Background : A vitamin K₂ agent has recently been approved and is going to be marketed for the treatment of osteoporosis. Since vitamin K₂ agents are known to cause rebound of blood coagulation capacity lowered by an anticoagulant warfarin, a great caution is necessary for the concomitant use of these agents.
Objective and Design : A drug utilization survey to examine the use of warfarin and drugs for osteoporosis.
Methods : Fukui Medical School Database was surveyed to identify patients who used warfarin and/or drugs for osteoporosis during the period between January 1, 1988 and July 31, 1995. Patients with a diagnosis osteoporosis made between December 1, 1983 and July 31, 1995, were also identified and their prescription data were extracted to examine the combined use of warfarin and drugs for osteoporosis. In addition, 53 outpatients with cardiovascular diseases were interviewed to know the treatments and medications given by other clinics.
Results : Concomitant drug therapy for osteoporosis was given to 6.9% (56/813) of warfarin users. The proportion of concomitant use was 15% (36/234) in women, much higher than 3.5% (20/579) in men. More than 10% of the interviewed patients were receiving some treatments in other orthopedic clinics for osteoporosis or other diseases but few patients were aware of their medication.
Conclusion : Old female users of warfarin, especially those having osteoporosis concomitantly, are likely to berome a high risk group for the possible interaction between warfarin and the vitamin K₂ agent. Useful information on the safety associated with the interaction between these two drugs should be given to this group of patients as well as to the prescribers and dispensers.