Varying concentrations of tyrosine kinase inhibitors in chronic myeloid leukemia patients following bariatric surgery: a case series.

Bariatric surgery is increasingly performed to treat severe obesity. As a result of anatomical and physiological changes in the gastrointestinal tract, the pharmacokinetics (PK) of oral drugs can be altered, affecting their efficacy and safety. This includes the class of tyrosine kinase inhibitors (TKIs) which are used to treat chronic myeloid leukemia (CML). This case series describes the clinical course of four CML cases with a history of bariatric surgery. The patients used various TKIs (nilotinib, dasatinib, bosutinib, ponatinib, and imatinib) for which 15 drug levels were measured. The measured TKI concentrations were in part subtherapeutic, and highly variable when compared to mean levels measured in the general population. Multiple drug levels were measured in these patients, as the clinicians were aware of the possible impact of bariatric surgery. The drug levels were used as additional input for clinical decision-making. All four patients required TKI switches and/or dose modifications to achieve an effective and tolerable treatment. Eventually, adequate clinical and molecular remissions were achieved in all cases. In summary, TKI concentrations of patients undergoing bariatric surgery may be subtherapeutic. Moreover, there is substantial interindividual and intraindividual variation, which may be explained by the complex interference of bariatric surgery and associated weight loss. For clinical practice, therapeutic drug monitoring is advised in patients with a history of bariatric surgery in case of suboptimal response or loss of response.

A Dutch Survey on Medication Adjustments after Metabolic and Bariatric Surgery: Experiences of Bariatric Surgeons, Internists, Pharmacists, and General Practitioners.

BACKGROUND: As metabolic and bariatric surgery (MBS) can alter the pharmacokinetics of drugs, post-bariatric surgery patients may require medication adjustments and monitoring. To improve pharmacotherapy in these patients, we aimed to understand the beliefs, attitudes, knowledge, and concerns of healthcare professionals who treat these patients. METHODS: A survey by means of an online questionnaire was divided into six sections. It was sent to bariatric surgeons, internists, pharmacists, and general practitioners in the Netherlands. RESULTS: Out of 229 returned surveys, 222 were included. Virtually all respondents (98%) expected MBS to influence the effect of medication. Both reduced efficacy (23%) and more adverse events or medication-related complications (21%) were recognized. Two-thirds of the respondents felt competent to prescribe or to provide advice regarding medication in post-bariatric surgery patients. Most of the respondents (95%) believed that other healthcare professionals should be aware of the contraindication "bariatric surgery". Of the respondents, 37% indicated that they were not aware of the medication advice incorporated in the electronic health record systems. Almost half of the respondents (48%) indicated that they documented changes in drug effects. Most respondents answered that these ought to be registered in the pharmacovigilance database or national registry. CONCLUSIONS: The majority of prescribers and pharmacists believe that patients will receive better pharmacotherapy if healthcare professionals take MBS into account. However, not all prescribers think they are competent to act adequately. To improve this, information on changed drug effects after MBS should be more widely shared among healthcare professionals via resources that are easily accessible.