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(Circulation. 1998;97:1424.)
© 1998 American Heart Association, Inc.

Correspondence

Unfractionated Heparin Dosing in the FRIC Study

Sarah A. Spinler, PharmD

Associate Professor of Clinical Pharmacy, Philadelphia College of Pharmacy and Science, Adjunct Assistant Professor of Pharmacy in Medicine Cardiovascular Division, University of Pennsylvania, Philadelphia, Pa

To the Editor:

In the recent FRIC study,¹ the subheading on page 65 states "Anti–Factor Xa Activity and aPTT Values in the Acute Phase," but no activated partial thromboplastin time (aPTT) values were provided. Because one of the measures of performance of unfractionated heparin (UFH) dosing is the aPTT achieved, the reader cannot interpret the degree of anticoagulation achieved with UFH if no aPTT values are provided. Because aPTT measurement was mandated per protocol at 6 and 12 hours as well as daily through 48 hours, these median aPTT values should be reported as well as the percentages of patients below and above the target of aPTT of 1.5 times the control value. If dalteparin at a dose of 120 IU/kg twice daily is as good as poorly dosed UFH with no safety advantages, why would one use the more expensive dalteparin?

A separate issue relating to all multicenter studies of anticoagulants that use one mandated range for aPTT measurement (such as 1.5 times control) relates to the lack of standardization of the aPTT ranges to target UFH concentrations as well as variability among reagents used for aPTT measurement at individual centers when the target range is only expressed in seconds (eg, 60 to 85 seconds). Both inconsistencies with aPTT measurement could lead to uninterpretable results with UFH. If all new, more expensive anticoagulants are to be compared with UFH, closer scrutiny of dosing is warranted.

View this table: [in this window] [in a new window]   Table 1. Median aPTT Values

View this table: [in this window] [in a new window]   Table 2. Patients Below, Within, and Above Limits

References

1. Klein W, Buchwald A, Hillis SE, Mohiad S, Sanz G, Turpie AGG, van der Meer J, Olaisson E, Undeland S, Ludwig K. Comparison of low-molecular-weight heparin with unfractionated heparin acutely and with placebo for 6 weeks in the management of unstable coronary artery disease: Fragmin in Unstable Coronary Artery Disease Study (FRIC). Circulation. 1997;96:61–68.[Abstract/Free Full Text]

Response

Werner W. Klein, MD

Medizinische Universitätsklinik Graz, Graz, Austria

The . . . [Full Text of this Article]

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