Initial management of overactive bladder includes behavioural modifications, urge inhibition and pharmacotherapy. until recently, antimuscarinics have been cornerstone pharmacotherapeutic agents. their long term usage has been limited due to side effects particularly, but not limited to, constipation, dry mouth, cognitive impairment and tachycardia. Mirabegron, a beta3 agonist, is new kid on the block been available in India since mid 2018. The potential benefits over antimuscarics are significantly less side effects and equivalent efficacy. the potential side effect of hypertension has not been found significant over placebo. Already found a place as second line therapy and comination therapy, it is increasingly being accepted as first line alternative.

1. MIRABEGRON: NEW KID ON
THE BLOCK
​Dr Mayank Mohan Agarwal
MBBS, MS, MRCS(Ed), ​DNB, M.Ch (PGIMER, Chandigarh)
VMMF and IAUA Fellowships Uro-Oncology, Pelvic Floor Reconstruction
(MSKCC, NY; UCLA, LA; WFUBMC, NC)​
Ex-Associate Professor of Urology (PGIMER, Chandigarh)
Consultant and Head of Urology
(Aster) Dr. Ramesh Cardiac and Multispecialty Hospitals Pvt. Ltd.
Guntur (AP), India

2. INTRODUCTION
• Physiology of lower urinary tract
• Receptors in lower urinary tract
• Pathophysiology of overactive bladder
• Shortcomings of current medications
• Mirabegron – efficacy
• Mirabegron – safety
• Guideline statement

3. FILLING PHASE
+ SY
+ SO
- PSY
- SY
+ -
BLADDER ↔ URETHRA REFLEXES

4. VOIDING PHASE
- SY
- SO
+ PSY
- +
BLADDER ↔ URETHRA REFLEXES

6. OAB: definition
• urinary urgency, with or without urgency incontinence, usually with
increased daytime frequency and nocturia, if there is no proven
infection or other obvious pathology

7. OAB: pathogenesis

8. Patchy denervation is a common observation in DO, regardless of etiology (German et al, 1995;
Charlton et al, 1999; Drake et al, 2000; Mills et al, 2000). A smooth muscle cell deprived of its
innervation shows an upregulation of surface membrane receptors and may have altered membrane
potential, which increases the likelihood of spontaneous contraction in that cell.

9. Antimuscarinics

11. Adverse effects

12. Adverse effects
• QT prolongation
- Not related to blockade of muscarinic receptors
- linked to inhibition of the hERG potassium channel in the heart
• CNS side effects
- cognitive dysfunction
- memory impairment
- Dizziness
- Fatigue
- headache

13. Mirabegron
• Beta 3 receptor agonist
• Mild alpha 1a and 1d blocker
• Mild M2 antagonist
Alexandre et al. Mirabegron relaxes urethral smooth muscle by a dual mechanism involving β3- adrenoceptor activation and α1-adrenoceptor
blockade. British Journal of Pharmacology (2016) 173 415–428 415

14. Efficacy of Mirabegron: vs placebo
• Meta-analysis (1)
• 4 phase III RCT’s
• SCORPIO
• ARIES
• CAPRICORN
• 178-CL-048
• N (Mirabegron) = 1759 N (placebo) = 1765
• Duration 50w (~1yr)
Cui et al. The efficacy and safety of mirabegron in treating OAB: a systematic review and meta-analysis of phase III trials. Int Urol Nephrol (2014) 46:275–284

15. Efficacy of Mirabegron: vs placebo
• Meta-analysis (1)
• 4 phase III RCT’s
• SCORPIO
• ARIES
• CAPRICORN
• 178-CL-048
• N (Mirabegron) = 1759 N (placebo) = 1765
Cui et al. The efficacy and safety of mirabegron in treating OAB: a systematic review and meta-analysis of phase III trials. Int Urol Nephrol (2014) 46:275–284
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
D incontinence
episodes
D no. of voids D no. of urgency
episodes
D. no. of nocturia
efficacy

16. Efficacy of Mirabegron: vs placebo
• Meta-analysis (1)
• 4 phase III RCT’s
• SCORPIO
• ARIES
• CAPRICORN
• 178-CL-048
• N (Mirabegron) = 1759 N (placebo) = 1765
• Duration 50w (~1yr)
Cui et al. The efficacy and safety of mirabegron in treating OAB: a systematic review and meta-analysis of phase III trials. Int Urol Nephrol (2014) 46:275–284
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
Adverse effects
p = NS

17. Efficacy of Mirabegron: vs placebo
• Meta-analysis (2)
• 5 phase III RCT’s
• N (placebo) = 1610
• N (Mirabegron 25) = 597
• N (Mirabegron 50) = 2354
• N (Mirabegron 100) = 1982
Wu et al. The Role of Mirabegron in Overactive Bladder: A Systematic Review and Meta-Analysis. Urol Int 2014;93:326–337

