Influence of Age on Frequency of Vancomycin Dosing: RESULTS
A total of 131 patients were included in the study: 58 cases in the q8h group and 73 controls in the q12h group. The authors believe that these groups represented the entire population of eligible patients during the study period, because it was not possible to identify any additional eligible patients for the time- frame in question.
The most obvious difference between the groups at baseline related to age (Table 1): the mean age of the cases was nearly 10 years younger than that of the controls. This is consistent with the research hypothesis that age influenced vancomycin regimen. Patients in the control group had a higher incidence of hypertension (Table 1), whereas a history of injection drug use was more common in the case group.
Table 1. Characteristics of Patients Receiving Vancomycin for Specified Infections
The most common confirmed or suspected MRSA infection among patients included in the study was osteomyelitis, followed by bacteremia and pneumonia. However, a positive culture confirming the causative organism was available for only 31 (24%) of the 131 patients.
Patients less than 40 years of age were more than 3 times as likely as older patients to require q8h dosing (OR 3.1, 95% CI 1.5-6.3; p = 0.002). Thirty-three (57%) of the 58 cases were less than 40 years old, and 22 (30%) of the 73 controls were less than 40 years old. The logistic regression model was adjusted to take into account predictor variables (concurrent nephrotoxic drugs, diabetes, and sex). Because few or no patients had prescriptions for tacrolimus, cyclosporine, amphotericin B, or contrast dye, these agents were excluded from the logistic regression model.