Dr just gave me viladozone and told me to stop 20 mg daily buspar (buspirone). do I need to wait for buspar (buspirone) to clear from my system first? If so how long?

At least 24 hours. The half life of Buspar (buspirone) and it's active metabolite is 3 and 6 hours respectively. This means that very little will be present 24 hours after stopping it. There is a possible interaction between Buspar (buspirone) and viladozone so it's wise to wait at least 24 hours after stopping Buspar (buspirone) before starting Viladozone.