacological antagonism, potentially reducing the effectiveness of both treatments. Given the association between long-term anticholinergic use and cognitive decline in elderly patients, this combination should be avoided whenever possible. Alternative OAB treatments that do not have anticholinergic properties, such as mirabegron (a beta-3 adrenergic agonist), should be considered in patients taking cholinesterase inhibitors.
What Is the Correct Dosage of Detrusitol SR?
Adults
Standard Adult Dosage
The recommended dose is 4 mg once daily, taken orally with water. The capsule can be taken with or without food. If the 4 mg dose is not well tolerated, particularly due to anticholinergic side effects such as dry mouth, the dose may be reduced to 2 mg once daily. The extended-release capsule must be swallowed whole and must not be crushed, chewed, or opened, as this would destroy the extended-release mechanism and result in rapid absorption of the entire dose.
Treatment response should be evaluated after approximately 4–8 weeks. If the initial dose does not provide adequate symptom relief after 8 weeks and is well tolerated, the prescriber should consider whether a dose adjustment or alternative treatment is appropriate. Behavioral therapies (bladder training, timed voiding, pelvic floor muscle exercises) should be continued alongside pharmacological treatment, as the combination of behavioral and pharmacological approaches often produces better outcomes than either approach alone.
Elderly Patients
Elderly Dosage
No specific dose adjustment is required based on age alone. However, elderly patients are more susceptible to anticholinergic side effects including dry mouth, constipation, blurred vision, and particularly cognitive impairment. It is prudent to start with the lower dose of 2 mg once daily in frail elderly patients and to titrate up to 4 mg only if needed and well tolerated. Regular review is recommended to assess ongoing benefit and monitor for cognitive changes.
Hepatic and Renal Impairment
Dose Adjustment for Hepatic/Renal Impairment
Hepatic impairment (mild to moderate, Child-Pugh A/B): Reduce dose to 2 mg once daily. Severe hepatic impairment (Child-Pugh C): Not recommended due to insufficient data.
Severe renal impairment (GFR < 30 mL/min): Reduce dose to 2 mg once daily. Mild to moderate renal impairment does not require dose adjustment.
Children
Detrusitol SR is not recommended for use in children and adolescents under 18 years of age. The safety and efficacy of the extended-release formulation have not been established in this population. Pediatric overactive bladder requires specialized assessment and management approaches.
Missed Dose
If you miss a dose of Detrusitol SR, take it as soon as you remember. However, if it is almost time for your next dose (within approximately 12 hours), skip the missed dose and take your next dose at the regular scheduled time. Do not take a double dose to make up for a missed dose. Taking two doses too close together increases the risk of anticholinergic side effects without providing additional therapeutic benefit.
Overdose
In case of suspected overdose, seek immediate medical attention. Symptoms of tolterodine overdose may include severe anticholinergic effects: significantly dilated pupils, severe dry mouth, rapid heartbeat (tachycardia), urinary retention, agitation, hallucinations, convulsions, and in severe cases, respiratory failure and QT prolongation with potential cardiac arrhythmias.
There is no specific antidote for tolterodine overdose. Treatment is supportive and symptomatic. In cases of severe anticholinergic toxicity, physostigmine (a cholinesterase inhibitor that crosses the blood-brain barrier) may be considered under specialist supervision, particularly if central nervous system symptoms such as agitation, hallucinations, or seizures are prominent. Gastric lavage or activated charcoal may be considered if the overdose is detected early. ECG monitoring is recommended due to the risk of QT prolongation. The extended-release formulation may continue to release tolterodine for several hours after ingestion, so prolonged monitoring is warranted.
