Kinetics of total octreotide remaining (A), native octreotide content (B) and divalent cation remaining (C) after incubation of PLGA microspheres in PBST at 37°C. ■ Formulation 1, no additive was added to organic phase; ▲Formulation 2, adding 25 mg NaCl to organic phase; ▼Formulation 3, adding 25 mg CaCl2 to organic phase; and ✩Formulation 4, adding 25 mg MnCl2 to organic phase