[The effect of topical heparin on histamine-induced wheals. A double-blind study]

Since it is difficult to demonstrate the effectiveness of heparin-containing ointments in the treatment of thrombophlebitis under clinical conditions, a double-blind experimental trial was performed in 18 volunteers. To produce a reproducible inflammation, ten drops of a histamine solution containing 10 mg histamine/100 ml, were applied to an area measuring 4 x 7 cm2 on both forearms of each test subject. Under each drop, the skin was pricked five times. Ten minutes after induction of inflammation, one forearm of each subject was treated in a double-blind randomized manner with an ointment containing heparin (50,000 IU heparin/100 g), the other arm being treated with the heparin-free ointment base. As a criterion of the effectiveness of the ointment, the course of the temperature of the forearms was measured using thermography. Ten minutes after application of the histamine solution, the temperature increased by a mean of about 3 degrees centigrade. After 30 minutes' treatment with heparin-containing ointment, the temperature then decreased by 1.77 degrees C, while that of the forearms treated with heparin-free ointment base decreased by only 1.14 degrees C. The difference was statistically significant (p less than 0.001). Sixty minutes after treatment the differences were still significant at p = 0.012. This study thus demonstrates the effectiveness of heparin-containing ointment in the treatment of histamine-induced inflammation.