Stomach pH before vs. after different bariatric surgery procedures: Clinical implications for drug delivery

Abstract

Stomach pH may vary following bariatric surgery, with implications for drug delivery/bioavailability. Yet, this parameter has not been studied. In this work, gastric content was aspirated from patients before, immediately after, and the day after different bariatric procedures, and pH was immediately measured. Compared to pre-surgery (1.8), pH was increased one day after one-anastomosis gastric bypass (OAGB) and sleeve gastrectomy (LSG) by 3-4 pH units; pH immediately after these procedures was in between the other 2 time points. Post-OAGB pH was significantly higher than post-LSG (6.4 and 4.9, respectively). Prior adjustable gastric band did not significantly alter baseline pH. We then performed drug dissolution studies of the antiplatelet drugs dipyridamole and aspirin, mimicking pre-surgery, post-LSG and post-OAGB conditions, implementing our pH results and other relevant physiological parameters. Dipyridamole, a weak base, completely dissolved (100% of dose) under pre-surgery conditions, while dissolution was hampered under post-LSG (5%) and post-OAGB (0.25%) conditions, due to solubility limit. Aspirin was not released from enteric-coated tablet under pre-surgery or post-LSG gastric conditions, however, >75% dissolved within 15 min under post-OAGB gastric conditions, indicating potential failure of enteric coating, depending on the bariatric procedure. In conclusion, special care should be taken when using pH-dependent drugs and drug products after bariatric surgery, and the use of pH-independent formulations should be preferred. Overall, this research revealed the interim gastric pH after different bariatric procedures, and potentially important effects on post-bariatric oral drug delivery and treatment.

Keywords: Adjustable gastric band; Aspirin; Dipyridamole; Drug dissolution; Enteric coating; Gastric pH; Laparoscopic sleeve gastrectomy; One anastomosis gastric bypass.