The maximum single overdose of tolterodine reported in clinical experience was 12.8 mg of the immediate-release formulation. Symptoms included mydriasis and difficulty with accommodation. In clinical trials, doses of up to 12 mg per day (3 times the therapeutic dose of the ER formulation) were administered to healthy volunteers, with the primary effects being anticholinergic symptoms including dry mouth and impaired accommodation. QTc prolongation was observed at supratherapeutic doses.
| Patient Group | Recommended Dose | Maximum Dose | Notes |
|---|---|---|---|
| Adults (standard) | 4 mg once daily | 4 mg/day | Can reduce to 2 mg if side effects occur |
| Elderly (frail) | 2 mg once daily | 4 mg/day | Start low; monitor cognition; review regularly |
| Hepatic impairment (mild/moderate) | 2 mg once daily | 2 mg/day | Severe impairment: not recommended |
| Severe renal impairment | 2 mg once daily | 2 mg/day | GFR < 30 mL/min |
| With CYP3A4 inhibitors | 2 mg once daily | 2 mg/day | E.g., ketoconazole, itraconazole, ritonavir |
| Children (<18 years) | Not recommended | N/A | Safety and efficacy not established |
What Are the Side Effects of Detrusitol SR?
Like all medicines, Detrusitol SR can cause side effects, although not everybody gets them. Most side effects are related to the anticholinergic (antimuscarinic) mechanism of action and are dose-dependent. The extended-release formulation was specifically developed to reduce peak plasma concentrations and thus minimize the severity of anticholinergic side effects, particularly dry mouth. In clinical trials, the overall incidence of adverse events leading to treatment discontinuation was similar between Detrusitol SR and placebo (approximately 5–7%), indicating a generally good tolerability profile.
The following side effect frequencies are based on data from clinical trials and post-marketing surveillance. Side effects are classified according to the frequency convention used by the European Medicines Agency:
Very Common
Affects more than 1 in 10 patients (>10%)
- Dry mouth (xerostomia) — the most frequently reported side effect, affecting approximately 23% of patients on the 4 mg dose (vs. 8% on placebo); typically mild to moderate in severity and often improves with continued use
Common
Affects 1 to 10 in 100 patients (1–10%)
- Headache
- Dizziness
- Drowsiness (somnolence)
- Constipation
- Abdominal pain
- Dyspepsia (indigestion)
- Dry eyes
- Blurred vision (abnormal accommodation)
- Fatigue
- Urinary tract infection
Uncommon
Affects 1 to 10 in 1,000 patients (0.1–1%)
- Urinary retention
- Gastro-oesophageal reflux disease
- Flatulence
- Palpitations
- Tachycardia (rapid heartbeat)
- Peripheral oedema
- Dry skin
- Nervousness
- Paraesthesia (tingling/numbness)
- Weight gain
- Chest pain
Rare
Affects 1 to 10 in 10,000 patients (0.01–0.1%)
- Confusion and disorientation
- Hallucinations
- Memory impairment
- Angioedema (swelling of face, lips, tongue, or throat)
- Anaphylactoid reactions
- Severe skin reactions
Not Known
Frequency cannot be estimated from available data
- QT prolongation (observed at supratherapeutic doses)
- Torsades de pointes (very rare cardiac arrhythmia)
- Exacerbation of dementia symptoms in elderly patients
- Worsening of gastro-oesophageal reflux
Managing Common Side Effects
Dry mouth is the most common reason patients discontinue antimuscarinic therapy for OAB. Several strategies can help manage this side effect: frequent sips of water throughout the day, sugar-free chewing gum or lozenges to stimulate saliva production, saliva substitutes for severe cases, avoiding caffeinated and alcoholic beverages which worsen dehydration, and maintaining good oral hygiene to prevent dental caries (a risk associated with chronic dry mouth). If dry mouth remains intolerable at the 4 mg dose, reducing to 2 mg once daily often provides meaningful relief while still maintaining a clinically significant effect on OAB symptoms.
Constipation can be managed with increased fluid intake, dietary fiber, regular physical activity, and, if necessary, a mild osmotic laxative such as macrogol (polyethylene glycol). Blurred vision is typically related to impaired accommodation (difficulty focusing on near objects) and tends to be more noticeable in the first weeks of treatment. If blurred vision persists, an ophthalmological evaluation may be warranted. Dizziness and drowsiness, if present, are usually mild and tend to diminish with continued use. Patients should avoid driving or operating machinery until they know how Detrusitol SR affects them.
