Reactive thrombocytosis associated with enoxaparin.

A 42-year-old man was hospitalized for a closed head injury caused by a bicycle accident. On hospital day 8, he developed thrombocytosis. Eleven days later, his platelet count reached 1005 x 10(3)/mm(3). A review of his drug therapy indicated enoxaparin as a potential reversible cause of reactive thrombocytosis. Enoxaparin was discontinued, and the patient's platelet count declined, eventually normalizing 6 days later. At that time, enoxaparin was restarted; this resulted in an increase in his platelet count that peaked 8 days later at 920 x 10(3)/mm(3). After each occurrence of thrombocytosis, enoxaparin was switched to unfractionated heparin in combination with sequential compression devices for deep vein thrombosis prophylaxis. No complications secondary to thrombocytosis were noted. Our patient's experience suggests that unfractionated heparin may be substituted for enoxaparin if this adverse effect is suspected.