Therapeutic drug monitoring

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Therapeutic drug monitoring (TDM):

Therapeutic drug monitoring (TDM) Amol Pramod Muthal, Gokhale Education Society , Sir Dr. M.S. Gosavi College of Pharmaceutical Education and Research, Nashik – 422 005


Introduction TDM: is defined as the use of drug concentrations in body fluids as an aid to management of patients receiving drug therapy for the cure, alleviation or prevention of disease. It is a tool that can guide clinicians to provide effective and safe drug therapy in the individual patient.


Objective To attain rapid and safe concentration of drug in plasma within the desired therapeutic range in order to provide the safest approach to optimal drug therapy. To coordinate clinical pharmacology, pathology, chemistry, toxicology, analytical chemistry and medicine. To remove empirical trial and error approach.

NECESSITY OF TDM Which drugs required monitoring?:

NECESSITY OF TDM Which drugs required monitoring? Pharmacokinetic variability e.g. aspirin, digoxin . 2. Conc. related therapeutic and adverse effects e.g. phenytoin: ataxia , vertigo, drowsiness 3 . Narrow TI: digoxin 4 . Effect difficult to monitor. 5 . Inter individual variations in metabolism. 6 . Saturation kinetics: omeprazole 7 . Difficult to recognized toxicity clinically: cyclosporin , Seizures 8 . Hepatic and renal diseases: aminoglycosside 9 . Multiple drug therapy and drug interaction, Probenicid increases level of penicillin 10 . Doubtful patients compliance.


DRUG EXAMPLES • Antibiotics : Aminoglycosides • Antiepleptics : Phenytoin, carbamazepine • Cardiac drugs: Digoxin, amiodarone • Psychotherapeutics: Lithium, tricyclic AD • Miscellaneous: Theophylline, Methotrexate


TDM NOT NECCESSARY • Broad range of doses • Direct measurement of response • No correlation between plasma concentration and clinical response • Expensive procedure 


PRINCIPLE EFFECTIVE TDM 1. Continuous and graded response 2 . Residual pharmacodynamic variability 3 . Accurate dosing a ) Correct sampling site and time b ) No error during administration c ) Rugged and accurate means of analysis

TDM Process:

TDM Process 1. Decision to request Any toxicity? Lack of response Assessment of compliance Assess therapy after regimen change Potential drug interactions Chronic administration needed. 2 . Patient demographics 3 . Time of sample withdrawal 4 . Collection of biological sample 5 . Laboratory measurement

Patient demographics:

Patient demographics • Patient information • Patient age • Address, occupation, reference • Indication for TDM • Precipitation factor, etiology, other illness • Treatment past, present, other • Investigations

Laboratory measurement:

Laboratory measurement • Specific methods 1. Colorimetry 2 . UV-spectrometry 3 . Fluorescence spectrometry 4 . Chromatography Gas chromatography HPLC HPTLC SFC 5 . Capillary electrophoresis

Laboratory measurement:

6. Immunoassay i ) RIA ii ) Enzyme Immunoassay: a ) ELISA: Enzyme linked immunoassay b ) EMIT: Enzyme multiplies immuno -technique c ) FPIA: Fluorescence polarization d ) NIIA: Nephelometric inhibition 7 . LC-MS: Least count mass spectrometry Laboratory measurement


MONITORING PARAMETERS: EG DIgoxin The following patient parameters should be monitored during digoxin therapy: – Digoxin serum level - Obtain level within 24 hours of digitalization, weekly until stable , and at steady state. – BUN and serum creatinine Measure every two days, or every day in unstable renal function. – Weigh patient daily. – Measure and monitor urine output daily – Monitor pulse daily. • Therapeutic serum concentrations The usual digoxin therapeutic range is 0.8 to 2 ng /ml. • Precautions - Proper timing of serum sampling is critical. Serum samples should be drawn just prior to the daily dose and after six hours after administration of the drug.


ADVANTAGES OF TDM • Side effect monitoring • Short hospital stay • Better disease control • Dose adjustment • Doses guideline • Individualized dose requirement • Usefulness to clinical pharmacist


CONCLUSION • TDM is required for effective patient care management • It leads to optimizing pharmacological therapy • Decreased incidence of drug/ drug related toxicity and decreased disease exacerbation • Reduced hospital stay • Avoidance of unnecessary medication • Decreased side effects • It is reliable, valuable and efficient tool of patients compliance and management of therapy in patients receiving complex co medication or suffering from other diseases.

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