emetine

Emetine is a natural alkaloid of the ipecac family, primarily isolated from the root of ipecacuanha (Cephaelis ipecacuanha). Alongside cephaeline, emetine is one of the principal ipecac alkaloids. It has historically been used as an emetic and, at lower doses, as an antiparasitic agent against Entamoeba histolytica; in contemporary medicine its use is limited due to toxicity.

Mechanism and effects: Emetine inhibits protein synthesis by binding to the 40S ribosomal subunit, thereby blocking translocation during translation. This mechanism underlies both its antiparasitic activity and its cytotoxic risk to human cells. When used for antiamoebic therapy, it is typically given parenterally; oral administration can cause significant gastrointestinal irritation and systemic effects.

Safety and regulatory status: Cardiotoxicity is a major concern with emetine, including risk of myocardial injury and arrhythmias, along with potential myopathy, nephrotoxicity, and hepatotoxicity. Because of the narrow therapeutic window and severe toxicity, emetine-containing preparations are now rarely used and are generally restricted to controlled medical settings. Many countries discourage or regulate their use, and products for home use containing ipecac-derived emetine are no longer recommended.

Current practice: For amoebic infections, emetine has largely been supplanted by other agents such as nitroimidazoles (e.g., metronidazole), often combined with luminal agents to eradicate cysts. Emetine remains primarily of historical and pharmacology/toxicity interest, rather than as a first-line therapeutic option.