Approaches to the treatment of cytomegalovirus retinitis: ganciclovir and foscarnet

Article Abstract:

Cytomegalovirus (CMV) retinitis is an infection that causes inflammation of the retina. It can lead to blindness and is often seen in patients with AIDS. The antiviral drug ganciclovir is the only agent approved to treat this disease. Another drug, foscarnet, is presently being studied for this use. Ganciclovir inhibits viral replication by binding DNA polymerase, an enzyme necessary for DNA replication. To become activated, the drug must first be metabolized by the infected cell. Foscarnet also works by binding DNA polymerase, but does not need to be activated by the cell. Both drugs inhibit all human herpesviruses to some degree. Treatment of CMV retinitis with either drug initially requires high doses to completely inhibit viral replication and to allow the retina to repair. Because neither drug rids the body of CMV, maintenance therapy must be continued for an indefinite period of time to prevent recurrence. The two agents appear to be equally effective in preventing CMV retinitis from progressing during maintenance. The main difference between the drugs is in side effects. Ganciclovir can cause neutropenia, or low levels of white blood cells, which limits its use in a number of patients. Foscarnet can cause kidney problems and has similar limitations. It can also cause hypocalcemia, or low calcium levels in the blood, which can cause further serious effects. Drug treatment is not always a priority in patients with CMV retinitis. If the infection has not yet endangered functional vision, or if functional vision has already been destroyed, emergency drug treatment is unnecessary. When treatment is started, patients should be closely monitored for drug reactions and toxicity. Recent research indicates that ganciclovir and foscarnet might work better in combination. They act in slightly different ways and have completely different side effects. Taken together, lower doses of each drug might reduce side effects and increase the effectiveness of treatment for CMV retinitis. (Consumer Summary produced by Reliance Medical Information, Inc.)

Causes of, Physiological aspects, Ganciclovir, editorial, Neutropenia, Hypocalcemia

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Foscarnet therapy of cytomegalovirus retinitis in AIDS

Article Abstract:

Cytomegalovirus (CMV) infection may cause retinitis or inflammation of the retina, the inner lining of the eye; this is the most common cause of blindness in patients with acquired immunodeficiency syndrome (AIDS). The drug foscarnet was shown to inhibit viral deoxyribonucleic acid (DNA) polymerase, an enzyme involved in the formation of the viral DNA molecule which carries the genetic information of the CMV microorganism. Studies suggest that foscarnet may be effective in preventing the progression of CMV retinitis. The effectiveness of foscarnet was assessed in 17 patients with CMV retinitis. Foscarnet produced a complete response in eight patients, a partial response in eight patients, and no response in one case. The excretion of CMV in the urine was not decreased by foscarnet in 4 of 12 patients, despite improved retinal lesions. Adverse effects of foscarnet included: kidney failure, reflected by increased blood creatinine levels in 50 percent of patients and also the need for dialysis, the artificial filtration of the blood, in two patients; and anemia resulting in the need for blood transfusion in 10 patients. Among seven patients maintained on foscarnet therapy, four suffered recurrence of CMV retinitis, and only one remained in remission for longer than 24 weeks. The drug zidovudine did not worsen the incidence of side effects due to foscarnet use. Thus, foscarnet is effective in suppressing the activity of CMV in retinitis, although the suppression is not maintained. (Consumer Summary produced by Reliance Medical Information, Inc.)

Evaluation, Antiviral agents

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Treatment with letrazuril of refractory cryptosporidial diarrhea complicating AIDS

Article Abstract:

Letrazuril may have a short term effect in treating cryptosporidiosis in AIDS patients. Cryptosporidiosis is a severe diarrhea caused by a parasite which often causes or contributes to mortality in AIDS patients. An oral dose of 50 milligrams/day of letrazuril was given to 35 AIDS patients with cryptosporidiosis. Before treatment, 74% of the patients had five or more bowel movements a day, and 91% had watery bowel movements. Of the 35 patients, 12% did not respond to treatment, 63% experienced at least a 50% decrease in bowel movements per day, and 3% experienced a reduction to two or fewer bowel movements per day. The drug eradicated the parasite in 10 (40%) of 25 of the patients whose stools were tested. An average of 1.7 weeks of treatment caused a response among those whose condition improved. However, in 65% of the responders the disease relapsed an average of 1.2 months after treatment began. The major side effect was a rash which occurred in 20% of the patients and caused them to cease treatment.

Care and treatment, AIDS patients, Cryptosporidiosis

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