Repeated infusions of VWF/FVIII concentrate: impact of VWF:FVIII ratio on FVIII trough and peak levels in a rabbit model.

The ratio of von Willebrand factor (VWF) to FVIII differs among available VWF/FVIII concentrates. Repeated infusions of concentrates with a low VWF:FVIII ratio may expose patients with von Willebrand disease to supranormal FVIII levels. The aim of this study was to determine the effects of repeated infusions with two VWF/FVIII concentrates differing in VWF:FVIII ratio on attained FVIII trough and peak levels as well as other pharmacokinetic parameters. Rabbits were randomized to receive multiple 150 IU kg⁻¹ VWF:RCo infusions at 4 h intervals with VWF/FVIII concentrates of a high (Haemate® P/Humate-P®) or low (Wilate®) VWF:FVIII ratio. Trough plasma FVIII and VWF levels were measured after each infusion. Pharmacokinetic analysis was performed using samples collected frequently after infusion. Mean FVIII trough level after the first Wilate infusion was 50.6 IU dL⁻¹ with a 95% confidence interval (CI) of 43.1-58.2 IU dL⁻¹, compared with 31.8 IU dL⁻¹ (CI, 24.4-39.1 IU dL⁻¹) for Haemate P (P<0.001). Trough levels progressively increased over the 24 h treatment period in both groups. After the final infusion, mean trough FVIII remained significantly higher (P = 0.002) in recipients of Wilate. Mean peak FVIII concentration after infusion was 67% higher in the Wilate group (167 vs. 100 IU dL⁻¹ , respectively; P = 0.002). Mean cumulative exposure to FVIII, as measured by area under the curve, was 84% greater in Wilate-treated animals. Half-life did not differ between the two concentrates. Animal model data suggest that exposure to elevated FVIII levels can be reduced through use of VWF/FVIII concentrates with higher VWF:FVIII ratios.

Prothrombin complex concentrate mitigates diffuse bleeding after cardiopulmonary bypass in a porcine model.

BACKGROUND: Extracorporeal circuit priming and intravascular volume expansion during cardiopulmonary bypass (CPB) may lead to dilutional coagulopathy and excessive diffuse postoperative bleeding. Prothrombin complex concentrate (PCC) containing clotting factors II (FII), VII (FVII), IX (FIX), and X (FX) could be of potential value in correcting dilutional coagulopathy and reducing blood loss. METHODS: Anaesthetized pigs underwent CPB with hypothermia for 2 h at 25°C followed by 1 h of normothermia. Approximately 1 h after CPB, animals randomly received either isotonic saline 1 ml kg⁻¹ or PCC 30 IU kg⁻¹ in a volume of 1 ml kg⁻¹. Diffuse coagulopathic bleeding was assessed as suture hole blood loss from a Gore-Tex patch placed over a full-thickness incision in the left carotid artery. RESULTS: After CPB, levels of FII, FVII, FIX, and FX declined from baseline by 32% to 48%, and PCC fully or partially reversed those deficits. Median suture hole blood loss after administration of saline placebo was 74 ml. PCC reduced suture hole bleeding by a median of 54 ml with a 95% confidence interval of 6-112 ml (P=0.026) compared with saline. PCC, but not saline, normalized skin bleeding time. Peak thrombin generation markedly decreased after CPB, but then returned in PCC-treated animals to a level higher than baseline by 28.7 nM (14.5-41.1 nM; P=0.031). CONCLUSIONS: PCC was effective in correcting dilutional coagulopathy and reducing diffuse bleeding in an in vivo large-animal CPB model. Further research is warranted on PCC as a haemostatic agent in CPB.

Prothrombin complex concentrate vs fresh frozen plasma for reversal of dilutional coagulopathy in a porcine trauma model.

