Are two drugs more beneficial than one for treating patients with overactive bladder?

This article reviewed several studies that compared the effectiveness of two drugs compared to one drug for treating symptoms of overactive bladder (OAB). The authors concluded that the combination of mirabegron (Myrbetriq) and solifenacin (Vesicare) was more effective than each drug alone and had similar side effects in these patients.

OAB is characterized by an urgency to urinate, frequent trips to the bathroom, waking at night to urinate and urine leakage. This can affect a patient’s quality of life. It is caused by the muscles of the bladder abnormally contracting when the bladder is empty or has just a small amount of urine. 

There are two types of drugs often used to treat OAB. The first type is called antimuscarinics. They work by blocking the signals from the brain that tell the bladder muscles to contract. The second type is called β3-adrenoreceptor agonist and work by making the bladder muscles relax. Solifenacin is a type of β3-adrenoreceptor agonist. Mirabegron is a type of antimuscarinic drug. Sometimes two drugs are recommended for patients where one drug is not effective. However, it is not clear if two drugs are superior to one drug. 

This study examined several clinical trials that compared solifenacin and mirabegron to the individual drugs alone to treat patients with OAB.

The combination of solifenacin and mirabegron improved several symptoms of OAB compared to each drug alone across several studies. One study showed that incontinence (involuntary urine leakage) was reduced by 1.98 times per day for patients taking 50 mg of mirabegron and 5 mg of solifenacin after 12 weeks. This was compared to 1.76 times for patients taking mirabegron alone and 1.79 for patients taking solifenacin alone.

The number of bladder muscle contractions was reduced by the combination of solifenacin and mirabegron also. One study showed that the number of contractions per day was reduced by 2.6 for patients taking solifenacin and mirabegron after 12 months. The number of contractions per day was reduced by 2.1 for patients taking mirabegron alone and by 2.2 for patients taking solifenacin alone.

The volume of urine excreted was increased by the combination of solifenacin and mirabegron. One study recorded an increase of 28.05 ml in the volume of urine after taking solifenacin and mirabegron for 12 weeks. This was compared to an increase of 16.52 ml after taking solifenacin alone.

Patients’ quality of life was improved more so by the combination of solifenacin and mirabegron.   Patients reported a 3.15 times higher quality of life score after taking solifenacin and mirabegron compared to solifenacin alone.

There were no significant differences in side effects experienced by patients. Approximately 47% of patients reported one or more side effects after taking solifenacin and mirabegron together or alone.  

The study concluded that solifenacin and mirabegron together are more effective for treating patients with OAB than each drug alone. Also, the authors concluded that the combination of drugs did not increase the number of side effects.

The manufacturer of solifenacin and mirabegron, Astellas Pharma, funded this study. The studies reviewed in this article had different follow-up periods and study designs.