A placebo or the antimalarial agent hydroxychloroquine (Plaquenil),
which inhibits platelet adhesiveness, and, to a lesser extent, platelet
aggregation, was given to 100 patients between forty and ninety-five years
old (average age, seventy-four years) who had either fractures or
orthopaedic operations involving the skeleton between the knee and the
pelvis. Medication was started at the time of admission in a blind,
randomized way, fifty patients receiving hydroxychloroquine (200 milligrams
three times a day) and fifty, a placebo. No untoward bleeding complications
were noted in the treated group. Eight instances of thromboembolism were
encountered in the control group as compared with one in the
hydroxychloroquine-treated group, a statistically significant difference at
the 1.5 per cent level.