Effects of opiates on blood rheology.

To evaluate the possible effect of opiates on blood rheology, the plasma fibrinogen, prothrombin time and leukocyte aggregation were measured in 75 heroin addicts categorized by the time of abstention from heroin and the administration of naltrexone (25 active heroin abusers, 25 abstaining for 1 week, 11 abstaining for at least 5 months and 14 abstaining for 1 month and taking naltrexone during this period). No difference was detected in prothrombin time, but the leukocyte aggregation and fibrinogen were significantly different among the four groups (p = 0.028 and p = 0.0001, respectively). In particular, fibrinogen was 318 +/- 10.9 mg/dL in heroin abusers, significantly higher than that of the remaining three groups; the percentage of aggregated leukocytes was 5.01 +/- 0.77 in heroin users, significantly higher than that of subjects abstaining for at least 5 months. The fibrinogen levels declined sharply with abstention and an additive effect was noted with the administration of naltrexone, but leukocyte aggregation changed more slowly, and the effect of naltrexone (if any) was weaker. These data indicate an adverse effect of opiates on blood rheology and suggest that further studies should be performed to evaluate whether naltrexone may be useful in the prevention of major ischemic syndromes in patients with hyperfibrinogenemia and, perhaps, in those with high levels of leukocyte aggregation.