Seek medical attention if you experience: difficulty urinating or inability to urinate (urinary retention), severe constipation or abdominal pain, rapid or irregular heartbeat, eye pain or sudden visual changes (possible acute angle-closure glaucoma), swelling of the face, lips, tongue, or throat (angioedema), or confusion, hallucinations, or significant cognitive changes. These may indicate serious adverse effects requiring immediate evaluation.
How Should You Store Detrusitol SR?
Proper storage of Detrusitol SR is essential to maintain the medication's stability and effectiveness throughout its shelf life. The extended-release capsules should be stored at room temperature, not exceeding 25°C (77°F). Brief exposures to temperatures up to 30°C (86°F) are generally acceptable during transport or temporary storage, but prolonged exposure to elevated temperatures should be avoided as it may affect the integrity of the extended-release mechanism.
The capsules should be kept in their original blister packaging until the time of administration to protect them from moisture. Moisture exposure can compromise the extended-release coating, potentially altering the drug release profile and affecting both efficacy and tolerability. Do not transfer the capsules to pill organizers or other containers that do not provide adequate moisture protection for extended periods.
Do not use Detrusitol SR after the expiry date stated on the carton and blister packaging. The expiry date refers to the last day of that month. Keep all medicines out of the sight and reach of children. Do not dispose of medications via wastewater or household waste. Ask your pharmacist about proper disposal methods. These measures help protect the environment and prevent accidental ingestion.
What Does Detrusitol SR Contain?
Each Detrusitol SR extended-release hard capsule contains the following:
Active Ingredient
Tolterodine tartrate: Available in two strengths — 2 mg and 4 mg per capsule. Tolterodine tartrate is a white crystalline powder with the chemical name (R)-2-[3-(diisopropylamino)-1-phenylpropyl]-4-methylphenol L-(+)-hydrogen tartrate. The molecular formula is C26H37NO7 and the molecular weight is 475.58 g/mol. Tolterodine is the pharmacologically active compound; the tartrate salt form is used to improve the drug's stability and pharmaceutical properties.
Excipients
The extended-release formulation uses a proprietary multi-particulate bead technology. The capsule contains many small beads, each coated with a release-controlling polymer that governs the rate of drug dissolution. The key excipients include:
- Capsule contents: Sucrose stearate, maize starch (corn starch), hypromellose (hydroxypropyl methylcellulose), microcrystalline cellulose, ethylcellulose, medium-chain triglycerides, oleic acid, and sodium lauryl sulfate
- Capsule shell: Gelatin, indigo carmine (E132), titanium dioxide (E171), iron oxide yellow (E172), and other colorants depending on the strength (the 2 mg capsule and 4 mg capsule have different color combinations for identification purposes)
- Printing ink: Shellac, propylene glycol, and iron oxide black
The 2 mg capsule is typically identified by a specific color combination (green/green or blue/blue, depending on the manufacturer and market) and is printed with dosage information. The 4 mg capsule has a different color combination (blue/blue or dark blue/dark blue) for easy identification. Always check the packaging and capsule markings to confirm the correct strength before administration.
Patients with known intolerances should be aware that the formulation contains sucrose. Patients with rare hereditary problems of fructose intolerance, glucose-galactose malabsorption, or sucrase-isomaltase insufficiency should consult their doctor before taking this medicine. The product does not contain lactose, gluten, or tartrazine.
Frequently Asked Questions About Detrusitol SR
Detrusitol (immediate-release) contains tolterodine tartrate in an immediate-release tablet taken twice daily (typically 2 mg twice daily). Detrusitol SR (sustained/extended-release) contains the same active ingredient in a specially formulated capsule taken once daily (typically 4 mg once daily). The SR formulation releases tolterodine gradually over 24 hours, producing smoother plasma levels with lower peak concentrations. This results in fewer anticholinergic side effects, particularly dry mouth (approximately 23% with SR vs. 30% with immediate-release), while providing equivalent or superior symptom control. Most prescribers now prefer the extended-release formulation due to its improved tolerability and more convenient once-daily dosing.
