Optimizing Individualized Dosage Regimens of Potentially Toxic Drugs

The end product of drug development is the use of the drug in clinical therapy. When a drug has a narrow margin of therapeutic safety, we must steer its dosage between one that is too low, and likely to be ineffective on the one hand, or too high, and likely to be toxic, on the other. We must carefully plan and individualize the dosage for each patient, to achieve some desired target goal such as a serum concentration, or its profile over time. We must then observe the patient, and if needed, monitor serum concentrations at appropriate intervals. These intervals should be frequent enough so we can evaluate the patient when there are relatively small changes in the total amount of drug in the body between observations, so that if toxicity develops, we detect it in an early stage of its development so we can make the appropriate adjustment in dosage early, rather than later, after toxicity has become more severe and dangerous.