Betamethasone
Betamethasone. High-potency fluorinated synthetic glucocorticoid (~25× cortisol). Topical Class I-III strength depending on vehicle + ester… Oral half-life 8.1 h.
High-potency fluorinated synthetic glucocorticoid (~25× cortisol). Topical Class I-III strength depending on vehicle + ester form. Systemic IM/IV used for fetal lung maturation in preterm labor. Cushingoid risk with chronic high-potency topical use over large body areas.
ROUTES REORDERED so the dosing default is a solvable route. TD stays declared and remains the commonest use, but it carries no pk block: a topical corticosteroid’s systemic availability depends on vehicle, site and occlusion, so one scalar F would be a fiction. PO is authored and becomes the default. PK: three routes, three separate failures. The oral half-life of 8.1 h is verbatim and stands, but it was copied onto the intravenous row from a study comparing ORAL WITH TOPICAL dosing; the intravenous value is 6.5 h (PMID:6662164, eight healthy adults on a phosphate bolus). The intramuscular row cited a DEPOT product whose own paper gives 9.6 h for betamethasone and 80.8 h for the 17-monopropionate ester (PMID:21899210), so no single intramuscular half-life represents that product and 9.6 h is stored for the immediate species only; intramuscular F of 1 holds only for a phosphate-only solution (PMID:6487477), the same paper showing depot availability is much lower. THE TRANSDERMAL ROW CONTRADICTED ITS OWN CITATION: 5 h against a stated 16.6 h. All three volumes of 67 L are dropped — no abstract found states any numeric betamethasone volume — along with oral F 0.72 (from a paper with no intravenous arm) and both absorption rates, which sit beside stated peaks at 2.8 h.
Pharmacokinetics
- Oral — t½ 8.1 h
- IV — t½ 6.5 h · F 100%
- Intramuscular — t½ 9.6 h · F 100%
Sources: PMID:8148226, PMID:6662164, PMID:21899210, PMID:6487477