No, the Detrusitol SR capsule must be swallowed whole with water. You should not crush, chew, or open the capsule. The extended-release mechanism depends on the intact bead coating to control drug release over 24 hours. Crushing or opening the capsule would destroy this mechanism, causing the entire dose to be released at once. This rapid-release scenario could increase the risk of side effects (particularly severe dry mouth and other anticholinergic symptoms) while also reducing the duration of therapeutic effect. If you have difficulty swallowing capsules, speak with your doctor about alternative formulations or treatments.
Some patients may notice a reduction in urgency and frequency symptoms within the first one to two weeks of starting Detrusitol SR. However, the full therapeutic benefit typically develops over 4 to 8 weeks of consistent daily use, as the bladder gradually adapts to the reduced stimulation. Your doctor will usually evaluate the effectiveness of treatment after 2 to 3 months. It is important to continue taking the medication as prescribed even if you do not notice immediate improvement. If there is no meaningful improvement after 8 to 12 weeks of treatment at the appropriate dose, your doctor may consider alternative therapies.
Detrusitol SR can be used in elderly patients, but extra caution is warranted. Elderly patients are more susceptible to anticholinergic side effects, including dry mouth, constipation, blurred vision, and importantly, cognitive impairment (confusion, memory problems). Long-term anticholinergic use in the elderly has been associated with an increased risk of cognitive decline and dementia in observational studies. It is recommended to start with the lower dose (2 mg once daily) in frail elderly patients and to reassess the need for treatment regularly. Non-pharmacological approaches (bladder training, pelvic floor exercises) should be maximized. In elderly patients already taking cholinesterase inhibitors for dementia, non-anticholinergic alternatives such as mirabegron should be considered.
There is no specific contraindication to moderate alcohol consumption while taking Detrusitol SR. However, alcohol can worsen some side effects of Detrusitol SR, including dizziness, drowsiness, and impaired concentration. Additionally, alcohol is a bladder irritant and diuretic, which means it can increase urinary frequency and urgency, potentially counteracting the beneficial effects of the medication. Caffeine has similar bladder-irritant properties. For optimal management of overactive bladder, it is advisable to limit both alcohol and caffeine intake. If you choose to drink alcohol, do so in moderation and be aware of the potential for increased sedation.
If Detrusitol SR does not provide adequate symptom relief or causes unacceptable side effects, several alternatives are available. Other antimuscarinic medications include solifenacin (Vesicare), darifenacin (Enablex), fesoterodine (Toviaz), and oxybutynin (Ditropan). Mirabegron (Betmiga/Myrbetriq), a beta-3 adrenergic agonist, works through a completely different mechanism and does not have anticholinergic side effects, making it a good option for patients who are intolerant of antimuscarinics or who take cholinesterase inhibitors. For patients who fail pharmacological therapy, third-line options include onabotulinumtoxinA (Botox) injections into the bladder wall, sacral neuromodulation (InterStim), and percutaneous tibial nerve stimulation (PTNS). Your healthcare provider can help determine the most appropriate next step based on your specific situation.
References
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- U.S. Food and Drug Administration (FDA). Detrol LA (tolterodine tartrate extended-release capsules) – Prescribing Information. Last revised 2024. Available at: www.accessdata.fda.gov
- European Association of Urology (EAU). Guidelines on Management of Non-Neurogenic Female Lower Urinary Tract Symptoms. 2024 Edition. Available at: uroweb.org/guidelines
- American Urological Association (AUA)/Society of Urodynamics, Female Pelvic Medicine & Urogenital Reconstruction (SUFU). Diagnosis and Treatment of Overactive Bladder (Non-Neurogenic) in Adults: AUA/SUFU Guideline Amendment 2023. J Urol. 2023;210(5):746–753.
- International Continence Society (ICS). Standardisation of Terminology in Lower Urinary Tract Function. Neurourol Urodyn. 2002;21(2):167–178.
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