Time and cost comparison of four methods of filling piggyback bottles.

The time and cost required by four methods of filling piggyback bottles were compared. The four methods compared were (1) the traditional vacuum method, (2) the Wheaton Unispense Model II, (3) the Valleylab IV 6500 Formulator, and (4) the Instafil method. Batches of 20 bottles filled to 50-ml and 100-ml volumes were used to compare fill rates of all four methods. In addition, batches of 60 bottles filled to 100-ml volumes were used to compare the fill time of the Instafil and the IV 6500 Formulator methods. Relative cost factors were then computed for each method and used for comparison. The results showed the Instafil method to be the fastest method for batches of 20 to 60 bottles. The traditional method demonstrated the lowest overall cost, followed by the Instafil method. The authors recommend the use of the Instafil method for batches of 60 or less. For larger batches, an automated device like the Valleylab Formulator or the Wheaton Unispense may be more appropriate.