By: Arya Firoozan, PharmD Candidate c/o 2023

             Overactive bladder (OAB) is a condition that causes a sudden and frequent urge to urinate. It is also associated with incontinence and nocturia. Nocturia refers to waking up at night due to the urge to urinate. OAB is diagnosed if there is no other current infection or pathological reason for increased urination. ¹ Patients diagnosed with OAB oftentimes complain that they have to urinate too frequently during the daytime. Males have a higher prevalence of OAB without incontinence (overactive bladder syndrome dry), while females have a higher prevalence of OAB with incontinence (overactive bladder syndrome wet). The prevalence of OAB in women gets significantly higher with age. OAB affects many patients in the United States and has a national cost of 66 billion dollars annually. ¹ In December 2020, the Food and Drug Administration (FDA) approved vibegron (Gemtesa ®) as a new treatment for the symptoms of OAB. This novel drug is manufactured by Urovant Sciences. ²

Initial treatment of OAB primarily involves lifestyle modification. Patient education regarding adjustment of fluid intake and dietary adjustments plays a major role in managing OAB. Bladder training and pelvic muscle training may also have some use to regain control over the bladder. ¹ Drug treatments are only initiated after these initial lifestyle modifications are tried.

Antimuscarinic/anticholinergic medications are the main drug class that are used for the treatment of OAB. These include medications such as oxybutynin and tolterodine. Medications with anticholinergic properties have side effects that can be potentially harmful to the elderly. These include an increased risk of falls, fractures, confusion, blurred vision, and sedation. In addition, a study performed in the UK showed an association between anticholinergic medications and an increased risk of dementia. ³ These potentially severe side effects should be kept in mind by physicians and pharmacists when dealing with OAB in elderly patients.

Vibegron works as a selective beta-3 adrenergic agonist. This class has been more recently used as an alternative to anticholinergics. One of the first members of this class, mirabegron (Myrbetriq®), has been used to treat OAB since 2013. One of the unique features that distinguishes vibegron from mirabegron is that vibegron is unlikely to be metabolized by the CYP3A4 or CYP2D6 enzymes, which makes for lower risk of drug interactions. ³ Mirabegron is a minor substrate and inhibitor of CYP2D6. Thus, if it is co-administered with another CYP2D6 substrate, mirabegron can increase the concentration of the other agent. ⁴

             The FDA approved vibegron based on evidence from one clinical trial conducted in April 2018. In this phase 3, randomized, double-blind, placebo and active (tolterodine) controlled multicenter trial, patients received once daily treatments with either vibegron, placebo or tolterodine. Patients receiving vibegron received a 75mg oral dose per day for twelve weeks and were asked to record the number of urgency episodes over the twelve weeks, along with the frequency of incontinence episodes. The participants also filled out questionnaires about their quality of life regarding OAB. ⁵ The patients that completed the trial reported a decrease of 1.8 micturition episodes per day vs. a 1.6 episode decrease for tolterodine. There was an average decrease of 2 incontinence episodes per day for vibegron vs. a 1.8 episode decrease for tolterodine. The adverse effects were all similar between the placebo, vibegron and tolterodine. ⁶ However, concomitant use of vibegron with digoxin raises some concerns. Vibegron can increase the maximum concentration levels of digoxin in the body, so serum digoxin levels should be monitored before initiating and during therapy with vibegron. There is no available data on vibegron use in pregnant women, however vibegron had no effects on development during animal studies. ⁷

Overactive bladder syndrome is a common issue that has a potentially large impact on a patient’s quality of life. Looking to the future, vibegron could be efficacious in improving OAB symptoms as either a first or second-line option. Current assessment and diagnosis of the disease usually lead to antimuscarinics or mirabegron being prescribed. Vibegron presents itself as an option that has fewer drug interactions, but more research comparing it to its beta-3 adrenergic agonist family members, namely mirabegron, must be completed for it to cement itself as a viable alternative.

Sources:

1. Wallace KM, Drake MJ. Overactive bladder. F1000Res. 2015. pii: F1000 Faculty Rev-1406
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5. ClinicalTrials.gov. A Study to Examine the Safety and Efficacy of a New Drug in Patients With Symptoms of Overactive Bladder (OAB) (Empowur). NIH U.S. National Library of Medicine. https://clinicaltrials.gov/ct2/show/NCT03492281. Published 04/10/2018. Last Updated 01/18/2020.
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Published by Rho Chi Post