Ticlopidine lowers plasma fibrinogen in patients with polycythaemia rubra vera and additional thrombotic risk factors. A double-blind controlled study.

Thirty-seven patients affected by polycythaemia rubra vera (PRV) and with at least one additional thrombotic risk factor (overt vascular disease, diabetes mellitus, treated hypertension, smoking habit, plasma hyperviscosity, hyperfibrinogenemia) were enrolled in a double-blind randomized placebo-controlled study, and 18 were given ticlopidine 250 mg, b.i.d., for 60 days. All the patients had previously been submitted to cytoreduction, and PRV was under control in all cases at the start of the study. During the study, the haematological parameters were controlled every 15 days, and venesection was performed if haematocrit was greater than 46%. Whole blood viscosity, at low and high shear rates, plasma viscosity, and fibrinogen were measured on days 0 and 60. In the ticlopidine group, we recorded a significant 13.14% reduction of the mean fibrinogen level after treatment (390 +/- 63 vs. 449 +/- 97 mg/dl, p less than 0.01). All the other haemorheological parameters were not significantly modified by ticlopidine treatment, nor were there significant modifications recorded in the placebo group. Our study shows that ticlopidine may reduce a probable thrombotic risk factor (hyperfibrinogenemia) in PRV patients.