Hydroxyzine
Hydroxyzine. First-generation H1 antagonist with anxiolytic + sedating + antiemetic activity. Common alternative to benzodiazepines for anxiety… Oral half-life 20 h.
First-generation H1 antagonist with anxiolytic + sedating + antiemetic activity. Common alternative to benzodiazepines for anxiety due to no addiction potential. Anticholinergic burden — Beers-list problematic. Cetirizine is the active metabolite.
PK: A NEW DEFECT CLASS - VERBATIM-CORRECT AND STILL WRONG. The stored t-half of 3 h PASSED the contract: PMID:512901 says "the half-life of drug removal was approximately 3 hr", human, oral, 100 mg, healthy males, correct analyte. Four later human studies disagree by 2 to 12 times - "hydroxyzine about 20 hours", "20 to 25 hours", "29.3 +/- 10.1 hours" in the elderly, 7.1 h in children - because the 1979 assay truncated sampling below the terminal phase. THE PROOF IS PHYSICAL, NOT BIBLIOGRAPHIC: V 1200 L with a 3 h half-life implies a clearance of 277 L/h, or 4.6 L/min, WHICH EXCEEDS CARDIAC OUTPUT, against a measured 9.6 ml/min/kg = 40.3 L/h. A citation check can never reach this shape; only arithmetic can. AND THE ABSORPTION CONSTANT WAS THE INNOCENT PARTY: ka 2.0 with the old half-life predicts a peak at 1.22 h against a measured 2.0-2.3 h, but with the corrected 20 h it reproduces Tmax 2.00 h almost exactly, so it is kept and re-anchored. F 0.7 is removed and pinned to 1 - the only published bioavailability figure for hydroxyzine, 72%, is in SIX HEALTHY DOGS, and every human volume in the literature is apparent and per-kg, so an independent F would divide twice. Its H1 occupancy row is deleted separately.
Pharmacokinetics
- Oral — t½ 20 h · F 100% · Vd 1200 L
Sources: PMID:11809864, PMID:512901, PMID:2562944, PMID:6361228