A medication that decreases or ceases cocaine use potentially improves adherence at clinic appointments as well as adherence to medication. In addition, it might indirectly decrease the progression of the disease. Ondansetron, a serotonin type 3 receptor antagonist (5HT3), at 4mg twice a day has been shown to have a greater rate of improvement in percentage of participants with a cocaine-free week compared to placebo in cocaine dependent non HIV infected treatment seeking individuals. (Johnson, B.A. 2006)