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BackgroundHereditary angioedema (HAE) due to C1 inhibitor deficiency manifests as recurrent swelling attacks that can be disabling and sometimes fatal. Long‐term prophylaxis with twice‐weekly intravenous injections of plasma‐derived C1‐inhibitor (pdC1‐INH) has been established as an effective treatment. Subcutaneous (SC) administration of pdC1‐INH has not been studied in patients with HAE.MethodsThis open‐label, dose‐ranging, crossover study (COMPACT Phase II) was conducted in 18 patients with type I or II HAE who received two of twice‐weekly 1500, 3000, or 6000 IU SC doses of highly concentrated volume‐reduced CSL830 for 4 weeks each. The mean trough plasma levels of C1‐INH functional activity, C1‐INH and C4 antigen levels during Week 4, and overall safety and tolerability were evaluated. The primary outcome was model‐derived steady‐state trough C1‐INH functional activity.ResultsAfter SC CSL830 administration, a dose‐dependent increase in trough functional C1‐INH activity was observed. C1‐INH and C4 levels both increased. The two highest dose groups (3000 and 6000 IU) achieved constant C1‐INH activity levels above 40% values, a threshold that was assumed to provide clinical protection against angioedema attacks. Compared with intravenous injection, pdC1‐INH SC injection with CSL830 showed a lower peak‐to‐trough ratio and more consistent exposures. All doses were well tolerated. Mild‐to‐moderate local site reactions were noted with pain and swelling being the most common adverse event.ConclusionsSubcutaneous volume‐reduced CSL830 was well tolerated and led to a dose‐dependent increase in physiologically relevant functional C1‐INH plasma levels. A clinical outcome study of SC CSL830 in patients with HAE warrants further investigation.

The effects of route of administration on the stereoselective pharmacokinetics of tramadol (T) and its active metabolite (M1) were studied in rats. A single 20 mg/kg dose of racemic T was administered through intravenous, intraperitoneal, or oral route to different groups of rats, and blood and urine samples were collected. Samples were analyzed using chiral chromatography, and pharmacokinetic parameters (mean +/- SD) were estimated by noncompartmental methods. Following intravenous injection, there was no stereoselectivity in the pharmacokinetics of T. Both enantiomers showed clearance values (62.5 +/- 27.2 and 64.4 +/- 39.0 ml/min/kg for (+)- and (-)-T, respectively) that were equal or higher than the reported liver blood flow in rats. Similar to T, the area under the plasma concentration-time curves (AUCs) of M1 did not exhibit stereoselectivity after intravenous administration of the parent drug. However, the systemic availability of (+)-T was significantly (P < 0.05) higher than that of its antipode following intraperitoneal (0.527 +/- 0.240 vs. 0.373 +/- 0.189) and oral (0.307 +/- 0.136 vs. 0.159 +/- 0.115) administrations. The AUC of the M1 enantiomers, on the other hand, remained mostly nonstereoselective regardless of the route of administration. Pharmacokinetic analysis indicated that the stereoselectivity in the pharmacokinetics of oral T is due to stereoselective first pass metabolism in the liver and, possibly, in the gastrointestinal tract. The direction and extent of stereoselectivity in the pharmacokinetics of T and M1 in rats were in agreement with those previously reported in humans, suggesting that the rat may be a suitable model for enantioselective studies of T pharmacokinetics.

f Front loading is a strategy used to optimize the pharmacodynamic profile of an antibiotic through the administration of high doses early in therapy for a short duration. Our aims were to evaluate the impact of front loading of linezolid regimens on bacterial killing and suppression of resistance and on RNAIII, the effector molecule of the accessory gene regulator system (encoded by agr) in methicillin-resistant Staphylococcus aureus (MRSA). Time-killing experiments over 48 h were utilized for linezolid against four strains of MRSA: USA100, USA300, USA400, and ATCC 29213. A hollow-fiber infection model simulated traditional and front-loaded human therapeutic regimens of linezolid versus USA300 at 10 6 CFU/ml over 240 h. Over 48 h in time-kill experiments, linezolid displayed bacteriostatic activity, with reductions of >1 log 10 CFU/ml for all strains. Front-loaded regimens that were administered over 5 days, 1,200 mg every 12 h (q12h) (total, 10 doses) and 2,400 mg q12h (total, 10 doses) followed by 300 mg q12h thereafter, resulted in sustained bactericidal activity, with reductions of the area under the CFU curve of ؊6.15 and ؊6.03, respectively, reaching undetectable limits at the 10-day study endpoint. All regimens displayed a reduction in RNAIII relative expression at 24 h and 240 h compared with that of the growth control. Monte Carlo simulations predicted a <1.27؋ increase in the fractional decreases in platelets for all front-loaded regimens versus the 600 mg q12h regimen, except for the highest-dose front-loaded regimen. Front-loading strategies for linezolid are promising and may be of utility in severe MRSA infections, where early aggressive therapy is necessary.

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-Purpose.A few studies have shown that normothermic hepatic ischemia-reperfusion (IR) injury may affect the mRNA and/or protein levels of canalicular transporters P-glycoprotein (P-gp) and multidrug resistance-associated protein 2 (Mrp2). However, the effects of the injury on the functions of these canalicular transporters with respect to the biliary excretion of drugs remain largely unknown. Therefore, the purpose of this study was to investigate the effects of warm hepatic IR on the hepatobiliary disposition of rhodamine 123 (RH-123), a P-gp substrate, and its glucuronidated metabolite (RH-Glu), an Mrp2 substrate, in rats. Methods. Twenty four or 72 h following a 60-min partial ischemia or sham operation in rats, livers were isolated and perfused ex vivo with a constant concentration (~100 ng/mL) of RH-123. The concentration of RH-123 and its glucuronidated (RH-Glu) and deacylated (RH-110) metabolites were determined in the outlet perfusate, bile, and the liver tissue using HPLC, and relevant pharmacokinetic parameters were estimated. Results. Twentyfour-h IR caused a significant reduction in the hepatic extraction ratio of RH-123 (IR: 0.857 ± 0.078; Sham: 0.980 ± 0.017) and the biliary recovery of the parent drug and RH-Glu by 43% and 44%, respectively. The reductions in the biliary recovery were associated with significant reductions in the apparent biliary clearance of RH-123 and RH-Glu. Mass balance data showed that the formation of the glucuronidated or deacylated metabolite was not significantly affected by the 24-h IR injury. In contrast to the 24-h IR, the injury did not have any effect on the hepatobiliary disposition of RH-123 or its metabolites following 72 h of reperfusion. Conclusions. It is concluded that the pharmacokinetics of drugs that are subject to biliary excretion by the canalicular P-gp and Mrp2 transporters may be altered shortly after hepatic IR injury.