CONTROLLED-RELEASE FROM A COATED PARTICLE - EFFECTS OF INITIAL CONDITIONS AND METHODS OF SOLUTION

The exact effects of three initial conditions - time lag, burst releas e, and steady state concentration profile - on drug release from a coa ted spherical matrix containing dissolved drug into a finite amount of well stirred elution liquid have been analyzed. The degree of the eff ect of initial conditions on drug release depends on the diffusivity r atio of coating layer to core matrix and the radius ratio of the coate d particle to the core. For the case where drug concentration in the c ore is dependent on time only, the differences between the exact and t he pseudo-steady state solutions are computed, therefore, pros and con s for the pseudo-steady state solution, which is simple and direct, ca n he anchored on exact comparison.