TY - JOUR T1 - Assessment of the Mass Balance Recovery and Metabolite Profile of Avibactam in Humans and In Vitro Drug-Drug Interaction Potential JF - Drug Metabolism and Disposition JO - Drug Metab Dispos SP - 932 LP - 942 DO - 10.1124/dmd.113.055335 VL - 42 IS - 5 AU - Karthick Vishwanathan AU - Stuart Mair AU - Anshul Gupta AU - James Atherton AU - Jacqueline Clarkson-Jones AU - Timi Edeki AU - Shampa Das Y1 - 2014/05/01 UR - http://dmd.aspetjournals.org/content/42/5/932.abstract N2 - Avibactam, a novel non-β-lactam β-lactamase inhibitor with activity against Ambler class A, class C, and some class D enzymes is being evaluated in combination with various β-lactam antibiotics to treat serious bacterial infections. The in vivo mass balance recovery and metabolite profile of [14C] avibactam (500 mg/1-h infusion) was assessed in six healthy male subjects, and a series of in vitro experiments evaluated the metabolism and drug-drug interaction potential of avibactam. In the mass balance study, measurement of plasma avibactam (using a validated liquid chromatography-tandem mass spectrometry method) and total radioactivity in plasma, whole blood, urine, and feces (using liquid scintillation counting) indicated that most of the avibactam was excreted unchanged in urine within 12 hours, with recovery complete (>97% of the administered dose) within 96 hours. Geometric mean avibactam renal clearance (158 ml/min) was greater than the product of unbound fraction of drug and glomerular filtration rate (109.5 ml/min), suggesting that active tubular secretion accounted for some renal elimination. There was no evidence of metabolism in plasma and urine, with unchanged avibactam the major component in both matrices. Avibactam demonstrated in vitro substrate potential for organic anion transporters 1 and 3 (OAT1 and OAT3) proteins expressed in human embryonic kidney 293 cells (Km > 1000 μM; >10-fold the Cmax of a therapeutic dose), which could account for the active tubular secretion observed in vivo. Avibactam uptake by OAT1 and OAT3 was inhibited by probenecid, a potent OAT1/OAT3 inhibitor. Avibactam did not interact with various other membrane transport proteins or cytochrome P450 enzymes in vitro, suggesting it has limited propensity for drug–drug interactions involving cytochrome P450 enzymes. ER -