Mirabegron or Solifenacin: Four BEYOND Checks

A bladder medicine that leaves you planning every outing around toilets deserves a review. AUA/SUFU¹ allows switching within or between medicine classes after inadequate benefit or intolerable side effects. The choice should include the side effects you can tolerate, other medicines and the symptoms you want to improve.¹

Selected switchers

BEYOND randomized 1,887 adults dissatisfied with antimuscarinic effectiveness to mirabegron 50 mg or solifenacin 5 mg daily for 12 weeks. It excluded primarily intolerant patients and those whose last medicine was solifenacin. Astellas funded, designed and analyzed it; authors included employees.²

Unmet target

Noninferiority meant ruling out more than 0.20 extra daily urinations with mirabegron. Adjusted reductions were 2.95 versus 3.13; the solifenacin-minus-mirabegron difference was −0.18 (95% CI −0.42 to 0.06). That failed the margin without proving solifenacin superior.²

Analysis limits

The primary analysis excluded noncompleters and major protocol violations; registry results used last observations carried forward.²³

No placebo arm separated treatment effects from other improvements.²

Different precautions

Dry mouth: 29/936 (3.1%) versus 54/934 (5.8%), respectively, without formal testing of adverse-event rates.²

Mirabegron can raise blood pressure; its US label recommends periodic checks and advises against use with severe uncontrolled hypertension: systolic ≥180 or diastolic ≥110 mm Hg. It also warns about urinary retention with bladder-outlet obstruction or concurrent antimuscarinics. Its CYP2D6 inhibition can increase concentrations of other medicines, requiring monitoring or adjustment.⁴

Solifenacin is contraindicated with urinary retention, gastric retention or uncontrolled narrow-angle glaucoma. Confusion, hallucinations and sleepiness are reported central nervous system effects. The label advises against use in people at high risk of QT prolongation, including those taking medicines that prolong QT. Kidney and liver function and strong CYP3A4 inhibitors can restrict dosing.⁵

AUA/SUFU¹ recommends reassessment within four to eight weeks of starting medicine and discussing potential dementia and cognitive risks with antimuscarinics. Associations with dementia do not establish causation; the short BEYOND trial cannot answer that long-term question.¹

Bring a three-day bladder diary and a medicine list to review. Ask which symptom will determine benefit, when to reassess and which side effects should prompt contact. “The Next Rungs” in Laugh, Sneeze, Jump discusses prescription options and total anticholinergic load; it can help prepare that conversation.¹