Hematologic impact of antibiotic administration on patients taking clozapine.

Objective: 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.

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

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

Participants: 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.

Measurements And Methods: 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.

Results: 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.

Conclusion: 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.