a - Diseases that affect the function of the eliminating organs can significantly alter the rate of drug elimination. (e.g. the decrease in kidney function causes significant decrease in the rate of gentamicin elimination resulting in higher gentamicin concentrations)

b - The physiological changes associated with diseases can affect the distribution and elimination of drugs. (e.g. patients with congestive heart failure have decreased cardiac output and decreased liver blood flow which decrease the rate of hepatic elimination of drugs such as lidocaine)