Therapeutic drug monitoring (TDM)

One of the primary objectives facing the clinical pharmacokinetics is to maintain the optimal concentration of a medicinal product at the site of its action. This especially relates to drugs having narrow therapeutic range (some antibiotics, anti-arrhythmic drugs, cyclosporine, anticonvulsants, etc.). Currently, in Western Europe and the United States it is prohibited to assign some potent medicinal drugs (psychotropics, psychostimulants, antidepressants, etc.), medicinal drugs of prolonged use (antihypertensives, antiasthmatic, cardiostimulators) without control of the concentration in the blood of a patient. When assigning the drug to a patient the physician should solve two main problems of safe drug therapy: achieving a positive effect and avoidance the adverse effects when taking prescribed drugs. 

Such studies should be conducted in the following situations:

  • In case of significant interindividual variation of pharmacokinetic parameters of the drug, leading to substantial differences in specific values of steady-state concentrations in blood (it is especially important to be mindful to drug therapy in children who have significant differences in body mass and metabolic rate, gender differences also can not be ignored); 
  • In case of nonlinear kinetics of the drug there is no direct dependence between the dose of the drug and the concentration of drug in blood within the therapeutic level; 
  • In case of very narrow therapeutic range (the risk of adverse side and toxic effects); 
  • In case of specific cohort of patients (pregnant and lactating women, elderly people, infants, etc.), in which the pharmacokinetic parameters, and hence limits of safe therapeutic range, are significantly different from the usual well-known mean values; 
In case of dysfunctions of kidneys, liver or gastrointestinal tract, affecting the pharmacokinetic parameters; 
in polytherapy, when interaction of multiple drugs can not be excluded, and it is difficult to model the processes that lead to normalization of pharmacokinetic parameters; 
in case of doubt in regularity of the drug administration by the patient. 

  • carbamazepine 
  • phenobarbital 
  • phenytoin 
  • valproic acid
  • gentamicin 
  • tobramycin 
  • vancomycin
  • theophylline 
  • quinidine 
  • procainamide 
  • acetaminophen 
  • salicylates 
  • paracetamol 
  • tricyclic antidepressants
Cardiac glycosides: 
  • digoxin 
  • digitoxin 
  • cyclosporine.