Protection of travelers against Hepatitis A viral infection in developing countries.

To the Editor: Giaudia lamblia is a common intestinal protozoa, leading to longstanding intestinal complaints in many of those infected. Chronic symptoms may occur intermittently and may be florid or subtle. Diagnosis can often be confirmed by well-performed stool examinations or with an enzyme immunoassay (EIA) to detect G. lamblia fecal antigen. Even after these, as well as other invasive procedures, some cryptic G. lamblid cases cannot be parasitologically confirmed. In patients with strong epidemiological and clinical evidence of giardiasis, marked improvement and apparent cure may be obtained after empiric treatment with anti-Giardia drugs.' Failure to consider giardiasis, or inability to confirm a parasitologic diagnosis and reluctance to empirically treat, deprive those with cryptic chronic giardiasis of the opportunity to be cured with a simple, safe, and inexpensive treatment regimen. To treat giardiasis, there are presently only two commercially available drugs in the United States: metronidazole (Flagyl) and furazolidone (Furoxone). Other nitroimidazole drugs, including tinidazole (Fasigyn) and ornidazole (Tiberal), have been found effective in other countries but are unlicensed in the United States. Paromomycin (Humatin), an FDA approved drug, has had variable effectiveness in studies in other countries, primarily in infected children.* Metronidazole is currently considered the treatment of choice for giardiasis in the United States, (though never approved by the FDA for this indication). Cure rates ranging from 85 to 95% have been reported and it is generally well-tolerated in a course of 250 mg three times a day for 7 days.3 Furazolidone has as its major indication in the United States the treatment of giardiasis. I t tomes in a liquid formulation, making it particularly useful for young children. Reported cure rates range from 75 to 84% and certain troublesome side effects may O C C U ~ . ~ Quinacrine (Atabrine) is the most effective drug against giardiasis, with reported cure rates of 92-95%.' Quinacrine was withdrawn from the market by the manufacturer (Sanofi Winthrop) and it is unavailable commercially worldwide. Quinacrine remains an FDAapproved drug and some pharmacies have been compounding quinacrine USP powder into 100 mg gelatin capsules. Quinacrine treatment should be attempted in the approximately 10% of cases of proven or strongly suspected giardiasis not responding to other available drugs. A rare case of parasitologically proven giardiasis not responding to any of these drugs alone may be cured with a combined course of metronidazole and q~inacr ine .~ In our experience, numerous individuals with suspected but unproven giardiasis and nonresponsive to available drugs have obtained marked and continuous improvement only after treatment with quinacrine. We are unaware of known beneficial effect of quinacrine on any other infectious or noninfectious diarrheal illness. Quinacrine is not free of side effects, and one of us has reported a 1.5% incidence of toxic psychosis with the formerly used 7 day course of 100 mg three times a day.' More recently, using a five day course, no toxic psychosis cases have been seen. Quinacrine has an important role in treating recalcitrant and cryptic giardiasis and efforts should be made to again have it readily available in all pharmacies.