Therapeutic drug monitoring (TDM) refers to the
measurement and interpretation of principally blood or plasma drug
concentration measurements to optimize a patient’s drug therapy and clinical
outcome while minimizing the risk of drug-induced toxicity. TDM involves
tailoring a dosing regimen to a patient by maintaining the plasma
or blood concentration within a particular range. To achieve optimal drug therapy 3 objectives should be met:
• To attain the desired
pharmacological effect of the drug.
• To reach the maximal
effect in the shortest possible time.
• To decrease the risk of
toxicity.
Therapeutic drug monitoring (TDM) is helpful in
drugs:
• With a narrow
therapeutic index.
• Which is highly protein bound.
• Which are liable to
interact.
• In which the metabolite
might be toxic.
Role of Pharmacist in TDM:
A reliable and responsive TDM service depends on teamwork
between nurses, doctors, pharmacists, scientists, and technical staff. The
clinical pharmacist should provide advice to medical staff on the appropriate
use and timing of TDM and assist with the interpretation of results. In
addition, the pharmacist may be involved in:
• Initial selection of drug regimen. This may involve decisions about drug choice, dose, dosing interval, route of administration, and dosage form of the drug, taking into account factors such as sex, age, body weight, race, metabolism status, renal function, plasma albumin concentration, use of other drugs and laboratory results.
• Adjustment of the dosage
regimen based on TDM results and the patient’s clinical response.
• Assessment of possible
causes for unexpected results, such as non-compliance, bioavailability problems, medication errors,
drug interactions, or pharmacogenetic variability.
• Dose adjustment for
patients on hemodialysis or peritoneal dialysis.
• Provision of poison
information.