Buspirone hydrochloride (Buspar) is a drug that stimulates receptors for 5-hydroxytryptamine, which is prescribed as an anti-depressant. It has been shown to have a direct effect on levels of cyclic adenosine monophosphate (cAMP) in T-lymphocytes, and it has been theorised that the drug may have an immunomodulatory effect in HIV infection^[1].

A pilot study found that when buspirone was administered at a dose of 15mg a day rising to 60 mg a day, all ten recipients showed sustained increases from baseline in CD4 cell counts, proliferative capacity of peripheral lymphocytes, and sustained decreases in HIV viral loads^[2]. However, a randomised study of buspirone in 23 HIV-positive patients failed to show any changes in CD4 cell counts, although the drug did cause increases in CD8 T-cell counts and the ratio of CD4 to CD8 T-cells^[3].