Emetine

# Overview
Emetine is a drug used as both an anti-protozoal and to induce vomiting.  It is produced from the ipecac root.

# Early emetine-based preparations
Early use of emetine was in the form of oral administration of the extract of ipecac root, or ipecacuhana.  This extract was originally thought to contain only one alkaloid, emetine, but was found to contain several, including cephaeline, emetine, psychotrine and others.  Although this therapy was reportedly successful, the extract caused vomiting in many patients which reduced its utility.  In some cases, it was given with opioids to reduce nausea.  Other suggestions to reduce nausea involved coating the drug to allow it to be released after digestion in the stomach.

# Use of emetine as anti-amoebic
The identification of emetine as a more potent agent improved the treatment of amoebiasis.  While use of emetine still caused nausea, it was more effective than the crude extract of ipecac root.  Additionally, emetine could be administered hypodermically which still produced nausea, but not to the degree experienced in oral administration.
Although it is a potent anti-protozoal, the drug also can interfere with muscle contractions, leading to cardiac failure in some cases.  Because of this, in some uses it is required to be administered in a hospital environment so that adverse events can be addressed.

# Development of dehydroemetine
Dehydroemetine is a synthetically produced drug similar to emetine in its anti-amoebic properties, but it produces fewer side effects.  In the United States, it is manufactured by Roche and distributed by the Center for Disease Control on a compassionate use basis as an investigational drug for the treatment of metronidazole-resistant amoebiasis. 
Some examples of the use of dehydroemetine in the treatment of amoebic infections include:
- In 1993, the successful treatment of cutaneous amoebiasis in a 7-year old girl with dehydroemetine and metronidazole in Mexico. 
- A double-blind study of oral dehydroemetine in the treatment of amoebiasis performed at St. Mary's Hospital, Catholic Medical College, Seoul, Republic of Korea in 1973-1974 showed that dehydroemetine treatment was effective.  A total of 60 patients were treated, 20 with dehydroemetine, 20 with Tiberal, and 20 with metronidazole.  25% of patients treated with dehydroemetine reported adverse reactions, compared to 20% with other drugs, but no patient discontinued therapy due to the reaction.  In all three cases, the drug therapy resulted in clearance of the infection, defined as negative results through an O&P exam, in all but 1-2 patients.
- A 1979 study of 27 patients treated with dehydroemetine and various other drugs suggested that all drug combinations were successful at treating amoebic liver abscesses. 
- A 1986 in-vitro study compared the effects of dehydroemetine, metronidazole, ornidazole, and secnidazole on Entamoeba histolytica.  Metronidazole was found to be most effective, and the other three drugs were of similar effectiveness. 

# Dehydroemetine therapy in other diseases
A 1980 report described the use of dehydroemetine in treatment of herpes zoster, a condition which can produce painful neurological symptoms.  The study involved 40 patients, all of whom were over 60, and compared dehydroemetine treatment to another drug.  The study reported patients treated with dehydroemetine experienced relief of neuralgia with no changes in cardiovascular functions. 
Dehydroemetine has been investigated as a treatment for Leishmania infection.