Trospium chloride is a synthetic quaternary ammonium compound belonging to the antimuscarinic (anticholinergic) class of drugs. It is primarily used for the treatment of overactive bladder (OAB), a condition characterized by urinary urgency, increased urinary frequency and urge urinary incontinence. It works by competitively blocking acetylcholine at muscarinic receptors in the urinary bladder, thereby reducing involuntary contractions of the detrusor muscle and relaxing bladder smooth muscle. This action increases bladder storage capacity and improves control over urination. Trospium chloride is commonly available as immediate-release tablets and extended-release capsules for oral administration. It was approved by the US FDA for overactive bladder treatment in 2004. More recently, on September 26, 2024, the FDA approved COBENFY, a combination of xanomeline and trospium chloride, for the treatment of schizophrenia in adults. Trospium chloride helps improve bladder function and reduce urinary symptoms, thereby enhancing patients' quality of life.
BRAND NAMES
Sanctura – Brand name available as immediate-release tablets for the treatment of overactive bladder.
Sanctura XR – Extended-release formulation used to manage urinary urgency, frequency and urge urinary incontinence.
MECHANISM OF ACTION
Trospium chloride is an antimuscarinic agent that competitively blocks muscarinic acetylcholine receptors, particularly M2 and M3 receptors, in the urinary bladder. This inhibits the action of acetylcholine on the detrusor muscle, reducing involuntary bladder contractions and relaxing the bladder. As a result, it increases bladder capacity and decreases urinary urgency, frequency and urge urinary incontinence.
PHARMACOKINETICS
Absorption
Trospium chloride is absorbed through the gastrointestinal tract following oral administration. It exhibits relatively poor absorption and has an oral bioavailability of approximately 9.6%. The drug reaches its peak plasma concentration within approximately 5–6 hours after administration of the immediate-release formulation. Its absorption is significantly affected by food, particularly high-fat meals, which can reduce the amount of drug absorbed into the bloodstream.
Distribution
Trospium chloride is widely distributed throughout the body after absorption into the bloodstream. It shows low plasma protein binding of approximately 50–85%. Due to its quaternary ammonium structure, it is highly polar and has limited ability to cross the blood–brain barrier. Therefore, its entry into the central nervous system is minimal, reducing the likelihood of central nervous system side effects. The drug is distributed mainly in extracellular fluids and reaches its site of action in the urinary bladder, where it blocks muscarinic receptors and helps relax the detrusor muscle.
Metabolism
Trospium chloride undergoes limited metabolism in the liver after oral administration. A significant portion of the drug remains unchanged in the body and is not extensively metabolized by hepatic enzymes. Its metabolism mainly occurs through hydrolysis and conjugation processes, including ester hydrolysis and glucuronidation. The drug has minimal involvement with the cytochrome P450 enzyme system, which reduces the possibility of certain metabolic drug interactions. Most of the administered drug is eliminated unchanged through the kidneys, while only a small portion is metabolized before excretion.
Elimination
Trospium chloride is eliminated mainly through the kidneys via urine, with a large proportion of the administered dose excreted as unchanged drug. A small amount is eliminated through feces after metabolism. The drug has an elimination half-life of approximately 20 hours, although it may vary depending on kidney function and the formulation used. Renal clearance plays an important role in its removal from the body. In patients with impaired kidney function, drug accumulation may occur, so dose adjustment and careful monitoring are necessary.
PHARMACODYNAMICS
Trospium chloride is an antimuscarinic (anticholinergic) drug that acts by competitively blocking acetylcholine at muscarinic receptors, particularly in the urinary bladder. It reduces the stimulation of the detrusor muscle, resulting in relaxation of bladder smooth muscle and decreased involuntary contractions. This action increases the bladder's storage capacity and helps control urination. It effectively reduces symptoms of overactive bladder, such as urinary urgency, increased urinary frequency and urge urinary incontinence.
ADMINISTRATION
The extended-release capsule is generally taken once daily in the morning before food. It should be taken regularly as prescribed by the physician to achieve the desired therapeutic effect.
DOSAGE AND STRENGTH
The usual recommended adult dosage for immediate-release tablets is 20 mg twice daily, preferably on an empty stomach with water, at least one hour before meals. The dosage may be adjusted according to the patient's age, kidney function, medical condition and response to treatment. In patients with severe renal impairment, dose adjustment is required to prevent drug accumulation and adverse effects.
DRUG INTERACTIONS
Trospium chloride may interact with several medications, particularly drugs that have anticholinergic effects. When taken with other anticholinergic medicines, such as antihistamines, tricyclic antidepressants and antipsychotics, it may increase side effects like dry mouth, constipation, blurred vision and urinary retention. It may also reduce the effects of medicines that increase gastrointestinal movement, such as metoclopramide. Therefore, caution should be taken when using trospium chloride with other medications, and medical advice is recommended to avoid unwanted drug interactions.
FOOD INTERACTIONS
Trospium chloride absorption is influenced by food intake. Taking the medicine with food may decrease the amount of drug absorbed into the bloodstream, reducing its effectiveness. Therefore, it is recommended to administer the medication on an empty stomach with water, at least one hour before meals. Patients should follow the prescribed dosing instructions and maintain a consistent administration schedule for better therapeutic results.
CONTRAINDICATIONS
It is also contraindicated in patients with certain gastrointestinal obstructive conditions. Special care is needed in individuals with impaired kidney function, intestinal disorders and difficulty emptying the bladder, as the drug may worsen these conditions. Proper medical evaluation is necessary before starting treatment to ensure safe and effective use.
SIDE EFFECTS
Dry mouth
Constipation
Headache
Dizziness
Blurred vision
Nausea
Abdominal pain
Dry eyes
Over Dose
Overdose of trospium chloride may cause excessive anticholinergic effects due to increased blocking of muscarinic receptors. Symptoms may include severe dry mouth, blurred vision, constipation, rapid heartbeat, difficulty in urination, urinary retention, dizziness and confusion. In severe cases, it may cause reduced sweating, increased body temperature and other signs of anticholinergic toxicity. Immediate medical attention is required. Treatment mainly involves supportive care, monitoring of vital signs and management of symptoms under medical supervision.
TOXICITY
Trospium chloride toxicity occurs mainly due to excessive anticholinergic activity in the body. It may produce symptoms such as severe dry mouth, blurred vision, constipation, urinary retention, rapid heartbeat, dizziness and confusion. In severe cases, it can cause reduced sweating, increased body temperature and altered mental status. Toxicity is managed by discontinuing further doses pending medical assessment, providing supportive treatment, monitoring vital signs and treating anticholinergic symptoms under medical supervision.
