Emetine amebicidal activity

It also has amebicidal activities that are due to its contained alkaloids. Emetine is much more active than cephaeline and less toxic, causing less nausea and vomiting than cephaeline. 

This drug has a direct amebicidal effect against trophozoites E. histolytica in tissues, and it is not active against cysts in either the lumen or intestinal walls, or in other organs. The mechanism of action of emetine consists of the blockage of protein synthesis in eukaryotic (but not in prokaryotic) cells. It inhibits the process of polypeptide chain formation. Protein synthesis is inhibited in parasite and mammalian cells, but not in bacteria. 

The efficacy of ipecac in amebic infections depends upon its content of alkaloids, the principal ones being emetine and cephaeline. Both are amebicidal, but emetine is much more active. Cephaeline is more toxic than emetine, except for the heart, and causes more nausea and vomiting. Emetine constitutes more than one half of the total alkaloidal content of ipecac. 

The monoterpene isoquinoline alkaloids are constituents of the genus Cephaelis and selected other Rubiaceae species. C. ipecacuanha (ipecac) is a powerful emetic whose active principle is emetine, derived through the condensation of dopamine and secologa-nin (Fig. 33). Emetine is also a powerful amebicide, antiviral, and inhibitor of protein synthesis. It is now largely replaced by synthetic dehydroemetine. 

Metronidazole given for 10 days is effective as monotherapy in many cases of hepatic abscess and has the dual advantage of being both amebicidal and active against anaerobic bacteria. However, treatment failures can occur and follow-up therapy with chloroquine is highly recommended. Luminal amebicides should also be given to eradicate intestinal infection. Treatment with emetine is contraindicated in patients with a history of cardiac disease. The answer is (D). 

The compound CL 75, 805 (VIII) is reported to have activity against both intestinal amebiasis in rats and hepatic amebiasis in hamsters, more potent than the other amebicides in general, except for emetine. From a series of 2-nitroimidazoles, non-specifically noted last year, one (IX) has been selected for extensive evaluation . ... 

---