Vancomycin May Trigger Dangerously Low Platelet Count

The antibiotic vancomycin, often used in intensive care units (ICUs), has been linked to an abnormal decrease in blood platelet count, according to a new study.

Researchers at the Medical College of Wisconsin (MCW; Milwaukee, USA) and the blood center of Wisconsin's Blood Research Institute (BCW; Milwaukee, USA) obtained clinical information on 29 patients who tested positive for vancomycin-dependent platelet antibodies. The patients were seen at major U.S. hospitals. Since it is not widely recognized that vancomycin can cause thrombocytopenia, the medication was continued in 15 of the 29 patients while other possible causes for the low platelet count were investigated. None of these patients had a rise in the platelet count until the vancomycin was discontinued and an alternative antibiotic started. The vancomycin was stopped early in the remaining 14 patients because it was suspected to be the cause of the thrombocytopenia. The platelet count of these patients rose to normal shortly thereafter. The study was published in the March 1, 2007, edition of the New England Journal of Medicine.

"We found a close correlation between exposure to vancomycin, development of a vancomycin-dependent antibody, and the onset of severe thrombocytopenia accompanied by serious bleeding in most cases,” said lead author Richard H. Aster, M.D., a professor of medicine at the MCW and a senior investigator at BCW. "Three of the 29 cases described ended fatally. Serious bleeding appears to have contributed to these outcomes.”

Thrombocytopenia is defined as less than 150,000 platelets per mm3. Patients with thrombocytopenia bruise easily (platelet counts less than 30-50,000) and, if the platelets are very low (less than 5-10,000), may bleed from areas such as the nose, gums, stomach, and bowel.

Vancomycin is a glycopeptide antibiotic used in the prophylaxis and treatment of infections caused by Gram-positive bacteria. It has traditionally been reserved as a drug of last resort, used only after treatment with other antibiotics had failed.


Related Links:
Medical College of Wisconsin
Wisconsin's Blood Research Institute