Alfentanil
Alfentanil. Synthetic μ-opioid agonist — phenylpiperidine class. ~⅕ fentanyl potency but faster onset (~1 min) and shorter duration. Used for… IV half-life 1.5 h.
Synthetic μ-opioid agonist — phenylpiperidine class. ~⅕ fentanyl potency but faster onset (~1 min) and shorter duration. Used for short surgical procedures + rapid analgesia. CYP3A4 substrate (DDI with strong inhibitors).
PK: IT PASSES ITS ARITHMETIC ONLY BECAUSE ITS HALF-LIFE IS MISATTRIBUTED. The volume is verbatim in the cited paper; the half-life IS NOT IN THAT ABSTRACT, which says "97 +/- 52 minutes" — 1.617 h, not 1.5. The 1.5 comes from a different paper already carried in this record references, whose control arm ALSO supplies the clearance the record is then checked against, so the pass is partly circular. Numbers untouched, provenance stated. A CONFLICT IS RECORDED AND NOT RESOLVED: the stored fraction unbound of 0.093 disagrees 1.9-fold with this record own intravenous source, which reports "fu was 0.18 +/- 0.08". An intramuscular route declared with no parameters at all is removed, as is a phantom absorption constant on an intravenous one. DOSE: THE STORED FIGURE WAS THE RAW PER-WEIGHT NUMBER, NOT A DOSE — 5–50 mcg/kg, entered as flat milligrams. The dose unit enumeration has no weight-based member and the solver never weight-scales a dose, so THE ONLY REPRESENTABLE FORM IS THE SEVENTY-KILOGRAM EQUIVALENT, and that is what this record now carries. I TESTED THE OBJECTION THAT THIS READS A SCHEMA GAP AS A DATA DEFECT AND THE DISTINCTION IS CLEAN: vancomycin stores the seventy-kilogram equivalent of its weight-based regimen and is CORRECT, meropenem is genuinely flat-dosed and is CORRECT, and eleven records store the raw per-weight number and are WRONG BY ROUGHLY SEVENTY-FOLD. Both of my priors on the two correct records were wrong. EFFECT COMPARTMENT: THE OLD VALUE WAS GENUINELY FITTED, WHICH IS NOT THE SAME AS BEING THE RIGHT ONE. It came from a five-subject COMPARATOR arm whose reported spread is 67 percent of its own mean, and it ran 1.6-fold fast against the definitive head-to-head — the same abstract that supplies the remifentanil correction in this batch, so both opioids now come from one cohort measured the same way.
Pharmacokinetics
- IV — t½ 1.5 h · F 100% · Vd 33 L
Sources: PMID:17112806, PMID:1729938, PMID:8638836