18. Efficacy of Mirabegron: vs placebo
• Meta-analysis (2)
• 5 phase III RCT’s
• N (placebo) = 1610
• N (Mirabegron 25) = 597
• N (Mirabegron 50) = 2354
• N (Mirabegron 100) = 1982
Wu et al. The Role of Mirabegron in Overactive Bladder: A Systematic Review and Meta-Analysis. Urol Int 2014;93:326–337
INCONTINENCE EPISODES IN 24H

19. Efficacy of Mirabegron: vs placebo
• Meta-analysis (2)
• 5 phase III RCT’s
• N (placebo) = 1610
• N (Mirabegron 25) = 597
• N (Mirabegron 50) = 2354
• N (Mirabegron 100) = 1982
Wu et al. The Role of Mirabegron in Overactive Bladder: A Systematic Review and Meta-Analysis. Urol Int 2014;93:326–337
NO. OF MICTURITIONS IN 24H

20. Efficacy of Mirabegron: vs placebo
• Meta-analysis (2)
• 5 phase III RCT’s
• N (placebo) = 1610
• N (Mirabegron 25) = 597
• N (Mirabegron 50) = 2354
• N (Mirabegron 100) = 1982
Wu et al. The Role of Mirabegron in Overactive Bladder: A Systematic Review and Meta-Analysis. Urol Int 2014;93:326–337
ADVERSE EFFECTS

21. Efficacy of Mirabegron: vs tolterodine
• Meta-analysis (2)
• 4 phase III RCT’s
• N (placebo) = 724
• N (Mirabegron 25) = 167
• N (Mirabegron 50) = 1472
• N (Mirabegron 100) = 1549
• N (tolterodine 4) = 1455
Wu et al. The Role of Mirabegron in Overactive Bladder: A Systematic Review and Meta-Analysis. Urol Int 2014;93:326–337

22. Efficacy of Mirabegron: vs tolterodine
• Meta-analysis (2)
• 4 phase III RCT’s
• N (placebo) = 724
• N (Mirabegron 25) = 167
• N (Mirabegron 50) = 1472
• N (Mirabegron 100) = 1549
• N (tolterodine 4) = 1455
Wu et al. The Role of Mirabegron in Overactive Bladder: A Systematic Review and Meta-Analysis. Urol Int 2014;93:326–337INCONTINENCE EPISODES IN 24H

23. Efficacy of Mirabegron: vs tolterodine
• Meta-analysis (2)
• 4 phase III RCT’s
• N (placebo) = 724
• N (Mirabegron 25) = 167
• N (Mirabegron 50) = 1472
• N (Mirabegron 100) = 1549
• N (tolterodine 4) = 1455
Wu et al. The Role of Mirabegron in Overactive Bladder: A Systematic Review and Meta-Analysis. Urol Int 2014;93:326–337
NO. OF MICTURITIONS IN 24H

24. Efficacy of Mirabegron: vs tolterodine
• Meta-analysis (2)
• 4 phase III RCT’s
• N (placebo) = 724
• N (Mirabegron 25) = 167
• N (Mirabegron 50) = 1472
• N (Mirabegron 100) = 1549
• N (tolterodine 4) = 1455
Wu et al. The Role of Mirabegron in Overactive Bladder: A Systematic Review and Meta-Analysis. Urol Int 2014;93:326–337ADVERSE EFFECTS

25. Adverse effects antimuscarinics
AUA 2014

26. Mirabegron add on to Solifenacin
• N = 223
Yamaguchi et al. Safety and efficacy of mirabegron as ‘add-on’ therapy in patients with overactive bladder treated with solifenacin: a post-marketing, open-label
study in Japan (MILAI study). BJU Int 2015; 116: 612–622

27. Mirabegron add on to Solifenacin
• N = 223
Yamaguchi et al. Safety and efficacy of mirabegron as ‘add-on’ therapy in patients with overactive bladder treated with solifenacin: a post-marketing, open-label
study in Japan (MILAI study). BJU Int 2015; 116: 612–622

28. Mirabegron add on to Solifenacin
• N = 223
Yamaguchi et al. Safety and efficacy of mirabegron as ‘add-on’ therapy in patients with overactive bladder treated with solifenacin: a post-marketing, open-label
study in Japan (MILAI study). BJU Int 2015; 116: 612–622

29. Mirabegron add on to Solifenacin
• N = 223
Yamaguchi et al. Safety and efficacy of mirabegron as ‘add-on’ therapy in patients with overactive bladder treated with solifenacin: a post-marketing, open-label
study in Japan (MILAI study). BJU Int 2015; 116: 612–622

