Chlorpheniramine
Chlorpheniramine. First-generation H1 antagonist — common OTC component of multi-ingredient cold/allergy products. Sedating + anticholinergic… Oral half-life 28 h.
First-generation H1 antagonist — common OTC component of multi-ingredient cold/allergy products. Sedating + anticholinergic burden. Less drowsy at low dose than diphenhydramine.
PK: A CITATION TRANSPLANT WITH THE DONOR IDENTIFIED. PMID:11332874, a nasal-spray relative-bioavailability study, states NONE of the five stored numbers - its entire numeric content is Cmax, AUC and four ratios. Every value instead tracks Huang 1982, a proper adult intravenous-plus-oral study that was never cited: "Mean t 1/2 from 7 oral fasting studies in 5 subjects was 28 h". F 0.41 IS A CROSS-ARM AVERAGE, and the arithmetic is exact: the source reports "Absolute bioavailability from oral solution (10 mg) was 59 and 34%, and from tablets (8 mg) 44 and 25%", whose four-way mean is 40.5%. It becomes 0.34, verbatim from a review - "about 0.34 for chlorpheniramine" - which is also close to the tablet-only arms this record doses. ka 0.7 IS A NEW COLLISION SHAPE: IT IS THE ABSORPTION LAG TIME. The same sentence reads "Mean absorption lag time was 0.7 h (0.4-1.3 h), and mean peak time was 2.8 h", and 0.7 per hour predicts a peak at 4.9 h against that measured 2.8. V 230 L is IV-derived at 3.2-3.6 L/kg, so CLASS 6 IS ACQUITTED. MY PREDICTION THAT THIS RECORD WOULD HAVE TO BE SKIPPED WAS WRONG - the literature is thin only if you read the wrong paper. DOSE MOIETY: THE SIBLING OF THE BROMPHENIRAMINE CASE, AND THE SAME ARITHMETIC. Doses are the maleate; the molecular weight and the pharmacokinetics are the free base. Note this record stores a real measured bioavailability against a true intravenous-derived volume, so unlike its sibling nothing else on it moves.
Pharmacokinetics
- Oral — t½ 28 h · F 34% · Vd 230 L
Sources: PMID:11332874, PMID:7106172, PMID:2866055