Mirabegron
Mirabegron. β3-adrenergic agonist — relaxes detrusor smooth muscle without anticholinergic side-effect burden. Preferred over oxybutynin /… Oral half-life 20 h.
β3-adrenergic agonist — relaxes detrusor smooth muscle without anticholinergic side-effect burden. Preferred over oxybutynin / tolterodine in elderly. CYP2D6 inhibitor — caution with metoprolol, antidepressants. Modest BP elevation.
PK: CLASS 12 AT 2.46x, AND A WORKED EXAMPLE OF WHY F MUST NOT MOVE ALONE. Its cited paper states none of the four values; the real donor, absent from refs[], gives all of them: "Mean half-life was around 40 h for both routes of administration. Volume of distribution at steady state was 1,670 l and total clearance was around 57 l/h for i.v. dosing." The stored volume is verbatim and INTRAVENOUS, so class 6 is acquitted — but pairing that bi-exponential steady-state volume with a terminal half-life asserts a clearance of 23.2 L/h against the measured 57. RAISING F TO THE 50 mg FIGURE, AS I ORIGINALLY PROPOSED, WOULD HAVE MULTIPLIED EXPOSURE BY A FURTHER 1.21 AND TURNED 2.46x INTO 3.0x. Instead the half-life becomes the mono-exponential equivalent that honours both verbatim intravenous numbers, disclosed as derived rather than quoted. The stored F is verbatim but is the 25 mg value while this record typical dose is 50 mg, and the 35% figure I asserted for 50 mg IS NOT VERBATIM ANYWHERE — that abstract jumps from 25 mg to 150 mg — so it is deliberately not stored. ka 0.6 predicted a peak at 6.4 h against "peak plasma concentrations were attained after ~ 4 h". A modelling compromise is recorded: mirabegron is dosed as a controlled-absorption tablet, so a first-order absorption rate is an approximation of a designed release profile.
Pharmacokinetics
- Oral — t½ 20.3 h · F 29% · ka 0.83 h⁻¹ · Vd 1670 L
Sources: PMID:25791612, PMID:22943933