Fesoterodine (Dosage)

Fesoterodine is an antimuscarinic drug used to treat overactive bladder syndrome. The presence of polymorphisms in the CYP2D6 gene influences the pharmacokinetics of the drug so knowing the "metabolic status" of the individual can help to achieve a better dose adjustment.

Fesoterodine is used to treat overactive bladder (a condition in which the muscles of the bladder contract uncontrollably, causing frequent urination, an urgent need to urinate, and an inability to control urination). Fesoterodine is in a class of medications called antimuscarinics. It works by relaxing the bladder muscles to prevent urgent, frequent, or uncontrollable urination.


Fesoterodine is a specific competitive antagonist of muscarinic receptors. It is rapidly and extensively hydrolyzed by plasma esterases giving rise to the 5-hydroxymethyl derivative, which is the major active metabolite and the main responsible for the pharmacological action.


Fesoterodine hypersensitivity, urinary retention, gastric retention, uncontrolled angle-closure glaucoma, myasthenia gravis, severe liver failure, severe ulcerative colitis, toxic megacolon.

Do not prescribe fesoteridone or closely monitor its use if used concomitantly with strong CYP3A4 inhibitors in patients with renal or hepatic impairment.


Cautions should be taken when the patient presents significant obstruction of the bladder outlet tract, with risk of urinary retention; gastrointestinal obstructive disorders (pyloric stenosis); gastroesophageal reflux and/or those who take substances (oral bisphosphonates) at the same time that can cause or worsen esophagitis; decreased gastrointestinal motility; autonomic neuropathy; controlled angle closure glaucoma; patients at risk of cardiac QT prolongation (hypokalaemia, bradycardia and concomitant administration of drugs that prolong the QT interval), pre-existing relevant heart diseases (myocardial ischemia, arrhythmia, CHF); detrusor hyperactivity of neurogenic origin.

Caution should be exercised when prescribing or adjusting doses in patients with impaired hepatic or renal function that are taking fesoterodine concomitantly with strong or moderate inhibitors of cytochrome CYP3A4 or strong inhibitors of CYP2D6. Concomitant use with a strong CYP3A4 inducer (carbamazepine, rifampicin, phenobarbital, phenytoin, St. John's wort) is not recommended.

Fesoterodine is not recommended for children and adolescents under 18 years old.

There is a risk of angioedema, if it appears stop treatment with fesoterodine and immediately administer an appropriate treatment.

Its use is not recommended during pregnancy and lactation because there are no toxicity data.


Fesoterodine reduces the effect of metoclopramide.

Caution when fesoterodine is co-administered with other antimuscarinics and substances that have anticholinergic properties (eg amantadine, tricyclics antidepressants, certain neuroleptics), as this can lead to increased therapeutic effect and adverse reactions.

The plasma concentration of fesoterodine is increased by: strong CYP3A4 inhibitors (for example, atazanavir, clarithromycin, indinavir, itraconazole, ketoconazole, nefazodone, nelfinavir, ritonavir (including any ritonavir-boosted protease inhibitor treatment), saquanivir, and telithromycin).

The plasma concentration of fesoteridone is decreased by: treatment with inducers of CYP3A4 (eg, carbamazepine, rifampicin, phenobarbital, phenytoin, St. John's wort). Concomitant use is not recommended.

Concomitant administration with a strong CYP2D6 inhibitor may result in increased fesoterodine exposure and adverse reactions. Dose reduction to 4 mg may be necessary if given with strong CYP2D6 inhibitors.


Dizziness, headache, dry eye, dry throat; dry mouth, abdominal pain, diarrhea, dyspepsia, constipation, nausea; dysuria; insomnia, hoarseness, back pain.

There are other more serious but less common side effects, such as: swelling of the face, throat, tongue or lips and difficulty swallowing or breathing. If you have any of these symptoms, stop taking fesoterodine and go to the emergency services.


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