Solifenacin is also not recommended for use in people with severe liver failure, clinically significant bladder outlet obstruction in the absence of clean intermittent catheterization, decreased gastrointestinal motility (slowed intestinal contractions), or at high risk of QT prolongation (an electrical disturbance where the heart muscle takes longer than normal to recharge between beats), including people with a known history of QT prolongation and people taking medications known to prolong the QT interval. Side effects
The most common side effects of solifenacin are dry mouth, constipation and urinary tract infection. As all anticholinergics, solifenacin may rarely cause hyperthermia due to decreased perspiration. Somnolence (sleepiness or drowsiness) has been reported. Severe allergic reactions, such as angioedema (swelling beneath the skin) and anaphylaxis, have been reported in people treated with solifenacin succinate and may be life-threatening. Interactions
Solifenacin is metabolized in the liver by the cytochrome P450 enzyme CYP3A4. When administered concomitantly with drugs that inhibit CYP3A4, such as ketoconazole, the metabolism of solifenacin is impaired, leading to an increase in its concentration in the body and a reduction in its excretion.As stated above, solifenacin may also prolong the QT interval. Therefore, administering it concomitantly with drugs which also have this effect, such as moxifloxacin or pimozide, can theoretically increase the risk of arrhythmia. Pharmacology
Mechanism of action
Solifenacin is a competitive cholinergic receptor antagonist, selective for the M3 receptor subtype. The binding of acetylcholine to these receptors, particularly M3, plays a critical role in the contraction of smooth muscle.
By preventing the binding of acetylcholine to these receptors, solifenacin reduces smooth muscle tone in the bladder, allowing the bladder to retain larger volumes of urine and reducing the number of micturition, urgency and incontinence episodes. Because of a long elimination half life, a once-a-day dose can offer 24-hour control of the urinary bladder smooth muscle tone. Pharmacokinetics
Peak plasma concentrations are reached three to eight hours after absorption from the gut. In the bloodstream, 98% of the substance are bound to plasma proteins, mainly acidic ones. Metabolism is mediated by the liver enzyme CYP3A4 and possibly others. There is one known active metabolite, 4R-hydroxysolifenacin, and three inactive ones, the N-glucuronide, the N-oxide and the 4R-hydroxy-N-oxide. The elimination half-life is 45 to 68 hours. 69% of the substance, both in its original form and as metabolites, are excreted renally and 23% via the feces. Chemistry
Like other anticholinergics, solifenacin is an ester of a carboxylic acid containing (at least) an aromatic ring with an alcohol containing a nitrogen atom. While in the prototype anticholinergic atropine the bicyclic ring is tropane, solifenacin replaces it with quinuclidine. The free base is a yellow oil, while the salt solifenacin succinate forms yellowish crystals. History
The compound was studied using animal models by the Yamanouchi Pharmaceutical Co., Ltd. of Tokyo, Japan.