Low Molecular Weight Heparins

Low molecular weight heparins (LMWHs) are a class of blood thinners. Since their introduction in the mid- 1990s they have emerged as effective alternatives to unfractionated heparins. In January 2009, Dr. Doson Chu, a clinical pharmacotherapy specialist at St Paul’s Hospital in Vancouver, turned to CADTH’s Health Technology Inquiry Service (HTIS) to seek information on the characteristics of drugs in this class for specific indications.

LMWHs are used to manage and prevent deep vein thrombosis, pulmonary embolism, and thromboses associated with other conditions. LMWHs prevent the formation of blood clots in blood vessels by reducing the clotting ability of blood.

Although LMWHs have demonstrated comparable or superior efficacy and safety to unfractionated heparins, there is a lack of available data on head-to-head comparisons. Four drugs in this class of blood thinners have been approved in Canada: enoxaparin, dalteparin, tinzaparin, and nadroparin. Each of these LMWHs has distinctive pharmacologic characteristics
(Table 1), the clinical relevance of which, for different indications, is unclear.

CADTH’s HTIS prepared a report that identified a number of randomized head-to-head studies. This report, said Dr. Chu, “succinctly summarized and analyzed the relevant literature and helped determine the selection of a formulary drug in regards to its efficacy, safety and cost impact.”

The HTIS responds to approximately 30 monthly requests that require immediate responses similar to this one.

TABLE 1: Pharmacologic Characteristics of Low Molecular Weight Heparins

Gomez-Outes A. Expert Rev Pharmacoecon Outcomes Res 2006;6(3):249-59.

_{The report is available to Canadian health care decision-makers in the federal government, provincial health ministries, Local Health Integration Networks, regional health authorities, hospitals, and national and federal health care programs in CADTH member jurisdictions: http://cadth.ca/index.php/en/hta/programs/htis.}