Anti-Diarrheal Drugs

Treating, Recognizing Diarrhea

Reprinted from Positive Living, a publication of AIDS Project Los Angeles, pp 4, 5, & 16, by Peter George

Diarrhea, defined as more than three loose or watery stools daily, can be a problem for people with HIV infection.

At least 50 percent of people with HIV in the United States develop some diarrhea during their course of disease. Manifestations of disease in the gut have only recently become apparent because people are living longer due to improvements in prophalaxis and treatment strategies. Research efforts for the development of vaccines to treat hiv-associated diarrhea may involve IgA, the major antibody naturally produced along the lining of the gastrointestinal (GI) tract for protection.

Early Site of Infection

The GI tract is one of the earliest major sites of HIV infection. Several studies link chronic diarrhea and weight loss with shortened survival. Malabsorption, wasting and malnutrition can be caused by diarrhea. In 50 to 80 percent of AIDS cases with diarrhea, a responsible pathogen can be identified. Theses organisms may include various bacterial, viral, mycobacterial or protozoal parasites. Because many of the different types of diarrhea are not very susceptible to our currently approved drugs, only about half of this group can be successfully treated. Treating an organism may only partially eliminate the symptoms.

Apart from specific organisms, diarrhea may be due to the indirect effects of HIV. Acute diarrhea can be a one-time incident that lasts a few days, several weeks or even months. All forms of diarrhea lead to poor absorption of vital nutrients that the body utilizes to remain healthy.

Recent travel, medications and diet (especially the ingestion of foods containing lactose, and enzyme in dairy products such as milk, to which many people with HIV are intolerant) should be considered when evaluating an AIDS patient with diarrhea. The number and frequency of bowel movements may assist in the confirmation of which part of the GI tract is most affected. Large volume, relatively infrequent, or nocturnal diarrhea suggests small bowel (intestine) disease. Frequent, bloody bowel movements with abdominal pain and rebound tenderness suggestive of colon disease (large intestine).

Stool studies -- the next step in evaluation -- should include tests for all bacterial pathogens, standard ova and parasites, Clostridium difficile toxin, and Cryptosporidium parvum. Samples are usually screened with an acid-fast staining technique. If fevers are also present, blood cultures, chest radiography, and urinalysis should be performed. Sometimes bacteria may appear in the blood and not in cultures.

An endoscopy is suggested if stool samples have tested negative. Sometimes D-xylose testing is used to help distinguish between upper and lower GI disease. An abnormal D-xylose test is consistent with malabsorption and would suggest that an upper endoscopic biopsy be performed. People with classic signs of small bowel disease should have and upper endoscopy with a small bowel biopsy. A colonoscopy is recommended if the history of the person suggests colitis. Some physicians opt for sigmoidoscopy first, and then colonoscopy if the biopsies are negative. If it is unclear which area of the gastrointestinal tract is affected, or which procedure is necessary, then both procedures should be performed.

In the case of unrevealing test outcomes, symptomatic therapy with non-specific antidiarrheal medications such as loperamide, diphenolxylare, paregoric, or opium are often successful. Parenteral treatment with octreotide, and lactose-free, low-fat diets may also be helpful. If malnutrition is a problem, enteral or parenteral nutritional therapy may be effective. If no enteric pathogen is identified and diarrhea persists after six to eight weeks, then the diagnostic evaluation should begin again and include several stool tests and endoscopic biopsies. Pathogens are often identified if the diagnostic cycle is repeated.

Common pathogens isolated from small bowel (intestine) include: Cryptosporidium parvum, Microsporidium, Isospora belli, Mycobacterium avium complex (MAC), Salmonella species, Campylobacter species, Giardia lamblia, or HIV. Large-bowel isolated pathogens may be: CMV, Cryptosporidium parvum, NAC, Shigella group D, Clostridium difficile, Campylobacter jejuni, Histoplasma capsulatum, Adenovirus, Herpes simplex, Pneumocystis (rare), or HIV.

Pathogens vary geographically, seasonally, and by behavior risk factor; therefore, frequency and prevalence of each pathogen are difficult to judge. Almost all people with HIV will be lactose intolerant and may consume large amounts of milk in an attempt to gain weight. Drugs such as ddI, pentamidine, and other drugs can cause pancreatitis, which can lead to steatorrhea (fat in the stool). The effectiveness of treatment is a separate issue.