BACKGROUND: Fluid resuscitation following traumatic injury causes haemodilution and can contribute to coagulopathy. Coagulation factor replacement may be necessary to prevent bleeding complications of dilutional coagulopathy. Compared with fresh frozen plasma (FFP), prothrombin complex concentrate (PCC) may potentially offer a more rapid and effective means of normalizing coagulation factor levels. METHODS: In anaesthetized mildly hypothermic pigs, 65-70% of total blood volume was substituted in phases with hydroxyethyl starch and red cells. Animals were then treated with 15 ml kg(-1) isotonic saline placebo, 25 IU kg(-1) PCC, or 15 ml kg(-1) FFP. Immediately thereafter, either a standardized femur or spleen injury was inflicted, and coagulation function, including thrombin generation, and bleeding were assessed. An additional group received high-dose FFP (40 ml kg(-1)) before femur injury. RESULTS: Haemodilution markedly prolonged prothrombin time and reduced peak thrombin generation. PCC, but not FFP, fully reversed those effects. Compared with 15 ml kg(-1) FFP, PCC shortened the time to haemostasis after either bone (P=0.001) or spleen (P=0.028) trauma and reduced the volume of blood lost (P<0.001 and P=0.015, respectively). Subsequent to bone injury, PCC also accelerated haemostasis (P=0.003) and diminished blood loss (P=0.006) vs 40 ml kg(-1) FFP. CONCLUSIONS: PCC was effective in correcting dilutional coagulopathy and controlling bleeding in an in vivo large-animal trauma model. In light of its suitability for more rapid administration than FFP, PCC merits further investigation as a therapy for dilutional coagulopathy in trauma and surgery.

Prevention of gynaecological adhesions using haemostatic fleece in a rabbit model.

This pre-clinical study was performed to investigate the ability of the haemostatic fleece TachoComb to prevent adhesion formation following uterine surgery. Thirty rabbits were randomized to receive TachoComb or no intervention following incision to the right uterine horn. After 14 days, the animals were killed and examined for the presence of adhesion. The lengths of any adhesions were measured and the severity was recorded as a score (0, no adhesion; 1, adhesion easy to lyse; 2, adhesion lysed with traction; 3, adhesion separated by sharp dissection). The incidence of adhesions was 100% in the control group compared with 33% in the TachoComb-treated animals. The mean adhesion score was significantly lower (0.7 versus 2.2) and the mean adhesion length category was significantly shorter (0.4 versus 2.0) with TachoComb than in the control group. This study indicates that TachoComb is a well-tolerated and effective means of preventing adhesion following gynaecological surgery.

Four-factor prothrombin complex concentrate reverses apixaban-associated bleeding in a rabbit model of acute hemorrhage.

BACKGROUND: Apixaban is a direct factor Xa inhibitor approved for the treatment and prevention of thromboembolic disease. There is a lack of data regarding its reversal in cases of acute bleeding or prior to emergency surgery that needs addressing. OBJECTIVES: This study assessed whether a four-factor prothrombin complex concentrate (4F-PCC; Beriplex(®) /Kcentra(®) , CSL Behring) can effectively reverse apixaban-associated bleeding in an in vivo rabbit model and evaluated the correlations between in vivo hemostasis and in vitro coagulation parameters. METHODS: For dose-finding purposes, anesthetized rabbits were treated with a single intravenous dose of apixaban (800-1600 µg kg(-1) ) and, following a standardized kidney incision, volume of blood loss and time to hemostasis were measured. In a subsequent study phase, anesthetized rabbits were treated with apixaban 1200 µg kg(-1) followed by 4F-PCC (6.25-100 IU kg(-1) ), and the effects on the same bleeding parameters were assessed. In parallel, coagulation parameters were monitored. RESULTS: Dose-dependent increases in time to hemostasis and total blood loss were observed post apixaban administration. Preincision treatment with 4F-PCC resulted in a statistically significant reversal in bleeding time (all doses) and volume (doses ≥ 12.5 IU kg(-1) ). Of the coagulation parameters measured, thrombin generation initiated using the RD reagent (phospholipids only) was the most sensitive to in vivo measures of 4F-PCC's hemostatic efficacy, although some correlations were also observed for prothrombin time and whole blood clotting time. CONCLUSIONS: In this rabbit model of acute hemorrhage, 4F-PCC showed potential for reversing the bleeding effects of apixaban. Clinical data in apixaban-treated patients are needed to confirm these results.

Combination of antibiotic treatment with the thrombin inhibitor recombinant hirudin for the therapy of experimental Klebsiella pneumoniae sepsis.

Rats which were infected with the gramnegative pathogen Klebsiella pneumoniae develop disseminated intravascular coagulation (DIC), multi-organ failure (MOF) and finally die in a septic shock. We investigated the therapeutic effect of antibiotic (tobramycin) treatment combined with the infusion of the highly specific thrombin inhibitor rec. hirudin. Although administration of 2 mg/kg tobramycin alone leads to a decrease of the bacterial burden, DIC could not be prevented. Infusion of rec. hirudin (0.25 mg/kg x h) for 4 h (start of treatment 1 h post infection), in addition to a bolus administration of tobramycin, led to an amelioration of DIC parameters as fibrinogen, thrombin-antithrombin complex (TAT) and platelets. Serum transaminase levels (GOT, GPT) as a marker of MOF were significantly improved by rec. hirudin, the T50 value increased from 17 h in the tobramycin group to 42 h in the tobramycin+rec. hirudin group, mortality rates were 90% or 60%, respectively. Combination of heparin (100 U/kg x h) and tobramycin was not effective on survival.

