Zafirlukast
Zafirlukast. CysLT1 receptor antagonist — same target as montelukast but BID dosing + meaningful CYP2C9 inhibition (raises warfarin INR).… Oral half-life 10 h.
CysLT1 receptor antagonist — same target as montelukast but BID dosing + meaningful CYP2C9 inhibition (raises warfarin INR). Hepatotoxicity warning; less prescribed than montelukast.
PK: only the half-life survives — "a mean terminal elimination half-life of approximately 10 hours in both healthy volunteers and patients with asthma" (PMID:11888331, a review). THE STORED F 0.6 WAS CONTRADICTED IN TERMS: the same abstract states "The absolute bioavailability of zafirlukast is unknown", and 0.6 was mis-derived from the very next sentence, that food "reduces bioavailability by approximately 40%" — a food effect turned into an absolute bioavailability. ka 0.5 /h traces to a ratio BETWEEN two rate constants ("Kac:Ka was <0.5", PMID:10751029), not to a rate. V 70 L appears nowhere. No absolute bioavailability or volume exists anywhere in the zafirlukast literature.
Pharmacokinetics
- Oral — t½ 10 h
Sources: PMID:11888331