Cefdinir
Cefdinir. Third-generation oral cephalosporin — extended gram-negative coverage; common for AOM + sinusitis + skin/soft tissue. Iron… Oral half-life 1.7 h.
Third-generation oral cephalosporin — extended gram-negative coverage; common for AOM + sinusitis + skin/soft tissue. Iron co-administration causes a non-pathological reddish stool (cefdinir-iron complex) — alarming but harmless.
PK: THE LARGEST ERROR IN THIS BATCH AT 24.5x, AND IT IS A DOUBLE DIVISION. The cited paper supports only three quantities — "the Tmax, Cmax and T1/2beta of cefdinir and cefpodoxime after oral administration of 100 mg were 2.5 h +/- 0.48 h, 0.81 mg/L +/- 0.19 mg/L, 1.73 h +/- 0.3 h" — and states no volume, clearance or bioavailability at all. The stored pair gave an effective apparent volume of 1167 L and a clearance of 476 L/h FOR A RENALLY CLEARED BETA-LACTAM, more than five times hepatic blood flow. Against a verbatim "AUC(0-12) ... 10.3 +/- 1.35 micrograms.hr/ml" the model produced 0.42. CLASS 6 IS PROVABLE HERE RATHER THAN INFERRED: cefdinir has NO INTRAVENOUS FORMULATION, so an absolute bioavailability cannot have been measured and any published volume must be apparent. The replacement is triangulated two independent ways — from that exposure and from the peak — landing on the same apparent volume within 7%, and it reproduces both to within 5%. A NEAR-MISS IS RECORDED SO NOBODY TAKES THE OBVIOUS SHORTCUT: 245 is exactly ten times the textbook 24.5 L, a tempting dropped-decimal story, BUT AT 24.5 L THE RECORD IS STILL 2.45x LOW — the defect is the double division, not a lost decimal point. Its own Tmax of 2.5 h also exceeds the one-compartment ceiling its own half-life implies.
Pharmacokinetics
- Oral — t½ 1.7 h · F 100% · Vd 48 L
Sources: PMID:15631795, PMID:8222489