[U.S. Food and Drug  Administration]

Clinical Therapeutics and the Recognition of Drug-Induced Disease

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Table 2:
Therapeutic Drug Monitoring


When prescribing drugs, keep in mind that pharmacokinetic variability means that one dose does not always fit all. Some adverse reactions are currently preventable by rational use of therapeutic drug monitoring (TDM), which individualizes doses by taking into account important patient variables. TDM is only of value in preventing reactions related to serum concentrations.

For certain drug classes, pharmacokinetic variability together with a narrow therapeutic index have led to a standard dosing strategy utilizing TDM to ensure safe use and avoid excessive toxicity, to the degree possible. Drugs that should be routinely monitored include digoxin, lithium, lidocaine, amino-glycosides, aminophylline, phenytoin, cyclosporine and tacrolimus.

Doses need to be individualized (adjusted up and down) to get patients within the desired therapeutic range. For many of these agents, clinical/laboratory monitoring of relevant pharmacodynamic endpoints is also recommended in conjunction with TDM (e.g., monitoring renal function in an aminoglycoside-treated patient.)

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