(1) Dose deviation due to administration error.
(2) Nonlinear pharmacokinetics (Nonlinear PK).
(3) High bioavailability and individual variability in the DMPK properties of the drug, with IV and PO, given to different groups of animals.
(4) Overestimation of PO AUC or underestimation of IV AUC due to unreasonable sampling points.
(5) IV samples were left for extended periods, and compounds were unstable in plasma.
(6) When administered as a racemate, the faster-clearing enantiomer is converted to the slower-clearing enantiomer in the GI tract.