Valproic acid is a low intrinsic clearance drug. A decrease in the average C_ss without an accompanied decrease in pharmacologic effect suggests that the free concentration did not change. This is seen with protein binding displacement interactions with low intrinsic clearance drugs. As the f_up increases, the CL_H increases, resulting in a decrease in C_ss. However, free C_ss remains unchanged. Thus, pharmacologic effect should not change

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