Tolterodine: Competitive Muscarinic Receptor Antagonist for Overactive Bladder

Tolterodine (brand names Detrusitol, Detrol, and generic preparations) is a competitive muscarinic receptor antagonist that has been used since 1998 for the treatment of overactive bladder (OAB). It was one of the first medications specifically developed for this indication and paved the way for the diverse range of active substances available today, including Solifenacin, Darifenacin, Fesoterodin, and others.

An overactive bladder affects approximately 12 to 17 percent of adults in Western countries, with increasing frequency after age 60. Symptoms include urgency, urinary frequency, and in some patients, urge incontinence. Quality of life can be significantly impaired, and many affected individuals delay discussing this with their physician. Tolterodine is an established first line option for pharmacological therapy after behavioral measures and pelvic floor training.

Mechanism of Action

The detrusor muscle of the urinary bladder is innervated parasympathetically via the vagus and pelvic plexus. Acetylcholine binds to muscarinic M2 and M3 receptors on smooth muscle and triggers contraction. While M2 receptors are numerically most abundant in the bladder, M3 receptors primarily mediate the contractile function.

Tolterodine competitively blocks both receptor subtypes without pronounced selectivity. This reduces spontaneous bladder contraction, the detrusor relaxes, bladder volume increases, and urgent urination decreases. The lack of selectivity for the bladder compared to other tissues (salivary glands, gastrointestinal tract, eye) explains the typical anticholinergic side effects.

Tolterodine is metabolized in the liver via CYP2D6 to the active metabolite 5-hydroxymethyltolterodine, which is similarly effective (Fesoterodin is a prodrug that directly converts to 5-HMT). In approximately 7 percent of the population with CYP2D6 poor metabolizer genotype, tolterodine is predominantly degraded via CYP3A4, resulting in higher plasma levels and stronger side effects.

Indications

• Overactive bladder (OAB): Symptoms of urgency, urinary frequency, urge incontinence
• Detrusor instability after stroke, multiple sclerosis, Parkinson disease: Neurogenic bladder overactivity
• Postoperative bladder spasms: After urological procedures (off label)
• Pediatric age: Tolterodine approved in children from age 5 years for neurogenic detrusor hyperactivity (spina bifida), Pediatric Investigation Plan available

Dosage and Administration

Adults: 2 mg twice daily (standard form) or 4 mg once daily sustained release. For renal or hepatic insufficiency: Reduce dose to 1 mg twice daily or 2 mg sustained release.

With CYP3A4 inhibitor comedication (Ketoconazol, Itraconazol, Erythromycin): Reduce dose to 1 mg twice daily. Therapeutic success: First improvement usually within 2 weeks, full effect after 8 to 12 weeks. If response is inadequate, consider switching to a more selective agent or combination therapy with Mirabegron.

Side Effects

Common (anticholinergic): Dry mouth (most common side effect, approximately 30 percent), constipation, visual disturbances (accommodation disorder), fatigue, dizziness, headache, dry skin.

Occasional: Tachycardia, urinary retention (particularly in men with benign prostatic hyperplasia), oral mucosa ulceration, confusion especially in elderly patients, increased fall risk.

Rare: Acute angle closure glaucoma, QT prolongation on ECG, allergic reactions, anaphylactoid reactions.

Important, Anticholinergic burden: Tolterodine contributes to the so called anticholinergic burden, which is associated with cognitive decline, dementia, and fall risk. Particularly in elderly patients and with polypharmacy, the indication should be reviewed regularly and critically.

Drug Interactions

• Other anticholinergic agents (Tricyclic antidepressants, Diphenhydramine, Atropine): Additive anticholinergic burden, increased dry mouth, constipation, cognitive symptoms
• Cholinesterase inhibitors (Donepezil, Galantamine, Rivastigmine): Mutual antagonism of effects, combination should be critically reconsidered
• Strong CYP3A4 inhibitors (Ketoconazol, Itraconazol, Clarithromycin, HIV protease inhibitors): Increased tolterodine levels, dose reduction required
• QT prolonging agents (Sotalol, Amiodarone, Erythromycin): Additive QT prolongation, caution advised
• Alcohol: Enhances fatigue and cognitive effects

Special Precautions

Pregnancy and nursing: Data limited, use only after careful consideration of indication. If needed during pregnancy, behavioral measures and pelvic floor training are preferred.

Angle closure glaucoma: Tolterodine can increase intraocular pressure and is contraindicated in untreated angle closure glaucoma. Before starting therapy, patients should be informed of warning symptoms (acute eye pain, red eye, vision loss, headache, nausea).

Urinary retention: Patients with residual urine or bladder emptying disorders should undergo urological evaluation before therapy, with postvoid residual measurement and prostate assessment in men.

Driving ability: Tolterodine can cause fatigue, blurred vision, and concentration difficulties, which may impair driving ability.

You May Also Be Interested In

• Solifenacin, M3 selective antagonist
• Solifenacin succinate, common salt form
• Fesoterodin, prodrug to 5-HMT
• Mirabegron, Beta 3 adrenoreceptor agonist with different mechanism
• Oxybutynin, older anticholinergic

Frequently Asked Questions

Sources

• EMA Product Information Tolterodine Preparations
• DGU S2k Guideline Overactive Bladder
• Gelbe Liste, Tolterodine Active Substance Profile
• BfArM, Federal Institute for Drugs and Medical Devices