Biological medicines have transformed the treatment of inflammatory bowel disease, although original nonresponse and subsequent loss of response are prevalent, with negative consequences. Clinical investigations found a link between blood drug concentrations and the existence of antidrug antibodies and loss-of-response. Therapeutic drug monitoring (TDM), defined as the assessment of drug concentrations and antidrug antibodies, is emerging as a technique for optimising therapy and maximising the benefits of these medicines. TDM looks to be a viable technique in clinical practise, particularly in paediatric patients with marked variations in medication pharmacokinetics. 

The authors offer a review of the research on antitumor necrosis factor therapy optimization based on TDM tailored treatment techniques and potential strategies to recapture loss of response, including an algorithm for practical management.