Cefiderocol, a Siderophore Cephalosporin for Gram-Negative Bacterial Infections: Pharmacokinetics and Safety in Subjects With Renal Impairment

Cefiderocol, a new injectable siderophore cephalosporin antibiotic, has promising in vitro and in vivo activity against Gram-negative bacteria including multidrug-resistant Pseudomonas aeruginosa, Acinetobacter baumannii, and Klebsiella pneumoniae. Cefiderocol is mainly renally eliminated. The pharmacokinetics and safety of cefiderocol in subjects with renal impairment were assessed following a single 1000-mg intravenous 1-hour infusion of cefiderocol. Subjects with mild, moderate, or severe renal impairment and end-stage renal disease (ESRD) requiring hemodialysis were compared with demographically (age, body mass index, and sex) matched healthy subjects with normal renal function. The effect of hemodialysis on the clearance of cefiderocol was also assessed. Total drug clearance from plasma (CL) and terminal half-life (t1/2 ) correlated with renal function. Ratios (90% confidence intervals) of area under the plasma concentration-time curve from 0 to infinity (AUC) in mild, moderate, severe, and ESRD groups compared to those with normal renal function were 1.0 (0.8-1.3), 1.5 (1.2-1.9), 2.5 (2.0-3.3), and 4.1 (3.3-5.2), respectively. Maximum plasma concentration (Cmax ) was similar between renal-impairment groups and the normal-renal-function group. Approximately 60% of cefiderocol was removed by hemodialysis for 3 to 4 hours. The plasma-protein-unbound fraction was similar between various renal function groups. The incidence of adverse events did not appear to have any correlation with the degree of renal impairment. Single 1000-mg intravenous doses of cefiderocol were generally well tolerated in subjects with impaired renal function except for 1 subject who discontinued due to urticaria. In conclusion, renal impairment impacted AUC, CL, and t1/2 without affecting Cmax . Cefiderocol was significantly removed by intermittent hemodialysis.

Bile salt inhibition of motility in the isolated perfused rabbit terminal ileum

The effects of bile on small bowel motility were studied in isolated, perfused rabbit terminal ileum. It was proposed that bile delivery into the distal ileum would inhibit ileal motor activity, by peptide YY (PYY) release and therefore the effect of luminal bile on motor activity was examined and PYY release measured. Luminal bile and taurocheodeoxycholic acid (10 mmol) inhibited ileal motor activity. Arterial infusion of venous effluents from a bile inhibited ileum suppressed motor activity in a second isolated ileum. This shows the presence of a humoral inhibitor of ileal motor activity. Luminal bile increased venous PYY concentrations (42.5 (8.5) to 502 (46.2) pmol/l; p < 0.01) and increased bile salt values (1.7 (0.36) to 88.6 (5.6) 10 mumol/l/l; p < 0.005). Arterial infusion of taurocheodeoxycholic acid at concentrations found in the venous effluent (100 mumol/l/l) suppressed motility (p < 0.001) but infusion of PYY at concentrations in the venous effluent (500.0 pmol/l) failed to inhibit motility. Furthermore, PYY antagonist, PYX 1, failed to reverse the bile induced inhibition of motility. Luminal bile salts inhibit terminal ileal motility and this is independent of PYY release. By slowing motility, bile salts may participate in their own absorption by the 'ileal pump' and in the 'ileal brake' mechanism.

Sudden development of intraoperative left ventricular outflow obstruction: differential and mechanism. An intraoperative two-dimensional echocardiographic study

Systolic anterior motion (SAM) of the mitral valve, once considered to be pathognomonic of hypertrophic cardiomyopathy, has been reported in the absence of asymmetric septal hypertrophy. Of the 1,000 open heart operations performed with intraoperative two-dimensional epicardial echocardiography monitoring, four patients developed intraoperative dynamic left ventricular outflow obstruction associated with systolic anterior motion of the mitral valve that was not present preoperatively: three cases of mitral valve annuloplasty with Carpentier ring insertion and one of coronary artery bypass grafting. Though no patient had asymmetric septal hypertrophy or echocardiographic evidence of outflow obstruction by either preoperative cardiac catheterization or echocardiography, intraoperative two-dimensional epicardial echocardiography revealed SAM, and hyperdynamic left ventricles with three of these patients having documented left ventricular outflow tract gradients causing hemodynamic compromise. (Case 4 was hemodynamically stable following mitral valve repair, but had SAM and significant residual mitral regurgitation [MR] requiring reinstitution of cardiopulmonary bypass and re-repair). Measurement of mitral annular dimension demonstrated a normal decrease in size from diastole to systole in control operative subjects but not in the patients who developed outflow obstruction. The pathophysiology, treatment, and role of intraoperative echocardiography of dynamic left ventricular outflow tract obstruction are discussed.