<prompt> Therapeutic drug monitoring is required in all except:PhenytoinMetforminTacrolimusCyclosporine  <response>: Ans. B MetforminRef: KDT 8the p42 We can easily monitor blood glucose levels as an effect of metformin, thus TDM is not required. TDM is required for lithium, digitalis, phenytoin, immunosuppressants and anti-arrhythmics, etc. 