Luminal amebicides

Metronidazole plus a luminal amebicide is the treatment of choice for amebic colitis and dysentery. Tetracyclines and erythromycin are alternative drugs for moderate colitis but are not effective against extraintestinal disease. Dehydroemetine or emetine can also be used, but are best avoided because of toxicity. 

The treatment of choice for extraintestinal infections is metronidazole plus a luminal amebicide. A 10-day course of metronidazole cures over 95% of uncomplicated liver abscesses. For unusual cases in which initial therapy with metronidazole has failed, aspiration of the abscess and the addition of chloroquine to a repeat course of metronidazole should be considered. Dehydroemetine and emetine are toxic alternative drugs. 

Metronidazole or tinidazole is the drug of choice in the treatment of all tissue infections with E histolytica. Neither drug is reliably effective against luminal parasites and so must be used with a luminal amebicide to ensure eradication of the infection. 

Iodoquinol (diiodohydroxyquin) is a halogenated hydroxy-quinoline. It is an effective luminal amebicide that is commonly used with metronidazole to treat amebic infections. Its pharmacokinetic properties are poorly understood. Ninety percent of the drug is retained in the intestine and excreted in the feces. The remainder enters the circulation, has a half-life of 11-14 hours, and is excreted in the urine as glucuronides. 

Diloxanide furoate is a dichloroacetamide derivative. It is an effective luminal amebicide but is not active against tissue trophozoites. In the gut, diloxanide furoate is split into diloxanide and furoic acid about 90% of the diloxanide is rapidly absorbed and then conjugated to form the glucuronide, which is promptly excreted in the urine. The unabsorbed diloxanide is the active antiamebic substance. The mechanism of action of diloxanide furoate is unknown. 

Diloxanide furoate is considered by many the drug of choice for asymptomatic luminal infections. It is not available commercially in the USA, but can be obtained from some compounding pharmacies. It is used with a tissue amebicide, usually metronidazole, to treat serious intestinal and extraintestinal infections. Diloxanide furoate does not produce serious adverse effects. Flatulence is common, but nausea and abdominal cramps are infrequent and rashes are rare. The drug is not recommended in pregnancy. 

Amebiasis is generally treated with a combination of metronidazole [me troe NYE da zole] plus a luminal amebicidal drug, such as diloxanide furoate. This combination provides cure rates of greater than 90%. Metronidazole also has important antibacterial activity. 

Diloxanide often causes flatulence and, occasionally, nausea, vomiting, diarrhea, urticaria, and pruritus. It is an excellent luminal amebicide and is indicated after treatment with the 5-nitroimidazole compounds, which have relatively weak activity on the cyst stage. Experience over 14 years has been summarized by the Centers for Disease Control and Prevention (CDC, Atlanta), confirming the minimal toxicity of diloxanide. Fewer adverse effects were reported in patients aged 20 months to 10 years than in those aged over 10 years. There is no record of interactions between diloxanide and either metronidazole or tinidazole (SEDA-13, 830) (SEDA-17, 333). 

While standard recommendations are for 7—10 days duration of therapy, amebic liver abscess has been treated successfully by short courses (2.4 g daily as a single oral dose for 2 days) of metronidazole or tinidazole. E. histolytica persist in most patients who recover from acute amebiasis after metronidazole therapy, so it is recommended that all such individuals also be treated with a luminal amebicide. 

Tissue amebicides (chloroquine, emetines, metronidazole) act on organisms in the bowel wall and the liver luminal amebicides (diloxanide furoate, iodoquinol, paromomycin) act only in the lumen of the bowel. The choice of a drug depends on the form of amebiasis. For asymptomatic disease, diloxanide furoate is the first choice. For mild to severe intestinal infection, metronidazole is used with diloxanide furoate or iodoquinol. The latter regimen, plus chloroquine, is recommended in amebic liver abscess (Table 53-2). The mechanisms of amebicidal action of most drugs in this subclass are unknown. 

C. Iodoquinol Iodoquinol, a halogenated hydroxyquinoline, is an orally active luminal amebicide used as an alternative drug for mild-to-severe intestinal infections. Adverse gastrointestinal... 

Clinical use Metronidazole is the drug of choice in severe intestinal wall disease and in hepatic abscess and other extraintestinal amebic disease. Metronidazole is commonly used with a luminal amebicide. Other important clinical uses of metronidazole include treatment of trichomoniasis, giardiasis, and infections caused by Gardnerella vaginalis and anaerobic bacteria (Bfragilis, C difficile). 

E. Paromomycin This drug is an aminoglycoside antibiotic used as a second-line luminal amebicide. It may also have some efficacy against cryptosporidiosis in the AIDS patient. Adverse gastrointestinal effects are common, and systemic absorption may lead to headaches, dizziness, rashes, and arthralgia. Tetracyclines (eg, doxycycline) are sometimes used with a luminal amebicide in mild intestinal disease. 

Metronidazole plus a luminal amebicide is the treatment of choice in mild to moderate amebic colitis. Diloxanide furoate is commonly used as the sole agent in asymptomatic intestinal infection. The answer is (D). 

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). 

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