Hematologic impact of antibiotic administration on patients taking clozapine

The purpose of this study was to determine if the drop in white blood cell/absolute neutrophil count for clozapine patients on antibiotics is a normal response to the resolution of infection or if the concurrent administration resulted in an abnormal drop in blood counts and further reduction of white blood cell/absolute neutrophil below baseline prior to infection.

This was a retrospective record review of all patients who received clozapine and antibiotics concurrently between June 30, 2010, and June 30, 2011.

Subjects included inpatients on clozapine therapy at a state psychiatric facility.

This protocol was approved by the Institutional Review Board of record. A total of 42 patients prescribed 93 antibiotic regimens were found to meet all of the above requirements.

Medications were placed into distinct groups based on approved use and mechanism of action. Pearson Correlation Coefficients were utilized and were found to be 0.409 (p<0.01), indicating that a statistically significant relationship existed between the use of systemic antibiotics and alterations in hematologic parameters.

Each regimen was classified by specific agent as well as whether the final white blood cell/absolute neutrophil was above or below the baseline established for each patient.

Antibiotics have been identified as one category of medications that may cause decreased white blood cell/absolute neutrophil counts when combined with clozapine. Our study supports the use of either ciprofloxacin or moxifloxacin as agents that may have less risk of reductions in white blood cell/absolute neutrophil counts than are seen with penicillins, cephalosporins, and other antibiotics that may ultimately require interruption or discontinuation of clozapine therapy.