30. Mirabegron add on to Solifenacin
• N = 2174
• Combination = 727
• Solifenacin 5 = 728
• Solifenacin 10 =719
Drake et al. Efficacy and Safety of Mirabegron Add-on Therapy to Solifenacin in Incontinent Overactive Bladder Patients with an Inadequate Response to Initial 4-Week
Solifenacin Monotherapy: A Randomised Double-blind Multicentre Phase 3B Study (BESIDE). EUROPEAN UROLOGY 7 0 ( 2 0 1 6 ) 1 3 6 – 1 4 5

31. Mirabegron add on to Solifenacin

32. Mirabegron add on to Solifenacin
• N = 2174
• Combination = 727
• Solifenacin 5 = 728
• Solifenacin 10 =719
Drake et al. Efficacy and Safety of Mirabegron Add-on Therapy to Solifenacin in Incontinent Overactive Bladder Patients with an Inadequate Response to Initial 4-Week
Solifenacin Monotherapy: A Randomised Double-blind Multicentre Phase 3B Study (BESIDE). EUROPEAN UROLOGY 7 0 ( 2 0 1 6 ) 1 3 6 – 1 4 5

33. Mirabegron add on to Solifenacin
• N = 2174
• Combination = 727
• Solifenacin 5 = 728
• Solifenacin 10 =719
Drake et al. Efficacy and Safety of Mirabegron Add-on Therapy to Solifenacin in Incontinent Overactive Bladder Patients with an Inadequate Response to Initial 4-Week
Solifenacin Monotherapy: A Randomised Double-blind Multicentre Phase 3B Study (BESIDE). EUROPEAN UROLOGY 7 0 ( 2 0 1 6 ) 1 3 6 – 1 4 5
INCONTINENCE EPISODES IN 24H

34. Mirabegron add on to Solifenacin
• N = 2174
• Combination = 727
• Solifenacin 5 = 728
• Solifenacin 10 =719
Drake et al. Efficacy and Safety of Mirabegron Add-on Therapy to Solifenacin in Incontinent Overactive Bladder Patients with an Inadequate Response to Initial 4-Week
Solifenacin Monotherapy: A Randomised Double-blind Multicentre Phase 3B Study (BESIDE). EUROPEAN UROLOGY 7 0 ( 2 0 1 6 ) 1 3 6 – 1 4 5
NO. OF MICTURITIONS IN 24H

35. Mirabegron add on to Solifenacin
• N = 2174
• Combination = 727
• Solifenacin 5 = 728
• Solifenacin 10 =719
Drake et al. Efficacy and Safety of Mirabegron Add-on Therapy to Solifenacin in Incontinent Overactive Bladder Patients with an Inadequate Response to Initial 4-Week
Solifenacin Monotherapy: A Randomised Double-blind Multicentre Phase 3B Study (BESIDE). EUROPEAN UROLOGY 7 0 ( 2 0 1 6 ) 1 3 6 – 1 4 5

37. Possibility of continuing medication
• N = 380 (mirabegron)
• N = 2248 (tolterodine)

38. Possibility of continuing medication
• N = 380 (mirabegron)
• N = 2248 (tolterodine)
0
10
20
30
40
50
60
70
80
30 d 90 d 180 d
Probability of remaining on treatment
mirabegron tolterodine

39. What do guidelines say
• EUROPEAN ASSOCIATON OF UROLOGY 2018

40. What do guidelines say
• AMERICAN UROLOGICAL ASSOCIATION 2014

41. PHARMACOLOGY
• ABSORPTION
- 25% 25MG
- 35% 50MG
• TMAX – 3-4 HOURS
• T1/2 – 40HOURS
• 71% PLASMA PROTEIN BOUND
• METABOLIZED IN LIVER WITH CYTP450 SYSTEM
REDUCED WITH FOOD
HIGHER IN WOMEN
55% IN URINE
34% IN FECES
UNCHANGED

42. CAUTIONS
• PREGNANCY CATEGORY C
• DOSE ADJUSTMENT IN
• SEVERE RENAL DISEASE (AUC ↑ 118% AND CMAX ↑ 92%)
• MODERATE LIVER DISEASE (AUC ↑ 65% AND CMAX ↑ 175%)
• Caution with CYP2D6/3A4 substrates with a narrow therapeutic index
• Anticoagulants
• Antidepressants
• antiepileptics

43. CONCLUSION
• Mirabegron is safe with side effect profile similar to placebo
• Mirabegron is as effective as antimuscarinics in OAB
• Mirabegron can be considered as first line therapy alternative to
antimuscarinics
• Mirabegron added on to solifenacin is more effective than increasing
dose

44. THANK YOU