Therapeutic Drug Monitoring.pdf

Therapeutic Drug Monitoring Dr. Hrishikesh N. Gupta Assistant Professor, Government College of Pharmacy, Ratnagiri Therapeutic Drug Monitoring Basis for TDM: Intensity of pharmacological activity of any drug is better correlated with its serum concentration th...

Therapeutic Drug Monitoring Dr. Hrishikesh N. Gupta Assistant Professor, Government College of Pharmacy, Ratnagiri Therapeutic Drug Monitoring Basis for TDM: Intensity of pharmacological activity of any drug is better correlated with its serum concentration than with dose administered Definition - Determining the concentration of drug in the body fluids of patient and using it for designing the dosing regimen of the patient - Ensure the desired concentration of the drug in body for optimal and safe use Interindividual variations in drug disposition may lead to toxicity or treatment failure Useful for formulating individualized dosage regimen Drugs with narrow therapeutic index are candidates for TDM Digoxin, Phenytoin, Carbamazepine, Phenobarbital etc. Drug Candidates for TDM Narrow TI Small change in concentration of drug in plasma are likely to produce large change in response Drugs showing wide interindividual variations in the rate of metabolism Drugs exhibiting saturation kinetics, thereby causing steep relationship between dose and plasma levels within therapeutic range Drugs whose signs of overdosage and underdosage are difficult to distinguish Chronically used drugs more likely to induce toxicity or changes in pharmacokinetics Need of TDM When effect of the drug can not be assessed quantitatively by clinical observation Several drugs given concurrently and serious interactions are anticipated Replacement treatment (like thyroxine) is to be optimized When a non-compliance is suspected When a patient has concomitant disease that may alter drug disposition When patient’s condition is refractory to the dosage regimen Factors to be considered during TDM Patient data (Age, gender, lean body weight: Renal clearance) Dosage regimen (Dose, frequency, route, and duration: Steady state) Sampling time (short and long half lives) Indication for therapy (digoxin for atrial fibrillation and heart failure) Patient adherence (economic and dementia concerns) Reduced protein binding (phenytoin) Drug interaction (Polypharmacy, digoxin + amiodarone/ verapamil) Pathological factors (rifampicin, isoniazid in hepatic insufficiency) Tobacco use (Clozapine and theophylline) Alcohol use (chronic alcoholism induce metabolism) Medication sampling errors (TDM results become inconsistent) Laboratory errors (Repetition required) Indian Scenario for TDM TDM was introduced in India in 1980s Two types: - Clinical Pharmacology labs at large teaching hospitals - Clinical Biochemistry labs in private sector Clinical Pharmacology labs - HPLC technique: labour intensive, technically demanding and turnaround time is high - Clinical interpretation is done by experts Clinical biochemistry labs utilize automated equipment and ready to use kits - Fluorescence polarization and enzyme mediated immune assay techniques - High cost due to import of kits and storage conditions - No clinical interpretation of data Indian Scenario Collaboration for TDM with prescribers Expertise for Education and interpretation training to of data Pharmacist Prerequisites for TDM Awareness Identifying amongst the need for prescribers TDM Clinical lab testing facilities