Fexofenadine
Fexofenadine. Second-generation H1 antagonist — active metabolite of terfenadine (pulled from market for QT). No CNS sedation; no QT signal.… Oral half-life 3.8 h.
Second-generation H1 antagonist — active metabolite of terfenadine (pulled from market for QT). No CNS sedation; no QT signal. P-glycoprotein substrate (grapefruit juice lowers F).
PK: F 0.33 IS AN INEQUALITY BOUND — "at least 33%" — and an absolute bioavailability for this drug does not exist: "not known because of a lack of studies of intravenous administration of this agent". F is therefore pinned to 1 and the volume stored as apparent, derived within the cited paper own placebo arm from its exposure and half-life. V 80 L was a template shared with five unrelated compounds. The half-life of 3.75 h is verbatim but is SAMPLING-WINDOW-LIMITED: the literature spans 3 to 17 h, and the drug shows flip-flop from slow absorption of a zwitterion. A SCALAR BIOAVAILABILITY IS NOT DEFENSIBLE ANYWAY — grapefruit juice alone moves exposure 2.8-fold. Both this record only reference and its receptor source are a TERFENADINE analogue paper: fexofenadine is terfenadine active metabolite, so the provenance is anchored to the parent drug rather than to this molecule. ka 1 dropped, the registry modal default appearing on 43 records.
Pharmacokinetics
- Oral — t½ 3.8 h · F 100% · Vd 163 L
Sources: PMID:19660947