Solifenacin succinate

Vesicare (Arrow Pharmaceuticals)
5 mg and 10 mg tablets
Approved indication: overactive bladder
Australian Medicines Handbook section 13.1.1

Patients with overactive bladders may have urgency and frequency. Some may develop urge incontinence. If these symptoms are troublesome and do not respond to non-drug treatment an anticholinergic drug may help (see 'Anticholinergic drugs for overactive bladder', Aust Prescr 2006;29:22-4).

Solifenacin is an anticholinergic drug with a high affinity for the M₃ muscarinic receptors in smooth muscle. It is well absorbed and can be taken once a day. Solifenacin is metabolised in the liver by cytochrome P450 3A4 so it may interact with other drugs which inhibit or induce this enzyme. Most of the metabolites are excreted in the urine. The half-life is 45-68 hours, but this is prolonged by renal or hepatic impairment.

In a randomised double-blind trial, once-daily solifenacin was compared with placebo in 907 patients with overactive bladder. After 12 weeks the mean number of daily micturitions had reduced, from a baseline rate of about 12 in 24 hours, by 2.4 with solifenacin 5 mg and by 2.8 with solifenacin 10 mg. This was a statistical advantage over the placebo group who had 1.6 fewer micturitions per day. The reduction in incontinence showed a similar pattern with 1.3 fewer episodes in the placebo group and 1.6 fewer episodes with solifenacin 5 mg or 10 mg.¹

A pooled analysis of trials in patients over 65 years old showed some statistical advantages over placebo, but the absolute differences were small. Solifenacin 5 mg reduced incontinence by a median of 1 episode per day compared with 0.7 episodes with placebo and 1.5 episodes with solifenacin 10 mg. Patients taking placebo had one less micturition per day while those taking solifenacin 5 mg had two less micturitions. The median change with solifenacin 10 mg was 2.3 fewer micturitions per day.²

Despite its affinity for the M₃ receptor, solifenacin is not free of anticholinergic adverse effects. In the placebo-controlled trial, 23% of the patients taking solifenacin 10 mg developed a dry mouth compared with 7.7% of the solifenacin 5 mg group and 2.3% of the placebo group. Constipation and blurred vision were also more likely with solifenacin.¹In the pooled analysis, dry mouth affected 29.7% of the elderly people taking solifenacin 10 mg, 13.5% of those taking solifenacin 5 mg and 4.5% of the placebo group. Constipation affected 17.2%, 8.9% and 4.3% respectively.²

Solifenacin can prolong the QTinterval on the ECG. An ECG should be considered before starting treatment if there is a risk of QT_c prolongation.

Tolterodine is another recently approved drug for overactive bladder. It has been compared with solifenacin in 1200 patients over 12 weeks. The results were not analysed by the dose of solifenacin (5 mg or 10 mg), but overall there was no difference in the frequency of micturition. Solifenacin reduced daily micturitions by 2.45 compared to a reduction of 2.24 with tolterodine. Incontinence episodes per 24 hours reduced by a mean of 1.6 with solifenacin and 1.1 with tolterodine. Adverse events were slightly more frequent with solifenacin.³

Solifenacin will reduce urgency and this may improve the patient's quality of life. However, the efficacy is modest and the patient may have to endure adverse effects to obtain the benefit.

manufacturer provided additional useful information

The Transparency Score ( ) is explained in New drugs: transparency', Vol 37 No 1, Aust Prescr 2014;37:27.