Reduction of mortality with antithrombin III in septicemic rats: a study of Klebsiella pneumoniae induced sepsis.

Experimental gram-negative sepsis was induced in the rat by Klebsiella pneumoniae. Although bacteria are susceptible to the treatment with the antibiotic Tobramycin, DIC could not be prevented. DIC was manifested by a leuko- and thrombocytopenia, decreases in fibrinogen and AT III and an increase of the aPTT. In this model the therapeutic treatment with human AT III was evaluated. To determine the optimal concentration of AT III a prestudy in a LPS induced DIC in the rat was performed. It was shown that a bolus i.v. injection of 500 U/kg improved survival and DIC, and was thus chosen for the Klebsiella sepsis model. The infectious load was adjusted to yield a mortality rate of 90-100% in the untreated Klebsiella group and a reduction to about 40-50% of the mortality rate by Tobramycin. It was found that AT III reduced mortality in the Klebsiella induced sepsis not only when given prophylactically but was effective even when administrated in a late stage of the DIC, i.e. 3 or 5 h post infection.

Development of an anti-bleeding agent for recombinant hirudin induced skin bleeding in the pig.

Recombinant hirudin (rH) is a highly specific thrombin inhibitor which is under clinical investigation for various thrombotic disorders. However, one of its potential risks during clinical use might be hemorrhage, especially when combined with other agents interfering with the coagulation system like antiplatelet or fibrinolytic agents. In this experimental study we investigated whether Haemate, a von Willebrand Factor (vWF) and factor VIII containing product, could correct rH/aspirin induced bleeding in an experimental pig study. Skin bleeding time was evaluated in three open, placebo-controlled, randomized studies following comparable designs. A total of 62 animals were given a short-term infusion of aspirin (20 mg/kg) followed by a three-hour infusion of a high or low dose (0.3 or 0.5 mg/kg/h) of rH. At cessation of rH infusion, animals were allocated to treatment with either Haemate (30 FVIII U/kg) or the recombinant factor VIII, Helixate, which is devoid of vWF. The skin bleeding time (SBT, given as times of baseline) as measured four hours after the start of the rH infusion was defined as the prospective endpoint. In study 1 (low dose rH + Haemate) 4 h SBT was 2.18 (placebo) and 1.61 (Haemate, p = 0.0111). In study No. 2 (high dose rH + Haemate) SBT was 2.58 in placebo and 1.73 in Haemate (p = 0.0001). No significant difference between placebo and treatment were detected in study No. 3 (low dose rH + Helixate). Haemate but not Helixate significantly decreased bleeding time as compared to placebo at termination of the study (7 hours) which was defined as the secondary endpoint. No effect on either aPTT nor rH plasma levels were observed with any of the study drugs. It was concluded that Haemate decreases excess bleeding induced by rH/aspirin treatment without altering rH's anticoagulant effect.

First-pass elimination of a peptidomimetic thrombin inhibitor is due to carrier-mediated uptake by the liver. Interaction with bile acid transport systems.

CRC 220 (4-methoxy-2, 3, 6-trimethylphenylsulfonyl-L-aspartyl-D-4-amidinophenylalanyl -piperidide) is a competitive peptide-based trombin inhibitor with high affinity to human alpha-thrombin (Ki 2.5 nM). The amphiphilic compound exhibits virtually no systemic bioavailability despite proteolytic stability and proven enteral absorption. After intravenous application (V. jejunalis) in rats CRC 220 is almost completely excreted into bile. Simultaneous administration of bile acids considerably decreases this first-pass elimination. CRC 220 is extensively taken up in isolated rat hepatocytes by a saturable carrier-mediated transport with Km 23.7 microM and Vmax 775 pmol x mg-1 x min-1. A large part of this transport is energy-dependent. At temperatures above 20 degrees C, the uptake is accelerated exponentially. The activation energy amounts to 82 kj/mol. A minor portion of CRC 220 uptake occurs by physical diffusion with a permeability coefficient of 7.83 x 10(-7) cm/sec at 12 degrees C. Sodium ions energize CRC 220 uptake. Replacement of sodium by choline or lithium decreases the transport rate of 23-40%. In addition, a negative membrane potential facilitates the uptake. CRC 220 transport is only observed in hepatocytes: it is absent in BHK, FAO, HepG2, HPCT 1E3, and HPCT 1E3-TC cells. In the presence of 4-amidinophenylalanine derivatives, CRC 220 uptake is considerably decreased. Inhibition also occurs with bile acids and bromosulfophthalein, but less with bumetanide. Because CRC 220 inhibits bile acid uptake into hepatocytes and vice versa, the results suggest that the first-pass elimination of this amphiphilic thrombin inhibitor is due to an active carrier-mediated transport process in the basolateral plasma membrane of rat hepatocytes, and that this transport occurs via a bile acid transport system.

