What is it?

Albendazole (Zentel) is an oral drug used to treat a variety of worm infections. It is related to mebendazole - a drug approved in the United States as Vermox. Albendazole is approved in several European and most Third World countries. The PWA Health Group helps import it from Mexico for PWAs with microsporidiosis. To obtain albendazole from the PWA Health Group, you must have a prescription from your doctor.


Microsporidiosis is a devastating, life threatening infection in people with AIDS. It can cause disease all over the body (lungs, eyes, etc), but it most often infects the gut and causes diarrhea. There is no proven treatment. In a number of uncontrolled studies, albendazole has reduced diarrhea.

Microsporidiosis is hard to diagnose. It can be hard to find even with an electron microscope or biopsy. There are new stool tests (spring, '95) which may help -- call us if you need further info. Many docs use albendazole empirically, meaning they use the drug to do the diagnosis. If the stool test is not conclusive, they'll give you albendazole. If your diarrhea gets better, bingo - the cause was microsporidiosis.

Treating diarrhea is tricky, but important to follow up on. If you have a diagnosis of microspordiosis, and albendazole doesn't, it could be because: 1) it can take up to 2+ months before the drug works, 2) there are different kinds of microsporidiosis, and albendazole works better with some than others (see below), or 3) other bugs are causing the diarrhea.


There is evidence from a couple of studies that people can have microsporidiosis and not have diarrhea or other symptoms. Some people who have test positive for microsporidiosis and have no symptoms, take albendazole as a way to prevent getting diarrhea. Albendazole has never been tested for microsporidiosis prophylaxis, so we have NO idea if this will work or not. In fact, we have no idea if everyone who has microsporidiosis will get diarrhea. It may be that many PWAs with microsporidiosis will never get sick from it.

Albendazole might cause problems if you are taking the protease inhibitor Norvir (ritonavir/Abbott). Talk to your doctor!!!!

Albendazole and Microsporidiosis

Albendazole works well for many people, but not for others. Why not? One - the drug is hard to absorb. It won't work if you don't have enough of it in your blood. Two - there are hundreds of kinds of microsporidiosis. Albendazole works really well against one called Septata. It works much less well against a more common kind called E. bieneusi.

The biggest clinical trial of albendazole so far included 29 PWAs with chronic diarrhea and weight loss. After taking 400 mg 2x/day for a month, their diarrhea improved and most people gained weight. Most people had E. bieneusi. Albendazole lowered the amount of parasites in some people, but it did not kill the infection in anyone with E. bieneusi. Another study of 19 PWAs taking the same dose reported that diarrhea completely stopped in 9 PWAs, and 3 others had 50% less diarrhea. Most studies and clinical practice report that diarrhea returns once you stop the drug.

Side Effects and Toxicity

A number of studies report that albendazole is well tolerated. Some PWAs report stomach aches. If taken at higher doses and/or for a long period of time, other side effects have been reported: elevated liver enzymes, headaches, hair loss, low levels of white blood cells (neutropenia), fever, and itching.

Albendazole causes birth defects in rats. Judging by how albendazole works, it would probably cause similar birth defects in people. Use birth control and avoid getting pregnant, or getting anyone pregnant, while taking this drug.


Doctors currently prescribe anywhere from 400 mg to 1600 mg twice a day, most commonly 1200 mg/day. Past studies used 400 mg 2x/day, but this dose did not work for everyone, and did not clear out the infection. The current American trial starts people at 800 mg 2x/day.

Higher doses seem to work better; people can respond to higher doses when lower doses haven't worked; and it can take up to two months for albendazole to work against E. bieneusi. Sadly, we have no data yet on combination therapy.

Other Potential Treatments For Microsporidiosis


In one study of 19 PWAs taking 500 mg of Flagyl 3x/day, 5 got better, and 10 got somewhat better. One month later, off drug, 12 PWAs had active microsporidiosis again. Biopsies showed that Flagyl didn't kill off the bug. A different study of Flagyl in PWAs with E. bieneusi had dismal results - the drug helped only somewhat with symptoms.


In a small study of 8 PWAs taking 750 mg 3x/day, Mepron lessened diarrhea in all 8 PWAs, on average 13 days after starting treatment. People gained an average of 9 lbs, but all four with E. bieneusi developed active microsporidiosis immediately when they stopped taking the drug.


Used as a last resort for a PWA with an undiagnosed eye infection, 200 mg 2x/day itraconazole cleared up what later tests showed to be microsporidiosis infection in the eye. Test tube studies have since shown that itraconazole interferes with the life cycle of microsporidiosis. Defeating E. Bieneusi will probably take a combo of drugs. An obvious combination is Mepron with albendazole, but this is only being studied in Europe. One test tube study suggested that itraconazole's effectiveness was greatly boosted with the addition of some unlikely drugs, like nifedipine (a calcium channel blocker). Other drugs and combinations currently under study in Europe are: albendazole + metromidazole (1500 mg/h); sulfadiazine 4g/h + pyrimethamine; Mepron 3000 mg/h; doxycycline 200 mg/h + nifuroxazide 1200 mg/h; itraconazole 400 mg/h; flubendazole 200 mg/h; chloroquine 300 mg/h; and paromomycin 3g/h.

Albendazole and Cryptosporidiosis

Albendazole has also been given to people with cryptosporidiosis in a small, uncontrolled study. It did not seem to help very much.

How Can You Get Albendazole?

There are three ways you can get albendazole: a free drug program from the company, a clinical trial, or from us.

Compassionate use

Your doctor can enroll you in a free, easier, compassionate use program run by Smith-Kline Beecham. You do not need a colonoscopy. Your doctor just needs to confirm that he or she believes that you have microsporidiosis. The company says they'll get drug to you within 3 weeks (down from 4-8 weeks in the past). The company is also working (spring 1995) with the FDA to waive the IRB approval process or arrange for a national IRB. To get enrolled, your doctor should call: (800)877-7074. A clinical trial offering drug or placebo (50-50 chance) is now enrolling across the country. After 4 weeks, everyone gets drug. Anyone who gets sicker during the trial will be switched over to drug. After the three months of the trial, everyone in the trial is rolled into the compassionate use program. There is a $100 reimbursement for participating in the trial. Finally, if you try to enter the trial, and don't qualify, you will be offered compassionate use.

This trial is critical if albendazole is ever going to get FDA approval as a treatment for microsporidiosis. Approval is the only way that this drug will get to the all the PWAs who need it. It is also critical for figuring out the uses and limitations of albendazole. To find out more about this trial, please call: 1/800-TRIALS-A. In New York, you can call Doug Dieterich's office at 212/986-3593.

What We Carry

We import Zentel brand albendazole from Mexico, made by SmithKline Beecham. It comes in boxes of 6 tablets 200 mg each. To order from us, you will need a prescription.