Effect of inline filtration on delivery of gentamicin at a slow infusion rate

The effects of inline filtration and filter position on delivery of gentamicin at a slow infusion rate were studied. An i.v. infusion system consisting of an infusion pump with syringe, i.v. tubing, and an inline filter was used to simulate i.v. administration conditions in a neonatal intensive-care unit. Three filter sets were studied: Travenol 0.22 micron, Travenol 0.5 micron, and Pall Ultipor 0.2 micron. In separate experiments using each of the three filters, single doses of gentamicin 2.5 mg and 7.5 mg (as the sulfate salt) were injected antegrade to the filter into the system containing 10% dextrose injection. The infusion pump was set at 8.26 ml/hr, and effluent samples were collected at 1, 1.5, 2, and 4 hours after drug administration. To determine the effect of filter position on drug delivery, each filter was studied in four positions: horizontal position with ascending (AH) or descending (DH) fluid flow, and vertical position with ascending (AV) or descending (DV) fluid flow. Drug adsorption to the i.v. tubing was determined by comparing drug recoveries in the infusion system with and without inline filters. Gentamicin concentration in the effluent was expressed as cumulative percentage of the administered dose. No significant adsorption of gentamicin to the i.v. tubing or any of the inline filters occurred at either gentamicin dose. With the Travenol 0.22-micron filter, drug delivery was significantly faster with ascending fluid flow than with descending flow in both positions except at four hours after the dose. Because drug delivery with the two Travenol filters was similar in the AV position, the 0.5-micron filter was not studied in other positions.(ABSTRACT TRUNCATED AT 250 WORDS)