June 2007

Antibiotic risk revealed

Researchers have linked vancomycin to an abnormal decrease in blood platelet count, a condition called thrombocytopenia. The study appeared in the March 1, 2007, edition of 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," says Dr. Aster. "Three of the 29 cases described ended fatally. Serious bleeding appears to have contributed to these outcomes."

It is not widely recognized that vancomycin can cause thrombocytopenia. For that reason, the medication was continued in 15 of the 29 patients while other possible causes for the low platelet count were investigated, according to Aster. 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.

"Vancomycin has been in widespread use for more than 25 years and can be a life‑saving medication when used in the appropriate context," says Aster. Since only a small fraction of patients given vancomycin produce antibodies that cause thrombocytopenia, the findings should have no impact on the clinical use of vancomycin."