<prompt> Therapeutic drug monitoring is required for all drugs except:PhenytoinMetforminTacrolimusCyclosporin  <response>: Therapeutic drug monitoring TDM is useful for digoxin, anticonvulsants, antiarrhythmics, theophylline, aminoglycoside antibiotics, lithium, tricyclic antidepressants. not useful for drugs whose response is easily measurable antihypeensives, hypoglycaemics Metformin, diuretics, oral anticoagulantsWarfarin, general anesthetics. Ref; KD Tripathi pharmacology 7th edition page no; 34 