A study by researchers at the National Institutes of Health (NIH) indicates that a steroid medication taken with an HIV protease inhibitor may increase the risk of bone damage in HIV-infected patients.

The drug interaction may also increase the risk of Cushing’s syndrome, a hormonal disorder caused by prolonged exposure of the body's tissues to high levels of steroids.

Published in the Dec. 15 issue of the Journal of Acquired Immune Deficiency Syndrome, the study showed that ritonavir, a protease inhibitor used to treat HIV patients, taken with the corticosteroid medication, prednisone, significantly increased the concentrations of prednisolone — the active form of prednisone — in the systems of healthy volunteers.

“Physicians have noted bone lesions on scans of HIV patients treated with steroids for inflammation,” said Dr. Scott Penzak, NIH Clinical Center pharmacist and lead author of the study. “We wanted to find out if the problems might be at least partially explained by an interaction between the steroids and HIV drugs.”

Corticosteroids are used to provide relief for inflamed areas of the body. They lessen swelling, redness, itching, and allergic reactions. They are used to treat a number of conditions, including severe allergies, skin problems, asthma, and arthritis.

Researchers gave ten healthy volunteers a 14-day course of low-dose ritonavir. They also gave the volunteers three doses of prednisone. One dose of prednisone was given before ritonavir was started as a baseline. A second dose was given after four days on ritonavir and a third dose was given after 14 days on ritonavir. Blood samples were taken after each dose of prednisone to determine steroid levels.

Prednisolone concentrations were 41 percent higher than the baseline amount after the drugs were taken together four days into the ritonavir regimen and 30 percent higher after the drugs were taken together 14 days into the regimen.

“These are statistically significant increases,” said Penzak. “They indicate that when the drugs are taken together, steroid concentrations in the body may rise to levels that cause side effects in some individuals.

“These results serve as a caution to clinicians treating HIV patients on concurrent steroid therapy,” said Penzak. “They may choose to start with lower steroid doses or increase their level of toxicity monitoring compared to steroid recipients who are not taking protease inhibitors.”

“It is these small steps that advance the safe practice of medicine,” said Dr. John Gallin, director of the NIH Clinical Center. “Through continued clinical research, we can improve the health of all Americans.”

The study team included researchers at the NIH Clinical Center and the National Institute of Allergy and Infectious Diseases.

The team plans to continue studies of the blood levels of individuals on steroids and other HIV medications.

The NIH Clinical Center is the clinical research hospital of the National Institutes of Health. Through clinical research, physicians and scientists translate laboratory discoveries into better treatments, therapies and interventions to improve the nation's health.

NIAID is a component of the National Institutes of Health, an agency of the U.S. Department of Health and Human Services. NIAID supports basic and applied research to prevent, diagnose and treat infectious diseases such as HIV/AIDS and other sexually transmitted infections, influenza, tuberculosis, malaria and illness from potential agents of bioterrorism. NIAID also supports research on transplantation and immune-related illnesses, including autoimmune disorders, asthma and allergies.

The National Institutes of Health (NIH) — The Nation's Medical Research Agency — includes 27 Institutes and Centers and is a component of the U. S. Department of Health and Human Services. It is the primary Federal agency for conducting and supporting basic, clinical, and translational medical research, and it investigates the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit http://www.nih.gov.