Pharmacological characterization of a new 4-amidinophenyl-alanine thrombin-inhibitor (CRC 220).

The new thrombin inhibitor CRC 220 was characterized in vivo for its antithrombotic effects. CRC 220 led to a dose-dependent prolongation of clotting parameters as determined in rats, rabbits, dogs, sheeps, pigs and monkeys. We evaluated the efficacy of CRC 220 to prevent thrombus formation in arteries and in the microcirculation in different animal models. In a rabbit model of tissue factor-induced coagulation activation, infusion of 0.5 mg/kg x h CRC 220 (3 hours) led to a significant prevention of fibrinogen decrease. In a rat model of lethal LPS-induced DIC CRC 220 significantly prevented the mortality rate after a 4h-infusion of 0.75 mg/kg x h. Thrombin-induced platelet aggregation in rat lungs could be prevented by the i.v. bolus injection of CRC 220. A dose of 0.3 mg/kg leads to a reduction of more than 80% of platelet deposition in the lung, significant inhibition was still observed 90 minutes after CRC 220 administration; at this time the inhibitor had already been cleared from plasma. Arterial thrombosis was induced in rabbits by squeezing and stenosis of the A. carotis. The i.v. bolus administration of CRC 220 dose-dependently prevented thrombus formation, an ED50 of 0.03 mg/kg was calculated. This dose was associated with only a minor prolongation of aPTT.

The potentiation of human C1-inhibitor by dextran sulphate is transient in vivo: studies in a rat model.

C1-inhibitor (C1-Inh) is an important regulator of inflammatory reactions because it is a potent inhibitor of the contact and complement system. C1-Inh application in inflammatory disease is, however, restricted because of the high doses required. The glycosaminoglycan-like molecule dextran sulphate (DXS) enhances C1-Inh function in vitro. Hence, we investigated whether co-administration with dextran sulphate reduces the amount of C1-Inh required, through enhancement in vivo. C1-Inh potentiation was measured in a newly developed C1s-inactivation assay that is based on activation of C4 by purified C1s. Activated C4 in rat plasma was quantified with a newly developed ELISA. Human C1-Inh (2.5 microM) inhibited C1s in rat plasma 55-fold faster in the presence of dextran sulphate (15 kDa, 5 microM). To study the stability of the complex in vivo, rats were given a mixture of C1-Inh (10 mg/kg) and dextran sulphate (3 mg/kg). C1-Inh activity during 5 h was analyzed ex vivo with the C1s inactivation assay. The noncovalent C1-Inh-dextran sulphate complex resulted in a transient enhancement of the inhibitory capacity of C1-Inh, lasting for 60-90 min. Dextran sulphate did not affect plasma clearance of C1-Inh. We conclude that the enhanced inhibitory capacity of C1-Inh complexed to dextran sulphate is transient in vivo. Hence, co-administration of these compounds seems a feasible approach to achieve short-term inhibition of complement in vivo.

Treatment of porcine sepsis with high-dose antithrombin III reduces tissue edema and effusion but does not increase risk for bleeding.

