A strong, independent and positive association between plasma fibrinog
en concentrations and cardiovascular disease has been established. To
determine if phenytoin lowers fibrinogen levels we measured plasma fib
rinogen levels in a subset of participants enrolled in arandomized, pl
acebo-controlled, double-blind clinical trial. Participants received p
lacebo or 100 mg, 200 mg, or 300 mg/day of phenytoin for 14 weeks. Fif
ty-six subjects had post-treatment and 20 had pre- and post-treatment
fibrinogen measurements. The phenytoin-treated subjects with posttreat
ment measurements had a 0.24 g/l (8%) reduction in mean fibrinogen lev
els compared to placebo (p=0.3). Phenytoin may be capable of producing
meaningful reductions in fibrinogen levels.