A dose-response study in animals to evaluate the anticoagulant effect of the stage 2 unfractionated heparin USP monograph change

The US regulatory and pharmacopeia response to the global heparin contamination crisis

The contamination of the widely used lifesaving anticoagulant drug heparin in 2007 has drawn renewed attention to the challenges that are associated with the characterization, quality control and standardization of complex biological medicines from natural sources. Heparin is a linear, highly sulfated polysaccharide consisting of alternating glucosamine and uronic acid monosaccharide residues. Heparin has been used successfully as an injectable antithrombotic medicine since the 1930s, and its isolation from animal sources (primarily porcine intestine) as well as its manufacturing processes have not changed substantially since its introduction. The 2007 heparin contamination crisis resulted in several deaths in the United States and hundreds of adverse reactions worldwide, revealing the vulnerability of a complex global supply chain to sophisticated adulteration. This Perspective discusses how the US Food and Drug Administration (FDA), the United States Pharmacopeial Convention (USP) and international stakeholders collaborated to redefine quality expectations for heparin, thus making an important natural product better controlled and less susceptible to economically motivated adulteration.

How one academic medical center has managed potency changes with unfractionated heparin

The United States Pharmacopeia recently changed the standards for unfractionated heparin (UFH) resulting in reduction in potency by about 10 %. Despite the reduction in potency, no new recommendations for UFH dosing were recommended. A retrospective review was conducted on patients receiving UFH and at least one activated partial thromboplastin time (aPTT) after start of infusion. Patients receiving UFH prior to April 2010 were collected as old UFH potency patients versus those receiving UFH after May 1st, 2010 were defined as new UFH potency patients. The primary endpoint was time to a therapeutic aPTT. Secondary endpoints included the number venous thrombotic events (VTE) and bleeding events during hospitalization through 30 days post discharge. Thrombotic events were defined as acute coronary syndrome, ischemic stroke, and VTE. Bleeding was defined in accordance with the GUSTO bleeding scale. A total of 359 patients were included for evaluation, 181 in the old UFH group and 178 in the new UFH group. The primary endpoint was similar between groups with an average time of 18.8 ± 25.4 versus 20.8 ± 22.2 h in the old and new UFH groups respectively (p = 0.092). Patients receiving old UFH and an initial bolus had higher aPTTs (96.6 ± 43.7 s) than those receiving new UFH and an initial bolus (76.7 ± 34.5 s) (p = 0.003). There was no difference found between groups in regards to bleeding or thrombotic events during hospitalization or through 30 days. In patients receiving UFH, dosed per the institutions' nomogram, no clinically significant outcomes were found between the old and new UFH potencies.

Change in heparin potency and effects on the activated clotting time in children undergoing cardiopulmonary bypass

BACKGROUND

Heparin is the anticoagulant most commonly used for cardiopulmonary bypass (CPB), and the activated clotting time (ACT) is its primary monitor. In October 2009, the Food and Drug Administration changed the United States Pharmacopeia (USP) monograph for unfractionated heparin to incorporate new quality tests and a new potency assay and reference standard. This latter change was anticipated by in vitro tests to reduce heparin potency by 10% in each USP unit dose. After integration of the "new" heparin into our practice, we subjectively noticed less prolongation of the ACT with our routine heparin bolus before the initiation of CPB. We performed this investigation to provide objective evidence of a reduction in the level of anticoagulation achieved with use of the new heparin as assessed by ACT values and to document the occurrence of having an ACT below our institutional threshold before the initiation of CPB.

METHODS

A retrospective chart review was performed on all children who underwent CPB at Children's Healthcare of Atlanta between July 1, 2008, and June 30, 2009, before the release of the new heparin ("old heparin" [OH] group) and between June 1, 2010, and May 31, 2011, after complete integration of the new heparin ("new heparin" [NH] group). Baseline ACTs and ACTs after the administration of 400 U/kg of heparin were recorded for both the OH and NH groups. We determined the number of patients in each group having an ACT <480 seconds after the initial heparin bolus but before the initiation of CPB. Additionally, patients were divided into 3 age groups (<1 month, 1 to 12 months, and >1 year) to analyze similar ACT changes.

RESULTS

Postheparin ACTs were significantly lower in the NH group than in the OH group. There were significantly more patients having an ACT <480 seconds after the initial heparin bolus in the NH group (OH: 68 of 557 [12.2%] versus NH: 140 of 491 patients [28.5%]; P < 0.0001). The change remained significant when assessed across the age groups.

CONCLUSIONS

In this investigation we provide objective evidence that the level of anticoagulation after the initial pre-CPB heparin bolus as assessed by the ACT is significantly less with use of the new heparin. This reduction remained consistent across 3 age groups and was associated with a more frequent occurrence of ACTs below our institutional threshold for the initiation of CPB. Consideration should be given to increasing the initial weight-based heparin dose administered before CPB.