8th March 2019, Volume 132 Number 1491

Afrasyab Khan, Arvenia B Berahmana, Andrew S Day, Murray L Barclay, Michael Schultz

The incidence of inflammatory bowel disease (IBD) in New Zealand has risen substantially in the last five decades.1–6 IBD comprises Crohn’s disease (CD) and ulcerative colitis (UC) with a small…

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Various medications are available for the treatment of inflammatory bowel disease. The effective use of these medications is important and leads to better outcomes. Monitoring the level of medications and/or their breakdown products (therapeutic drug monitoring) in a patient’s blood can lead to more effective and individualised dosage recommendations. These blood tests are available in New Zealand. Therapeutic drug monitoring can decrease the risk of drug toxicity and help in decision making for further treatment if one therapy seems to be failing. This document represents the New Zealand Society of Gastroenterology Guidelines on Therapeutic Drug Monitoring in Inflammatory Bowel Disease.


The incidence of inflammatory bowel disease (IBD) in New Zealand has increased over the last several decades. The management of IBD has been transformed since the introduction of monoclonal antibody drugs. Other medications used in the treatment of IBD include amino-salicylates, steroids, thiopurines and methotrexate. Therapeutic drug monitoring (TDM) involves the measurement of serum drug levels or active metabolites and anti-drug antibodies. TDM is essential for a personalised approach to the management of patients with IBD and is used to optimise drug efficacy and reduce the risk of toxicity. In IBD, TDM can be used for checking adherence, evaluating drug toxicity, identifying hypermethylators, assessing loss of response and in decisions regarding treatment escalation or de-escalation. Management decisions in patients on a thiopurine are facilitated by checking TPMT enzyme activity and thiopurine metabolite levels. Measurement of drug trough levels and anti-drug antibodies can result in individualised treatment decisions in patients on biologics. In addition to using TDM in patients who fail therapy, proactive TDM can potentially facilitate early treatment decisions, albeit more work is needed in this area. The clinical benefits of reactive TDM are well documented and this has been shown to be cost effective. Studies have shown that combination therapy in patients on a biologic leads to better clinical outcomes. Effective use of drugs in the treatment of IBD is even more imperative in the New Zealand setting due to relatively fewer options of funded treatment, and the limitations on the use of available drugs. This document represents the current guidelines of the New Zealand Society of Gastroenterology on TDM in IBD.

Author Information

Afrasyab Khan, Gastroenterology Advanced Trainee, Gastroenterology Unit, Southern District Health Board, Dunedin; Clinical Lecturer, Department of Medicine, University of Otago, Dunedin;
Arvenia B Berahmana, Trainee Intern, Gastroenterology Unit, Southern District Health Board, Dunedin; Andrew S Day, Professor, Department of Paediatrics, University of Otago, Christchurch; Murray L Barclay, Professor, Department of Medicine, University of Otago, Christchurch; Department of Gastroenterology, Christchurch Hospital, Christchurch; Michael Schultz, Associate Professor, Gastroenterology Unit, Southern District Health Board, Dunedin; Department of Medicine, University of Otago, Dunedin.


Michael Schultz, Associate Professor of Medicine (Gastroenterology), Department of Medicine, University of Otago, PO Box 56, Dunedin 9054.

Correspondence Email


Competing Interests

Dr Day reports personal fees from Abbvie and Janssen outside the submitted work.


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