The kinetics of integrilin limited by obesity: a multicenter randomized pharmacokinetic and pharmacodynamic clinical trial.

BACKGROUND: KILO tested 2 novel weight-based eptifibatide dosing strategies compared with standard dosing in obese patients undergoing elective percutaneous coronary intervention (PCI). Eptifibatide dosing is weight adjusted for patients up to 121 kg. Patients above this weight receive the same maximal dose, although it is unknown if this provides adequate eptifibatide concentration or platelet inhibition. METHODS: Sixty-seven patients weighing ≥125 kg undergoing elective PCI were randomized to 1 of 3 eptifibatide dosing regimens: standard dosing using a weight of 121 kg, actual body weight (ABW)-based dosing with no upper limit, or ideal body weight (IBW)-based dosing. Boluses of 180 µg/kg were given 10 minutes apart, followed by a 2.0 µg/kg per minute infusion. Plasma eptifibatide concentrations were drawn at 12 to 18 hours after initiating the infusion. Platelet aggregation was assessed at baseline and 10 minutes after the second bolus. RESULTS: Sixty-seven patients were randomized to standard (n = 22), ABW (n = 23), or IBW (n = 22) dosing. The median (25th, 75th) steady-state plasma eptifibatide concentrations were 1,740 ng/mL (1,350, 2,350), 1,780 ng/mL (1,510, 2,350), and 1,055 ng/mL (738, 1,405), respectively (P < .001). Ten-minute median (25th, 75th) platelet aggregation units were 7 (0, 21), 2 (0, 8), and 14 (8, 20), respectively (P = .001). CONCLUSIONS: Actual body weight eptifibatide dosing leads to higher plasma concentrations and greater platelet inhibition than standard or IBW dosing in obese patients undergoing PCI. Current recommendations for eptifibatide dosing may be inadequate in patients >121 kg. Further study is warranted to define the optimal dosing of eptifibatide and other medications in obese patients.

Direct thrombin inhibitors are not equally effective in vivo against arterial thrombosis: in vivo evaluation of DuP714 and argatroban in a porcine angioplasty model and comparison to r-hirudin.

BACKGROUND: Qualitative differences in antithrombotic efficacy between thrombin inhibitors may be explained by the affinity for which they bind thrombin. This affinity is inversely proportional to the inhibitory constant for the agent (Ki). Thrombin inhibitors, DuP714 (Ki=10(-11)) and argatroban (Ki=10(-8)), were compared to our previous studies with r-hirudin (Ki=10(-13)). METHODS AND RESULTS: Prior to balloon angioplasty, thirty pigs randomly received DuP714 (0.1 mg/kg bolus and 0.6 mg/kg/h infusion; n=8), argatroban (0.2 mg/kg/min. continuous infusion; n=9), or saline (n=17). Injured arterial segments were measured for (111)In-platelet and 125I-fibrin(ogen) deposition and the incidence of macroscopic thrombus. In DuP714-treated animals, platelet and fibrin(ogen) deposition were significantly lower than controls in both carotid (10+/-2 vs. 62+/-18 and 20+/-4 vs. 74+/-6) and coronary (10+/-4 vs. 160+/-63 and 17+/-3 vs. 86+/-22) arteries (p<0.005). In contrast, platelet and fibrin(ogen) deposition were similar when comparing argatroban to saline in carotid (41+/-20 vs. 40+/-9 and 71+/-5 vs. 49+/-7) and coronary (92+/-33 vs. 151+/-45 and 114+/-37 vs. 89+/-38) arteries (p=0.82 and 0.38, respectively). Compared to argatroban, fibrin(ogen) (p<0.001) and coronary platelet deposition (p<0.05) were significantly reduced in animals treated with DuP714 with no significant difference in carotid platelet deposition (p=0.10). Neither inhibitor prevented macroscopic thrombosis. In previous studies with r-hirudin in this model, platelet deposition was limited to a monolayer with complete inhibition of macroscopic thrombus. CONCLUSIONS: Direct thrombin inhibitors do not equally prevent arterial thrombosis. Qualitative differences may be explained in part by the affinity for which they bind thrombin.