[TDM (therapeutic drug monitoring) for dosing theophylline]

In order to maximize the effectiveness and safety of drug therapy, it is important to individualize the dosage of potent drugs. Some drugs can not be titrated against the intensity of the therapeutic or toxic actions. Determination of the blood concentration of such drugs can be a helpful guide in adjusting the dosage during their therapeutic use. The drug dosing guided by pharmacokinetics is called TDM or therapeutic drug monitoring. In conventional pharmacokinetics, a large number of blood samples are collected from one patient to determine the individual pharmacokinetic parameters. In TDM, the pharmacokinetic parameters obtained from a group of patients who belong to a certain category are used to guide estimation of the individual pharmacokinetic parameters and only a few blood samples from one patient are sufficient to determine the individual parameters. The blood concentration of a drug and the intensity of its pharmacodynamic action, however, is not necessarily correlated. Therapeutic decisions should never be based solely on the blood concentration of a drug.