Pharmacoeconomics of low-molecular-weight heparins: limitations of studies comparing them to unfractionated heparin.

Unfractionated heparin (UFH) entered medical usage in the 1930s and was the mainstay of acute anticoagulation until the 1980s, when low-molecular-weight heparins (LMWHs) became available. At this time, the acquisition cost of LMWHs, being greater than that of UFH, was a significant barrier to their use even though there was evidence that this was offset by savings in monitoring and other areas. Evidence of the superiority of LMWHs over UFH in many clinical settings has been accumulating and, along with economic analyses that have demonstrated overall cost savings when LMWH is compared to UFH, has resulted in rapidly expanding sales of LMWH, whereas sales of UFH, are in decline. In addition to being more effective than UFH, LMWHs may cause less bleeding, are less likely to cause heparin-induced thrombocytopenia (HIT) and exhibit less inter-patient variability. In addition to the savings from reduced monitoring, the greater acquisition costs for LMWHs are also offset by reduced costs of treating adverse effects and unprevented venous thromboembolism. LMWHs are usually administered once daily via the subcutaneous route, and this often allows treatment to be undertaken in the community rather than in hospitals, thereby saving considerable sums on inpatient costs. Pharmacoeconomic analyses are limited by a variety of factors including geographical and temporal variability in cost inputs, cost shifting, cost inputs that are omitted and payer perspective. Some of these limitations, including the economic impact of HIT and the savings in hospital costs, will be discussed. The effect of changes in acquisition costs since their introduction and the potential impact of medicolegal costs, will also be explored. Settings where evidence of benefit of LMWH over UFH is lacking will also be discussed.