OAR
See: Office of AIDS Research

Off-Label Use
Prescribed use of a medication for a condition other than one approved by the Food and Drug Administration (FDA), or for a patient population or at a dosage not approved by the FDA.

Office of AIDS Research (OAR)
The office within the National Institutes of Health's (NIH's) National Institute of Allergy and Infectious Diseases (NIAID) responsible for the scientific, budgetary, legislative, and policy elements of the NIH HIV/AIDS research program.

OHL
See: Oral Hairy Leukoplakia

OIs
See: Opportunistic Infections

Open-Label Trial
A clinical trial in which both the researchers and the participants know who is getting which drug or vaccine.
See Also:   Double-Blind Study

Opportunistic Infections (OIs)
Illnesses caused by various organisms that occur in people with weakened immune systems, including people with HIV/AIDS. OIs common in people with AIDS include Pneumocystis carinii pneumonia; cryptosporidiosis; histoplasmosis; toxoplasmosis; other parasitic, viral, and fungal infections; and some types of cancers.

Oral Hairy Leukoplakia (OHL)
A white-colored, hairy, or ribbed patch that appears on the side of the tongue and inside the cheeks. It develops mainly in people with weakened immune systems, including people with HIV. It is caused by Epstein-Barr virus (EBV), a member of the herpesvirus family.

Osteonecrosis
Also referred to as avascular necrosis. A medical condition in which bone tissue dies. Osteonecrosis affects some people with HIV, but it is unclear if it develops as a complication of HIV infection or as a side effect of anti-HIV drugs.
See Also:   Avascular_Necrosis

Osteopenia
A medical condition in which bones lose their minerals and become less dense, making them weaker and easier to break.

Osteoporosis
Severe loss of bone mass, density, and strength. Although usually an age-related disorder, osteoporosis may also occur as a result of HIV infection or as a side effect of anti-HIV drugs.