Rev Med Chil. 1992 May;120(5):539-44.  

[H2 antagonists as inhibitors of cytochrome P-450 in rat liver: in vitro and in
vivo effects]

[Article in Spanish]

Carrasco M, Gaule C, Vega P, del Villar E.

Servicio de Medicina Interna, Hospital Regional de Copiapo.

Cytochrome P-50 is a well known participant in the metabolism of xenobiotics as
well as an activator or inactivator of hepatotoxic substances and carcinogenic
agents. H2 antagonists, cimetidine, famotidine and ranitidine were used to
inhibit cytochrome P-450 in rat liver. After 200 mg cimetidine, 85% inhibition
of cytochrome P-450 in vitro and 50% in vivo were demonstrated through
demethylation of aminopyrine. Inhibition was further confirmed by differential
absorption spectra (Type II). The percentage inhibition obtained with famotidine
or ranitidine were lower than those obtained with cimetidine. Inhibition of the
microsomal oxidative system by cimetidine could lead to decreased production of
superoxide radicals and protection against damage induced by toxic agents
activated in the liver.

PMID: 1364175 [PubMed - indexed for MEDLINE]