Postexposure chemoprophylaxis: approval criteria for clinical trials

Article Abstract:

Presently, zidovudine (AZT) is the only drug approved and available for directly treating infection with the human immunodeficiency virus (HIV), the agent that causes AIDS. It is now mainly used in HIV-infected individuals who have shown evidence that their immune systems are deteriorating. Whether the drug might be useful in preventing infection in persons exposed to the virus before infection is diagnosed has not been studied. This is a particularly important issue for health care workers who come into contact with infected bodily fluids. Many health care workers are exposed to such materials, but the rate of infection among this population is very low. Decisions on using AZT to prevent infection would have to weigh type of exposure, likelihood of infection, side effects of the drug, and possible benefits of drug treatment. Clinical trials using drugs for postexposure prevention need to set standards for what will determine successful trials. A number of different standards could easily satisfy the requirements established by the government to determine whether a drug can go on the market. One standard involves only showing that the drug works against HIV with little emphasis on side effects. AZT fits this category. Such a trial seems beneficial to patients with little hope, but the risks most likely outweigh the possible benefits for healthy people with little chance of infection. A second standard involves applying risks and benefits found in one population to another. This leads to similar problems as the first standard. In the third standard, the one used for most drugs, a study using a treated group and a placebo group is conducted. Because of the severe results of HIV infection, these types of studies are now problematic because pressure to treat all individuals at risk is great. A fourth type of study would give the drug at different times after exposure, eliminating a no-treatment group. If earlier treatment gave greater protection from infection, drug effectiveness would be indicated. A final standard would compare two drugs individually and in combination, so that all subjects would receive some treatment. All types of studies are acceptable for different situations and risks versus benefits need to be weighed before choosing the best one. (Consumer Summary produced by Reliance Medical Information, Inc.)

Health aspects, Drugs, Testing, Risk factors, editorial

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Postexposure chemoprophylaxis with ZDV or ZDV combined with interferon-alpha: failure after inoculating rhesus monkeys with a high does of SIV

Article Abstract:

Health care workers can be accidentally exposed to the human immunodeficiency virus, usually through needlesticks or other contact with contaminated blood. It is not known whether antiviral drugs given immediately after exposure might prevent infection. Although no proof exists that postexposure treatment can prevent the development of disease, many hospitals offer treatment with zidovudine (ZDV) to their workers who have been contaminated. ZDV is used to treat HIV infections, as it inhibits the virus from multiplying and slows the time to the development of symptomatic disease. Three cases have been reported that indicate that postexposure administration of ZDV does not prevent infection. However, in two of the cases the amount of contaminated blood the patients were exposed to was extremely high. The effectiveness of the procedure is difficult to test in humans. Therefore, rhesus monkeys were used as an animal model to test postexposure treatment with either ZDV alone or ZDV combined with interferon-alpha (a compound that stimulates the immune system) given three hours after the monkeys had been exposed to high does of the simian immunodeficiency virus (SIV), a strain which is closely related to HIV and causes a disease similar to AIDS. Neither treatment prevented infection after exposure to a high level of virus. The combined treatment with ZDV and interferon-alpha led to reduced levels of one of the viral proteins that was tested for, possibly indicating that the replication of the virus was slightly reduced. No differences were seen in survival rates. Therefore, the administration of ZDV or ZDV and alpha-interferon does not appear to be an effective treatment to inhibit infection after exposure to HIV. (Consumer Summary produced by Reliance Medical Information, Inc.)

Evaluation, Occupational diseases, AIDS (Disease), Interferon alpha

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Simian immunodeficiency virus infection via amniotic fluid: a model to study fetal immunopathogenesis and prophylaxis

Article Abstract:

Injecting simian immunodeficiency virus (SIV) into the amniotic fluid of pregnant rhesus monkeys may represent a cost-effective model for studying transmission of human immunodeficiency virus (HIV) from mother to infant. The transmission rate of HIV from mother to infant ranges from 25% to 30%, and infection appears to occur during childbirth following exposure to skin or mucous membranes. Both SIV and HIV are genetically close and replicate in a similar manner. Fetal skin and mucous membranes come into direct contact with amniotic fluid, and the fetus also swallows it. SIV was directly injected into the amniotic fluid of seven pregnant rhesus monkeys, and six of the fetuses were born infected. Six of the mothers also became infected. Both mothers and infants showed signs of disease such as weight loss and low birth weight and lymph disorders although none developed AIDS in 17 months of follow-up. The high rate of mother-to-infant transmission seen in this animal model may be useful for studying the prevention and treatment of AIDS in children.

Models, Causes of, HIV infection in children, Pediatric HIV infections, Disease transmission

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