OBJECTIVE:Aspirin sustained release capsules(A-SRC) were prepared The release rate and bioavailability of A-SRC were studies METHODS:To study release mechanism by determining dissolution rate and to study relative bioavailability of A-SRC by determining serum concentrations in rabbits RESULTS:The release profile of A-SRC fitted zero-order kinetics This sustained release preparation had good release stability and high bioavailability in comparison with commonly-used aspirin sustained release capsules CONCLUSION:A-SRC showed obviously sustained release effect The drug concentration in blood kept steady and lasted long after oral administration,therefore the times of administration could be decreased Because the light-excipients were used in A-SRC,which had floating properties and could make drug release slowly A-SRC could decrease the irritations to gastrointestinal tract and other side effects