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To evaluate the bioavailability of exemestane (EXM) from self-micro emulsifying drug delivery systems (SMEDDS) and suspension formulations, a sensitive, specific, and rapid liquid chromatography-mass spectrometric method was developed and validated. The analyte was extracted from plasma samples and detected by mass spectrometry (MS) with an atmospheric pressure positive-ion chemical ionization (APCI) mode using a heated nebulizer interface. Progesterone (PGS) was used as the internal standard. A Hychrome RPB-L428 column was used to perform the chromatographic separation, the mobile phase being methanol and 15 mM ammonium formate (80:20). The MS detection used a heated nebulizer interface, with multiple reaction monitoring (MRM) operated in positive-ion mode. Both, EXM and PGS were well-separated and identified by their relative retention times, that is, 1.13 and 1.84 min, respectively. After oral administration of EXM loaded SMEDDS and suspension formulation to rats, a significant difference was observed in the pharmacokinetic behavior of drug in both the formulations, and a 2.9-fold increase in the relative bioavailability of EXM was observed with the SMEDDS as compared with suspension formulation. The developed method was found to be suitable for bioanalysis of exemestane and, hence, successfully depicted the bioavailability enhancement of exemestane SMEDDS in Wistar rats. [ABSTRACT FROM AUTHOR]