Accuracy and efficiency of three methods of preparing piggyback admixtures

The efficiency and accuracy of three methods of preparing i.v. admixtures in small-volume plastic bags were compared. One hundred individual 1-g doses of cephalothin sodium in 50-ml minibags were prepared by each of three methods; the PharmAide Fluid Dispensing System (PAFDS), the Valleylab IV Formulator, and the Viavac vacuum unit, using 20-g, 20-g, and 1-g vials of cephalothin sodium, respectively. For each method, preparation time and cost were recorded. To determine accuracy, a random 10% sample of minibags prepared by each method was assayed for cephalothin concentration by microbiologic assay. The IV Formulator required the least time to prepare 100 doses, followed by the PAFDS and the vacuum unit. Cost data for the three methods were nearly identical, with a difference of only $0.07 per dose between the least and most expensive. The minibags prepared using the vacuum pump and unit-of-use vials were more accurate than those prepared with 20-g vials and the other two methods. However, the initial concentration of the cephalothin sodium vials before transferring to the minibags was not tested. Each method studied was found to have advantages and disadvantages. No one system could be judged best for all situations.