In vitro to in vivo extrapolation and physiologically based modeling of cytochrome P450 mediated metabolism in beagle dog gut wall and liver.

The beagle dog is a widely used in vivo model to guide clinical formulation development and to explore the potential for food effects. However, the results in dogs are often not directly translatable to humans. Consequently, a physiologically based modeling strategy has been proposed, using the dog as a validation step to verify model assumptions before making predictions in humans. One current weakness in this strategy is the lack of validated tools to incorporate gut wall metabolism into the dog model. In this study, in vitro to in vivo extrapolation factors for CYP2B11 and CYP3A12 mediated metabolism were established based on tissue enzyme abundance data reported earlier. Thereafter, physiologically based modeling of intestinal absorption in beagle dog was conducted in GastroPlus using V(max) and K(m) determined in recombinant enzymes as inputs for metabolic turnover. The predicted fraction of absorbed dose escaping the gut wall metabolism (F(g)) of all five reference compounds studied (domperidone, felodipine, nitrendipine, quinidine, and sildenafil) were within a two-fold range of the value estimated from in vivo data at single dose levels. However, further in vivo studies and analysis of the dose-dependent pharmacokinetics of felodipine and nitrendipine showed that more work is required for robust forecasting of nonlinearities. In conclusion, this study demonstrates an approach for prediction of the gut wall extraction of CYP substrates in the beagle dog, thus enhancing the value of dog studies as a component in a strategy for the prediction of human pharmacokinetics.

Assessment of steroid use as a key performance indicator in inflammatory bowel disease-analysis of data from 2385 UK patients.

BACKGROUND: Patients with IBD are at risk of excess corticosteroids. AIMS: To assess steroid excess in a large IBD cohort and test associations with quality improvement and prescribing. METHODS: Steroid exposure was recorded for outpatients attending 19 centres and associated factors analysed. Measures taken to avoid excess were assessed. RESULTS: Of 2385 patients, 28% received steroids in the preceding 12 months. 14.8% had steroid excess or dependency. Steroid use was significantly lower at 'intervention centres' which participated in a quality improvement programme (exposure: 23.8% vs 31.0%, P < .001; excess 11.5% vs 17.1%, P < .001). At intervention centres, steroid use fell from 2015 to 2017 (steroid exposure 30.0%-23.8%, P = .003; steroid excess 13.8%-11.5%, P = .17). Steroid excess was judged avoidable in 50.7%. Factors independently associated with reduced steroid excess in Crohn's disease included maintenance with anti-TNF agents (OR 0.61 [95% CI 0.24-0.95]), treatment in a centre with a multi-disciplinary team (OR 0.54 [95% CI 0.20-0.86]) and treatment at an intervention centre (OR 0.72 [95% CI 0.46-0.97]). Treatment with 5-ASA in CD was associated with higher rates of steroid excess (OR 1.72 [95% CI 1.24-2.09]). In ulcerative colitis (UC), thiopurine monotherapy was associated with steroid excess (OR 1.97 [95% CI 1.19-3.01]) and treatment at an intervention centre with less steroid excess (OR 0.72 [95% CI 0.45-0.95]). CONCLUSIONS: This study validates steroid assessment as a meaningful quality measure and provides a benchmark for this performance indicator in a large cohort. A programme of quality improvement was associated with lower steroid use.