Core pharmacology

Class Group

H2 Receptor Antagonist

Legacy Cicm Level

-

Main Action

decreased gastric pH and decreased gastric secretions

Mechanism of action

MOA: Competitive antagonism of H2 receptors (high specificity) Histamine acts on GsPCR → increased AC → increased cAMP → increased protein kinase → increased activity of H/K antiporter

Physiological effects

GIT: Raised gastric pH. No effect on gastric emptying or LOS tone

CVS: Arrhythmias may occur after rapid injection (Cardiac H2-R)

Adverse Effects Toxicity

1. Porphyria
2. Thrombocytopenia and leukopenia
3. VAP

Absorption

Absorbed in small bowel
BA 50%

Distribution

Crosses BBB, placenta and breast milk

Protein binding

20% PB

Volume of distribution

Large Vd

Metabolism

50% Hepatic metabolism by CYP450

Excretion

50% excreted in urine unchanged

Half-life

T1/2= 1.5-2.5 hours