We evaluated the effectiveness of antithrombin III (AT III) infusions designed to achieve supraphysiologic plasma levels of this serine protease inhibitor in preventing vascular permeability and disseminated intravascular coagulation in a pig model of sepsis. In addition, we determined whether high AT III doses were associated with increased bleeding risk. Sepsis was induced in 18 pigs by injection of lipopolysaccharide (LPS) (0.25 microg/kg per h for 3 h). At 90 min after the start of LPS infusion, pigs were randomized (n = 6 per group) to receive either human serum albumin as a placebo, AT III 120/5 (120 U/kg, 30-min bolus + 5 U/kg per h for 240 min), or AT III 250/10 (250 U/kg + 10 U/kg per h). Three additional animals served as negative controls (no LPS, no AT III). Treatment with AT III significantly reduced the amount of effluents in body cavities and fibrin monomers. AT III did not significantly increase bleeding risk as determined by organ hemorrhage. An additional assessment of AT III's bleeding risk [skin bleeding time (SBT)] was carried out in 35 nonseptic pigs treated with either AT III alone (120/5 or 250/10) or in the combination with heparin. Heparin administration alone produced a dose-dependent increase in SBT, but AT III alone did not. Addition of AT III 120/5 to heparin did not induce a further increase in bleeding time over heparin alone. These results indicate that administration of AT III in doses designed to achieve very high plasma concentrations significantly ameliorates symptoms of sepsis-induced vascular leakage and disseminated intravascular coagulation without increasing bleeding risk.

Chemotherapeutics: a questionable or a promising project.

While repository adjuvants are already established drugs for antigen specific immunomodulation, no unspecific active immunomodulator has successfully passed clinical trials in tumor patients in Western countries yet. As this is in striking contrast to the effects seen with unspecific immunomodulators in experimental immunological and tumor test systems, the value of those screening models to predict clinical success may be asked for. To improve the success rate, it is recommended to test compounds for their immunomodulatory effects as broad as possible in ex vivo and in vivo test systems. Subsequently, the prophylactic as well as therapeutic potency of selected immunomodulating drugs should be evaluated in various models of aptitude, such as chronic infection, autoimmune diseases and chronic inflammatory reactions. Those diseases are at least to a certain extent influenced by the immune system, in contrast to the uncertainty in case of tumor diseases. In a battery of chronic infection models we could find that different chemoimmunotherapeutics with very similar immunopharmacological activity behaved quite different. Most compounds were ineffective, a part enhanced chronic diseases and only in a few cases a therapeutic effect could be shown. On the other hand, effectivity in protection against the pathogenicity of subsequently applied, selected microorganisms does not predict the therapeutic potency for the same pathogen. Altogether the data show that activation of cells of the immune system by an immunostimulating drug does not predict its therapeutic potency. Moreover, activation of immune cells may also impair the immune resistance.

Cefodizime, an aminothiazolyl cephalosporin. IV. Influence on the immune system.

Studies concerning the activity of cefodizime (HR 221), on certain aspects of the immune response, were conducted. It was found that lymphocytes from Balb/c mice treated with 3 and 30 mg/kg/day of cefodizime display increased responsiveness to B-cell mitogens and specific antigens. Also, the amount of antigen specific antibody producing plaque forming cells was increased in these mice and was accompanied by a rise in the specific IgG haemagglutinin titer. These effects were not observed in lymphocytes obtained from NMRI mice that had been treated with cefodizime. Peritoneal macrophages from NMRI mice, treated with cefodizime prior to harvesting of the cells, contained increased levels of lysosomal enzymes, developed enhanced chemiluminescent reaction to stimuli and showed elevated pinocytosis rates. Furthermore, NMRI mice treated with cefodizime during the immunization, developed enhanced DTH-reaction, when challenged with the antigen (SRBC). The prophylactic treatment of Balb/c mice with cefodizime (2 X 30 mg/kg/day ip for 4 days) significantly prolonged the mean survival time of the animals after intravenous infection with Candida albicans 200/175 (16.7 days as against 3.5 days in the case of the controls). This stimulatory effect of cefodizime on the host defence system was not observed for NMRI mice. Treatment with latamoxef or cefoperazone under the same experimental conditions did not reduce the susceptibility of mice to C. albicans. The protective activity of cefodizime against C. albicans in Balb/c mice, may be due to the immuno-stimulatory activity of this agent.

Pharmacological characteristics of a novel, recombinant fusion protein linking coagulation factor VIIa with albumin (rVIIa-FP).

