Emetine

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Chapter: Essential pharmacology : Antiamoebic And Other Antiprotozoal Drugs

It is an alkaloid from Cephaelis ipecacuanha. Emetine is a potent and directly acting amoebicide—kills trophozoites but has no effect on cysts.


EMETINE

 

It is an alkaloid from Cephaelis ipecacuanha. Emetine is a potent and directly acting amoebicide—kills trophozoites but has no effect on cysts. It acts by inhibiting protein synthesis in amoebae by arresting intra-ribosomal translocation of tRNA-amino acid complex.

 

The stool in acute dysentery is rapidly cleared of the trophozoites and symptomatic relief occurs in 1–3 days (even faster than metronidazole), but it is not curative in the sense that the patient continues to pass cysts in the stool. It is highly efficacious in amoebic liver abscess also.

 

Emetine cannot be given orally because it will be vomited out. It is administered by s.c. or i.m. injection: 60 mg OD. It should be given only till acute symptoms subside; not more than 10 days in any case. It is concentrated in liver, kidney, spleen and lungs. Emetine is very slowly excreted in urine taking 1–2 months. Thus, a second course should not be repeated within 6 weeks, otherwise cumulative toxicity can occur.

 

Toxicity of emetine is high.

 

Local: It is an irritant; pain, stiffness and eczematous lesions occur at the site of injection.

 

Nausea and vomiting are frequent. After parenteral administration this is central in origin due to stimulation of CTZ. Vomiting due to oral dose of emetine is primarily because of gastric irritation.

 

Abdominal cramps and diarrhoea due to emetine toxicity may be confused with that due to intestinal amoebiasis itself.

 

Weakness and stiffness of muscles; a myositis like picture may be present.

 

Hypotension, tachycardia, ECG changes and myocarditis are the most serious complications. To avoid these, strict bed rest must be imposed during emetine therapy and exercise should be prohibited for another 1–2 months.

 

Emetine is contraindicated in presence of cardiac or renal disease and during pregnancy.

 

Use

 

Because of the above drawbacks, emetine is now seldom used as a reserve drug in severe intestinal or extraintestinal amoebiasis, or for patients not responding to or not tolerating metronidazole. A luminal amoebicide must always follow emetine to eradicate the cyst forming trophozoites.

 

It is also effective in liver fluke infestation.

 

EMETINE HCl: 60 mg /2 ml inj.

 

Dehydroemetine

 

It is a semisynthetic derivative of emetine; equally effective but less cumulative and less toxic to the heart. Thus, it is preferred over emetine by most physicians.

 

Dose: 60–100 mg s.c./i.m.OD for not more than 10 days.

 

DEHYDROEMETINE HCl: 30 mg/ml inj, 1 and 2 ml amps.

 

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