Misoprostol
Misoprostol. Synthetic prostaglandin E1 analog. Multiple uses: gastric mucosal protection (NSAID-induced ulcer prevention), labor induction… Oral half-life 0.5 h.
Synthetic prostaglandin E1 analog. Multiple uses: gastric mucosal protection (NSAID-induced ulcer prevention), labor induction, postpartum hemorrhage management, medical abortion (with mifepristone), missed miscarriage management.
PK: THE IMPOSSIBLE CLEARANCE WAS REAL, AND F WAS WHAT MADE IT IMPOSSIBLE. This record asserted a clearance near four times cardiac output, and the diagnosis is the opposite of what that suggests: an apparent clearance of that magnitude for misoprostol acid IS published — "apparent clearance 705 (431-1099) L/h or apparent volume of distribution 632 (343-1008) L", from a one-compartment fit, the same model shape this registry runs. It exceeds cardiac output because it is divided by an availability that is low and, for the circulating acid, unmeasurable. THE DEFECT WAS F 0.88, WHICH CONVERTED A PUBLISHED APPARENT VOLUME INTO A CLAIM ABOUT A REAL ONE — class 6 running in reverse — and its likely donor sits in this record own refs[]: a serum binding figure "between 81 and 89 %", which is the confirmed protein-binding-as-bioavailability shape. FIXING F ALONE WAS NOT ENOUGH: at F 1 with the old volume the implied clearance still sat above the published confidence interval, so both moved together. CAVEATS ARE RECORDED RATHER THAN BURIED: that population is labouring women at term dosed buccally and vaginally with nonlinear clearance and no oral arm, so its absorption rates are deliberately NOT transplanted, and its relative bioavailability figure is relative. The stored half-life remains an inequality bound, "less than 30 minutes", stored as exactly the bound. ANALYTE: the stored mass was the METHYL ESTER, and its own source says the ester is not there — "no unchanged drug is detected in the plasma or urine. The biologically active metabolite in the plasma is misoprostol acid (SC-30695)." The mass, the free fraction and every PK value describe the acid. The occupancy EC50 is corrected with it.
Pharmacokinetics
- Oral — t½ 30 min · F 100% · ka 4 h⁻¹ · Vd 632 L
Sources: PMID:11821273, PMID:15005878, PMID:9120826, PMID:35587540, PMID:3122274