In January 2008, the US Centers for Disease Control and Prevention (CDC), along with the Food and Drug Administration, began
a nationwide investigation of adverse health events associated with the use of heparin. FDA confirmed that serious injuries
and hundreds of deaths have been associated with heparin, a blood-thinning drug that had been manufactured with an active
pharmaceutical ingredient (API) sourced from China (1). In February 2008, Baxter Healthcare recalled multidose and single-dose
vials of heparin sodium for injection, as well as "HEP-Lock" heparin flush products. During this investigation, FDA scientists
identified a previously unknown contaminant, oversulfated chondroitin sulfate (OSCS), in the heparin (2).
In response to this public health crisis, the US Pharmacopeial Convention (USPC), in collaboration with FDA, manufacturers,
and other stakeholders, revised the USP heparin monographs. The revision took place in two stages in order to better protect
the US heparin supply and to help prevent future adulteration. To address the immediate public health risk, Stage 1 monograph
revisions, completed in June 2008, consisted of validating and implementing proton nuclear magnetic resonance spectroscopy
(1H NMR) and capillary electrophoresis (CE) procedures initially developed at FDA to detect OSCS. Stage 2 proposed monograph
revisions include new Identification, Potency, and Impurity tests to better control the quality of heparin API.
Stage 1: Immediate response
The Stage 1 monograph revisions of heparin sodium and heparin calcium incorporated FDA's analytical methods for identifying
OSCS in heparin: 1 H NMR and CE. USPC laboratories validated these methods according to procedures outlined in General Information Chapter <1225>
Validation of Compendial Procedures (3). In addition, USPC proposed appropriate system suitability criteria and specifications and developed two new reference
standards (RS) to support the revised monographs: USP heparin sodium identification reference standard (RS) and USP heparin sodium system suitability RS.
The revised monographs were posted June 18, 2008, on the USPC website (
http://www.usp.org/) as Revision Bulletins and became official immediately. These monographs are referenced on the FDA website as well and have
played an important role in controlling the quality of heparin API in the US (1).
Before posting the heparin Revision Bulletins, USPC solicited feedback from stakeholders by hosting two online meetings in
spring 2008. Industry comments as well as submissions of new and improved analytical methods for characterization of heparin
were critical in shaping the next stage of the monograph revision.
Stage 2: Comprehensive modernization
USPC and involved stakeholders realized that a thorough modernization of the existing monographs would be needed to effectively
ensure the continuing quality of heparin. With this objective, USPC has undertaken a second stage of revisions that will completely
revise the heparin sodium monograph (see Table I).
Table I: Changes to heparin sodium monograph.
The USPC Heparin Ad Hoc Advisory Panel played a critical role in revising the heparin sodium monograph and updating the associated
specifications. The panel consists of industry, academia, and regulatory experts from around the world and is advisory to
USP's Biologics & Biotechnology Blood and Blood Products Expert Committee (BBP EC), which is part of USPC's Council of Experts.
Working closely with FDA, panel members reviewed numerous submissions regarding new and improved analytical procedures for
the characterization of heparin. These procedures first were evaluated for suitability as compendial methods, and when needed,
further validation work was carried out.
Public feedback on the Stage 1 1H NMR method generally was positive, but commenters also recommended that USPC state a clear pass/fail criterion while expanding
the procedure to cover the entire spectral range. The revised procedure covers a spectral window of at least 10 to–2 ppm and
requires identification of four main heparin signals: H1 of N-acetylated glucosamine (GlcNAc)/N-sulfated glucosamine, 6S (signal 1), H1 of iduronic acid 2S (signal 2), H2 of N-sulfated glucosamine S (signal 3), and methyl H of GlcNAc (signal 4). In addition, clear acceptance criteria are spelled
out to control both known and potential contaminants in heparin.
Based on public comments, the advisory panel recommended replacing the CE procedure with an anion-exchange high-performance
liquid chromatography (HPLC) procedure that provides higher resolution between heparin and other impurities. Another consideration
favoring the change is the wide availability of HPLC instruments.
The third Identification test that has been introduced is Antifactor Xa to Antifactor IIa Ratio. This ratio of activities is routinely used to characterize unfractionated heparin as well as to distinguish different forms
of low-molecular weight heparins. For high-quality heparin, the ratio of anti-factor Xa to antifactor IIa should be not less
than 0.9 and not more than 1.1. Manufacturers must perform all Identification tests because they serve orthogonal purposes.