Mirabegron(YM178) is a selective β3-adrenoceptor agonist with EC50 of 22.4 nM.
IC50 Value: 22.4 nM(EC50)
Target:  β3-adrenoceptor
in vitro: Mirabegron concentration-dependently relaxes rat and Human bladder smooth muscle strips precontracted with 10-6 M or 10-7 M carbachol with EC50 values of 5.1 μM and 0.78 μM, respectively. The maximal relaxant effects of Mirabegron are 94.0 % and 89.4% that of carbachol, respectively. Mirabegron is a time-dependent inhibitor of CYP2D6 in the presence of NADPH as the IC50 value in human liver microsomes decreased from 13 to 4.3 μM after 30 min preincubation. Mirabegron acts partly as an irreversible or quasi-irreversible metabolism-dependent inhibitor of CYP2D6.
in vivo: Mirabegron decreases primary bladder afferent activity and bladder microcontractions in rats. Mirabegron (0.3 and 1 mg/kg) inhibits mechanosensitive single-unit afferent activities (SAAs) of Aδ fibers in response to bladder filling. SAAs of C-fibers decrease only at 1 mg/kg Mirabegron treatment. Mirabegron administration suppresses the mean bladder pressure and the number of microcontractions during an isovolumetric condition of the bladder. Mirabegron is efficient on facilitation of bladder storage. Mirabegron dose-dependently decreases the resting intravesical pressure. Mirabegron dose dependently decreases the frequency of nonvoiding contractions, considered an index of abnormal response in bladder storage. Mirabegron exhibits no significant effects on the amplitude of nonvoiding contractions, micturition pressure, threshold pressure, voided volume, residual volume, or bladder capacity.

((plusmn))-Bisoprolol hemifumarate  Bisoprolol is a selective type β1 adrenergic receptor blocker.

Target: Adrenergic Receptor
Approved: July 31, 1992
Bisoprolol, on beta 1-adrenoceptor peptide induced autoimmune myocardial damage. In the animal model of autoimmune cardiomyopathy induced by active immunization of rabbits with beta 1-adrenoceptor peptide, bisoprolol was given at a dose of 3 mg/day throughout the study period. Our results showed high titer of anti-beta 1-adrenoceptor antibody in the immunized group throughout the study but not in the group receiving only bisoprolol [1]. Bisoprolol administration resulted in a significant reduction in HR reaching 60.3 +/- 1.4 bpm at VT of 500 mL (compared to 70.5 +/- 1.8 bpm with placebo, P < 0.001). Changes in HP were also significant with an increase in HP reaching 1004.5 +/- 22.2 msec at this controlled VT (compared to 860.3 +/- 21.5 msec with placebo, P < 0.001) [2].
Toxicity: Oral, mouse: LD50 = 100 mg/kg; Skin, rabbit: LD50 = 200 mg/kg; Skin, rat: LD50 = 500 mg/kg. Symptoms of overdose include congestive heart failure (marked by sudden weight gain, swelling of the legs, feet, and ankles, fatigue, and shortness of breath), difficult or labored breathing, low blood pressure, low blood sugar, and slow heartbeat.