Hydroxyurea is a 30 year old anticancer drug that may help certain anti-HIV drugs work better. Researchers have been studying hydroxyurea in people with HIV for several years now, with some promising results.

How does hydroxyurea work? DNA is inside all your cells. DNA is the basic building block of all living things, including the instructions to make more cells. HIV uses the DNA in your cells to make more HIV. DNA is made up of nucleotides. Hydroxyurea works by reducing the number of nucleotides inside cells, making it harder for HIV to make more viruses. In fact, hydroxyurea reduces the amount of one particular type of nucleotide, called adenine. When hydroxyurea is used alone it doesn't affect HIV very much. HIV still has enough adenine nucleotides to choose from to build its DNA and make more HIV. This is where other anti-HIV drugs come into the picture.

The nucleoside analog anti-HIV drugs -- AZT, ddI, ddC, d4T, and 3TC -- block HIV by acting as fake nucleotides. ddI (Videx) acts as a fake adenine nucleotide. When hydroxyurea is taken with ddI, fewer natural adenine nucleotides are left in the cell for HIV to steal when making DNA. With fewer adenine nucleotides, it becomes more likely that HIV will use the fake adenine nucleotide provided by ddI. If HIV uses the fake adenine nucleotide, it's more likely to make DNA that doesn't work. If the DNA doesn't work, then the HIV can't take over the cell.

Study results. Several small studies have reported that taking hydroxyurea with ddI produces a stronger anti-HIV effect than taking ddI alone. These studies also suggest that adding hydroxyurea to ddI can work against HIV that is resistant to ddI.

A large international study compared a triple drug combination of hydroxyurea, ddI and d4T (Zerit) to double combinations of either ddI and d4T, ddI and AZT, or ddI and hydroxyurea. Results showed the triple drug combination to be more effective in reducing viral load. About 75% of participants taking hydroxyurea, ddI, and d4T had undetectable viral loads of less than 400 copies of HIV after six months of treatment.

Average T4 cell counts were around 350 at the start of the study and went up an average of 30 cells in the triple therapy group. Researchers think that the small T4 cell count increase is because hydroxyurea blocks the production of new cells. In people with over 200 T4 cells this small increase may not be a problem. Other studies clearly show that serious infections are rare when the T4 cell count stays above 200. For people with lower counts, hydroxyurea should be used with caution. Detailed information on these and other studies is available by contacting The Network at (800) 734-7104 .

Side Effects. The side effects of hydroxyurea depend on the dose, and happen more often at the higher doses used in cancer chemotherapy. The major side effect of hydroxyurea is suppression of the bone marrow. Bone marrow suppression can show up on laboratory tests as low red blood cells (anemia), low white blood cells (neutropenia, leukopenia), thrombocytopenia (low platelets) or as low numbers of all types of cells (pancytopenia). For people already having bone marrow problems, hydroxyurea is not recommended.

Less frequent side effects include hair loss, anorexia, nausea, vomiting, diarrhea and constipation. Rashes, particularly on the face, have also been reported. Hydroxyurea has been shown to cause birth defects in animals and should not be taken by pregnant women.

Dosage. Most studies use 500 mg of hydroxyurea taken twice a day. One study tried a lower dose of 500 mg once a day, and even this low dose seemed to help ddI work better than ddI alone. If side effects are a problem, the lower dose is worth considering. Resistance is not an issue with hydroxyurea, as it is with other anti-HIV drugs.

Hydroxyurea as salvage therapy. Salvage therapy is for someone who's used up all their treatment options. Caution should be used in using hydroxyurea in people with advanced HIV, low T4 counts and extensive treatment history because of its toxicity. In a recent salvage study, half the participants got anemia (low red blood cells) and needed blood transfusions or treatment with bone marrow stimulants. Neutropenia (low white blood cells) was also a problem in this study. One person experienced bone marrow failure and there were two deaths.

Hydroxyurea is available by prescription. Bristol Myers-Squibb is one of the main manufacturers of hydroxyurea (trade name Hydrea) and has set up a patient assistance program for people who need help accessing the drug. The program can be reached at (800) 272-4878.

The Simple Facts Project is a program of The Network. If you need help finding out whether or not a specific drug or therapy is covered by private or public insurance, contact The Network at (800) 734-7104. This information does not intend to promote or endorse any specific treatment for any health related condition.

Simple Facts indexNetwork home page

Last modified: 8/31/98 The Network copyright © 1998 The Network