Pharmacological properties : תכונות פרמקולוגיות

Pharmacodynamic Properties

12.2 Pharmacodynamics
Infusion of eptifibatide into baboons caused a dose-dependent inhibition of ex vivo platelet aggregation, with complete inhibition of aggregation achieved at infusion rates greater than 5 mcg/kg/min. In a baboon model that is refractory to aspirin and heparin, doses of eptifibatide that inhibit aggregation prevented acute thrombosis with only a modest prolongation (2- to 3-fold) of the bleeding time. Platelet aggregation in dogs was also inhibited by infusions of eptifibatide, with complete inhibition at 2 mcg/kg/min. This infusion dose completely inhibited canine coronary thrombosis induced by coronary artery injury (Folts model).
Human pharmacodynamic data were obtained in healthy subjects and in patients presenting with UA or NSTEMI and/or undergoing percutaneous coronary intervention. Studies in healthy subjects enrolled only males; patient studies enrolled approximately one-third women. In these studies, INTEGRILIN inhibited ex vivo platelet aggregation induced by adenosine diphosphate (ADP) and other agonists in a dose- and concentration-dependent manner. The effect of INTEGRILIN was observed immediately after administration of a 180-mcg/kg intravenous bolus. Table 4 shows the effects of dosing regimens of INTEGRILIN used in the IMPACT II and PURSUIT studies on ex vivo platelet aggregation induced by 20 µM ADP in PPACK-anticoagulated platelet-rich plasma and on bleeding time. The effects of the dosing regimen used in ESPRIT on platelet aggregation have not been studied.
Table 4: Platelet Inhibition and Bleeding Time
PURSUIT
180/2*
Inhibition of platelet aggregation 15 min after bolus                                   84% 

Inhibition of platelet aggregation at steady state                         >90% 
Bleeding-time prolongation at steady state                                 <5x Inhibition of platelet aggregation 4h after infusion discontinuation       <50% 
Bleeding-time prolongation 6h after infusion discontinuation               1.4x 

* 180-mcg/kg bolus followed by a continuous infusion of 2 mcg/kg/min.

The INTEGRILIN dosing regimen used in the ESPRIT study included two 180-mcg/kg bolus doses given 10 minutes apart combined with a continuous 2-mcg/kg/min infusion.
When administered alone, INTEGRILIN has no measurable effect on PT or aPTT.
There were no important differences between men and women or between age groups in the pharmacodynamic properties of eptifibatide. Differences among ethnic groups have not been assessed.

Pharmacokinetic Properties

12.3 Pharmacokinetics
The pharmacokinetics of eptifibatide are linear and dose-proportional for bolus doses ranging from 90 to 250 mcg/kg and infusion rates from 0.5 to 3 mcg/kg/min. Plasma elimination half-life is approximately 2.5 hours.
Administration of a single 180-mcg/kg bolus combined with an infusion produces an early peak level, followed by a small decline prior to attaining steady state (within 4-6 hours). This decline can be prevented by administering a second 180- mcg/kg bolus 10 minutes after the first. The extent of eptifibatide binding to human plasma protein is about 25%.
Clearance in patients with coronary artery disease is about 55 mL/kg/h. In healthy subjects, renal clearance accounts for approximately 50% of total body clearance, with the majority of the drug excreted in the urine as eptifibatide, deaminated eptifibatide, and other, more polar metabolites. No major metabolites have been detected in human plasma.
Special Populations
Geriatric
Patients in clinical studies were older (range: 20-94 years) than those in the clinical pharmacology studies. Elderly patients with coronary artery disease demonstrated higher plasma levels and lower total body clearance of eptifibatide when given the same dose as younger patients. Limited data are available on lighter weight (<50 kg) patients over 75 years of age.
Renal Impairment
In patients with moderate to severe renal insufficiency (CrCl <50 mL/min using the Cockcroft-Gault equation), the clearance of eptifibatide is reduced by approximately 50% and steady-state plasma levels approximately doubled [see Use in Specific Populations (8.6) and Dosage and Administration (2)].
Hepatic Impairment
No studies have been conducted in patients with hepatic impairment.
Gender
Males and females have not demonstrated any clinically significant differences in the pharmacokinetics of eptifibatide.