<prompt> Therapeutic drug monitoring is done for;PhenytoinHeparinAspirinMetformin  <response>: Therapeutic drug monitoring is adjustment of dose of the drug according to its plasma concentration. It is required for A Aminoglycosides e.g. gentamicin Drug Digitalis Possessing Phenytoin anti-epileptics Low Lithium Therapeutic Tricyclic antidepressants Index Immunomodulators e.g. cyclosporine Criteria for doing TDM Low therapeutic index When therapeutic response cannot be easily measured Inconsistent pharmacokinetics of the drug. 