Therapeutic monitoring of plasma level of drug is done when using all of the following drugs except:

Therapeutic drug monitoring (TDM) is useful in the following situations: 1. Drugs with low safety margin-digoxin, anticonvulsants, antiarrhythmics, theophylline, aminoglycosides, lithium, tricyclic antidepressants, vancomycin In case of failure of response without any apparent reason-antimicrobials, To check patient compliance-psychopharmacological agents Monitoring of plasma concentration is of no value for1. Drugs whose response is easily measurable antihypeensives, hypoglycaemics, diuretics, oral anticoagulants(Warfarin), general anesthetics.2. Drugs activated in the body-levodopa.3. 'Hit and run drugs' (whose effect lasts much longer than the drug itself)-reserpine, guanethidine, MAO inhibitors, omeprazole.4. Drugs with irreversible action-organophosphate anticholinesterases, phenoxybenzamine. ref ; KD Tripathi pharmacology 7th edition (page no; 34)