Cimetidine

pharmacological · digestive · Oral · IV

Cimetidine. H2 receptor antagonist — first H2 blocker to market; suppresses gastric acid via H2 → cAMP → parietal cell. Inhibits CYP1A2, CYP2D6… Oral half-life 2 h.

H2 receptor antagonist — first H2 blocker to market; suppresses gastric acid via H2 → cAMP → parietal cell. Inhibits CYP1A2, CYP2D6, CYP3A4, CYP2C9 — substantially raises levels of theophylline, warfarin, phenytoin, propranolol. Largely supplanted by famotidine (no CYP DDI).

PK: half-life 2 h and oral F 0.6 are both verbatim in the PO row cited review, PMID:6418428 ("Elimination half-life is approximately 2 hours"; "The absolute bioavailability in healthy subjects is about 60%"). The IV row cites the primary behind the disposition figures, Larsson 1982 (PMID:7059413), 9 patients with normal renal function. V 70 L is retained as the review 1 L/kg scaled to 70 kg and is flagged as derived rather than quoted. ka 2 /h dropped as a DIGIT COLLISION with the 2 h half-life, and it could not be right in any case: the same abstract reports that "2 plasma concentration peaks are frequently observed", which no single first-order absorption rate can represent. PERPETRATOR CAVEAT: this record drives other compounds interaction curves, and its 2 h holds only at normal renal function — the same primary gives 3.1 h at moderate and 4.5 h at severe impairment. INTERACTIONS: ALL FOUR AFFINITIES ARE THE SAME INVERSION THROUGH AN ASSUMED 5.0 µM, and each reconstructs its own cited figure to better than one percent — including two edges whose sources report a CLEARANCE FALL rather than an exposure rise, converted correctly as the reciprocal. THE ASSUMED CONCENTRATION IS THREE TIMES THIS RECORD OWN MODELLED MEAN, though it sits below the modelled peak, so the calibration is anchored nearer the peak than the average. Declared.

Pharmacokinetics

Related compounds

Sources: PMID:6418428, PMID:6322709, PMID:6786672, PMID:2878667, PMID:6096071, PMID:9663842