Hydroxyurea (brand name: Hydrea) has been on the market as an anti-cancer drug for over 30 years.  Initially, it was used to treat some types of leukemia, as well as ovarian cancer and sickle cell anemia.  However, it has recently been shown to have powerful anti-retroviral properties.  The results of initial testing in HIV infected patients have been very exciting.
 

• Administration:  Hydroxyurea is taken once daily by mouth, on an empty stomach.
• Indications:  Hydroxyurea is prescribed in some instances for leukemia, ovarian cancer, sickle cell anemia, and HIV.
• Side Effects: Skin rash, fever, chills, sore throat, mouth sores, bruising and bleeding, back pain.
• Contraindications: Pregnancy, anemia, infections (particuarly primary VZV infection), kidney disease.
• Mechanism:  Hydroxyurea alters the cellular enzyme ribonucleotide reductase which normally facilitates the formation of dNTP's.  Without the presence of this enzyme, HIV is unable to reverse transcribe its RNA to DNA.  Thus, Hydroxyurea reduces the viral load in some cases to levels which are undetectable.  There is some evidence that this effect may persist for the long term, even when anti-viral therapy is halted.  Additionally, Hydroxyurea penetrates the brain and lymph tissues, which may make it more effective than other anti-HIV drugs at preventing or treating HIV infection of the CNS.

A caveat:
    While this data is very exciting, it is not yet clear whether the anti-viral effects observed in vitro will be as profound in patients.  Most of the clinical studies conducted thus far had very small sample sizes and involved patients with low viral loads initially.  Finally, as Hydroxyurea suppresses T cell maturation, it is unlikely that this will be an effective treatment of patients with end-stage HIV infection.
 

For information that is slightly dated (1998-1999) but very thorough, see:
 http://www.thebody.com/treat/hydroxy.html
 

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