BACKGROUND: Recombinant factor VIIa (rFVIIa) is approved for use in controlling bleeding episodes in people with hemophilia who have developed inhibitors to replacement therapy. Due to its short half-life (t½), frequent injections are required, limiting its use as a prophylactic treatment. A novel, recombinant fusion protein linking coagulation factor VIIa with albumin (rVIIa-FP) has been developed to extend the t(½) of rFVIIa. OBJECTIVES: The aim of our studies was to investigate the pharmacokinetic/pharmacodynamic characteristics of rVIIa-FP in preclinical animal species. METHODS: Pharmacokinetic (PK) parameters were derived after single intravenous dosing in hemophilia A mice, rats, rabbits and monkeys. PK analysis was based on human FVII plasma levels determined by measuring FVII antigen levels by ELISA in mice and rats, and FVIIa activity using STACLOT® VIIa-rTF in rabbits and monkeys. Induction of thrombin generation was investigated in mice, while hemostatic activity was assessed by thrombus formation in rabbits. RESULTS: Compared with rFVIIa, rVIIa-FP displayed a prolonged t(½), enhanced in vivo recovery and reduced clearance in all species investigated. In mice, 16 h after treatment with rVIIa-FP, thrombin levels were quantifiable, indicating prolonged efficacy, whereas values had approached baseline at this time after treatment with rFVIIa. After 12 h, hemostatic efficacy was negligible in rFVIIa-treated rabbits, but sustained in animals receiving rVIIa-FP. CONCLUSIONS: These studies indicate that the longer t(½) of rVIIa-FP compared with rFVIIa translates into extended activity. These findings suggest that rVIIa-FP has the potential to be administered less frequently than rFVIIa-containing concentrates in clinical use.

Improved kinetics of rIX-FP, a recombinant fusion protein linking factor IX with albumin, in cynomolgus monkeys and hemophilia B dogs.

BACKGROUND: Prophylaxis of hemophilia B, at present, requires multiple infusions of human factor (F)IX concentrates per week. A FIX molecule with a prolonged half-life has the potential to greatly improve the convenience of, and adherence to, prophylaxis. OBJECTIVES: The aim of our studies was to investigate the pharmacokinetic (PK) and pharmacodynamic (PD) profile of a recombinant fusion protein linking coagulation FIX with albumin (rIX-FP). METHODS: Cynomolgus monkeys and hemophilia B dogs received single intravenous doses of rIX-FP (50-500 IU kg(-1)). rIX-FP plasma levels were determined by an activity-based assay (dogs only) and anti-FIX ELISA methods. Additionally, activated partial thromboplastin time (APTT) was determined in hemophilia B dogs. Data were compared with a direct study comparator (recombinant FIX [rFIX]) or previously published data. RESULTS: The terminal half-life of rIX-FP was prolonged in both species compared with FIX reference data. In hemophilia B dogs, human FIX antigen levels remained above 0.05 IU mL(-1) more than three times longer after rIX-FP (7.3 days) compared with rFIX (2.3 days), whereas respective calculations based on activity levels confirmed the observed superior profile. Prolonged PDs of rIX-FP were demonstrated with APTT<60 s sustained around four times longer with rIX-FP (5.9 days) than rFIX (1.5 days). CONCLUSIONS: These studies indicate that the recombinant albumin fusion technology successfully improves the PK profile of FIX. Clinical studies will test whether the improved kinetics result in a significant half-life extension in patients with hemophilia B.

Reversal of dabigatran anticoagulation by prothrombin complex concentrate (Beriplex P/N) in a rabbit model.

BACKGROUND: One limitation of the direct thrombin inhibitor dabigatran is the lack of specific antidotes that allow acute bleeding events to be managed or urgent interventional procedures performed. Prothrombin complex concentrates (PCCs) have served as a standard treatment for the reversal of coumarin anticoagulation. OBJECTIVES: This study was designed to determine in an animal model whether a PCC (Beriplex P/N) can effectively reverse the effects of dabigatran. An additional objective was to evaluate markers of dabigatran-associated bleeding diathesis. METHODS: Anesthetized rabbits were treated with 0.4 mg kg(-1) dabigatran followed by PCC doses of 20, 35 or 50 IU kg(-1) or placebo. After a standardized kidney incision, volume of blood loss and time to hemostasis were determined. RESULTS: From an initial mean of 29 mL, blood loss progressively declined by 5.44 mL with a 95% confidence interval (CI) of 2.21-8.67 mL per 10 IU kg(-1) increment in PCC dose (P = 0.002). At a PCC dose of 50 IU kg(-1) blood loss was fully normalized. Increasing PCC doses shortened the median time to hemostasis from 20.0 to 5.7 min (P < 0.001). The rate of hemostasis was nearly trebled with each 10 IU kg(-1) increment in PCC dose (rate ratio, 2.89; CI, 1.64-5.09). CONCLUSIONS: In this animal study, PCC showed potential as an agent for reversing the effects of dabigatran. Further investigation is warranted.