PROCEDURE:
In Vitro Microsome Study:
(1) The phosphate buffer protocol was used to prepare a buffer solution required for the experiment.

(2) Liver microsomes (human or rat) were incubated with the buffer solution, drug (simvastatin or pravastatin), and potential inhibitors according to the in vitro microsome protocol.

(3) Mixtures were analyzed using liquid chromatography and mass spectrometers to determine drug concentrations.

In Vivo Rat Study:
(1) 8 rats were separated into 3 groups and their blood was tested for concentrations of simvastatin according to the in vivo rat protocol.

(2) Collected plasma samples were prepared according to the plasma preparation protocol.

(3) A standard curve was prepared as a comparison for the plasma samples. Standard curve protocol.