"In many cases in dealing with experienced patients who have been on multiple treatments, there is a tendency to settle for less than optimal results," said Scott Hammer, professor of medicine at Columbia University, New York.

"But we now have new protease inhibitors and other drugs that are specifically designed to overcome viral resistance. We now think that, even in very experienced patients -- those who have been unable to keep the virus undetectable by the most sensitive assays after being on three or four regimens -- we can get 60 percent or more of these patients to suppress the virus to undetectable," he told United Press International.

Infection with human immunodeficiency virus (HIV) -- the virus that causes AIDS -- is incurable, but by using potent antiretroviral drugs in combinations, doctors can suppress the virus to such low levels that, not only is it undetectable in the blood, but the virus has difficulty in replicating itself, lessening the chance that it can mutate to escape the drugs.

Patients who remain faithful to their treatment regimens now can live decades with the virus.

The guidelines, which appear in this week's special AIDS-theme issue of the Journal of the American Medical Association (JAMA), was released in conjunction with the week-long 16th International AIDS Conference in Toronto, Canada, which has drawn more than 26,000 scientists, activists, doctors, journalists and other allied health care professionals.

It is the largest of the conferences in terms of attendance since the meetings were first held in 1985.

Hammer, the lead author of the guidelines, said the approval of the protease inhibitor tipranavir (Aptivus) and darunavir (Prezista), also known as TMC114, have the ability to overcome multidrug resistance. In the past, clinicians have been satisfied to keep the virus at reduced, if not undetectable levels, in patients who had exhausted treatment options.

Aptivus and Prezista were developed to specifically attack resistant virus.

"Now," Stefano Vella, director of drug research and evaluation for Italy's national health agency in Rome, told UPI, "we are telling doctors that they should go for 'a home run' and treat these patients with resistant virus with these new drugs in hopes of suppressing the virus to undetectable levels once again."

He said that by including the newer agents in the second- and third-line treatment, undetectable virus can be achieved in most of these so-called "salvage" patients.

Vella and Hammer were part of the worldwide team of HIV/AIDS experts who updated the guidelines of the International AIDS Society, USA, a San Francisco-based organization that is independent of the similarly-named International AIDS Society, the sponsor of the Toronto gathering.

Vella told UPI the other changes in the guidelines are subtle in nature. "We are telling doctors that they probably should begin treating patients sooner, before their level of CD4-postive cells falls below 200," he said.

CD4-positive cell counts are a crude marker of how well a patient's immune system is doing. In HIV infection, the virus invades the host's immune cells and converts them into factories that mass-produce the virus. The takeover of the immune cells leaves the host defenseless against common bacterial infections that cause pneumonias, diarrhea, cancers and other diseases.

These opportunistic infections are the symptoms of AIDS, and it is these infections that can be fatal. The new guidelines suggest treating patients when CD4-positive cells are in the 200 to 350 cell range.

The new guidelines also are telling doctors that intensive testing to ensure drug levels are being maintained in the blood stream and the viral load in the blood are under control may not need to be done as frequently as before, Vella said.

"These drugs now are very good and are producing consistent results," Vella said. "We are letting doctors know they may be able to relax a bit in this area."

The international experts reviewed published, peer-reviewed literature on HIV/AIDS to come up with the new guidelines, which counsel doctors on when to begin treatment, what medications to use for initial therapy, when to change the treatment regimen, and what new regimen to choose.

The regimen for initial treatment is also essentially unchanged -- a combination of two nucleoside reverse transcriptase inhibitors and either a protease inhibitor or a non-nucleoside reverse transcriptase inhibitor.

The favored non-nucleoside reverse transcriptase inhibitor is Sustiva (efavirenz), but there are a range of choices for the protease inhibitor and the nucleoside reverse transcriptase inhibitors, Hammer said. "The choice is really up to the provider," he said, taking into account the patient's history.

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