Generalized osteoporosis is a result of different causes and pathogenic mec
hanisms, which often combine forces to become clinically relevant. Among th
e different exogenic factors, drugs play an important role, frequently in c
onnection with other factors such as immobilization or pregnancy. It has be
en suggested that anticoagulation therapy with heparins or coumarins may in
duce osteoporotic changes or enhance the development of osteoporosis for ot
her reasons. According to in vitro experiments, preclinical trials, and cli
nical investigations, it seems reasonable to assume that heparins induce in
creased bone loss in a time- and dose-related manner. Low-molecular-weight
heparins most likely have less effect on bone turnover when compared to unf
ractionated heparin. Oral anticoagulation therapy with vitamin K-antagonist
s is believed to have a weak effect on induction of osteoporosis, but clini
cal studies are contradictory. In spite of the fact that a relevant effect
of these drugs on the induction of osteoporosis is questionable, it must be
taken into consideration that anticoagulant drugs may enhance the negative
effects on bone density of other risk factors capable of inducing osteopor
osis such as immobilization, pregnancy, or endocrinological disorders.