The majority of patients with
venous thromboembolism (VTE) have a considerable long-term risk of recurrence and may require extended duration of
anticoagulant treatment after the initial 3 to 6 months. The decision to extend treatment is based not only on the individual risk of recurrence, but should also consider the potential complications associated with anticoagulation, taking into account that
anticoagulant drugs are among the drugs most frequently associated with hospital admission due to
adverse drug reactions. The most feared complication of oral
anticoagulants is
bleeding, which in some cases may be fatal or may affect critical organs. Case-fatality rates of
bleeding have been reported to be ∼3 times higher than case-fatality rates of recurrent VTE. Even when nonserious,
bleeding may require medical intervention and/or may impact on patient quality of life or working activity. Factors associated with
bleeding during
anticoagulant treatment include, among others, advanced age,
cancer, renal or
liver insufficiency, or concomitant antithrombotic drugs, but no
bleeding risk score is sufficiently accurate for use in clinical practice. Not uncommonly,
bleeding occurs as a complication of
trauma or medically invasive procedures. Nonbleeding complications associated with oral
anticoagulants are unusual, and their relevance is extremely uncertain, and include
vascular calcification, anticoagulation-related nephropathy, and
osteoporosis. Finally, because VTE not uncommonly affects young individuals and the mean age of the population is ∼60 years, the costs associated with extended anticoagulation should not be forgotten. The costs of the drugs need to be balanced against health outcome costs associated with both recurrent VTE and
bleeding.