Effect of inline filtration on the potency of low-dose drugs.

Simulating actual conditions of intravenous infusion, a number of routinely used additive drugs were tested for potential binding to an inline i.v. filter containing a cellulose ester membrane. Two infusion solutions, 5% dextrose and 0.9% sodium chloride, were used to deliver the drugs. Drug samples were assayed before and after passage through the filter by the following methods: bleomycin sulfate, cyanocobalamin, ergonovine maleate, mithramycin, vinblastine sulfate, and vincristine sulfate by direct spectrophotometry; oxytocin by biological assay; levarterenol by fluorescence; and folic acid, heparin, insulin, and digitoxin by radiotracer methods. Measurable reduction in potency occurred in both infusion solutions with digitoxin, insulin, mithramycin, and vincristine sulfate. No reduction in potency was observed in either infusion solution with bleomycin sulfate, cyanocobalamin, ergonovine maleate, folic acid, heparin, leverterenol bitartrate, oxytocin, and vinblastine sulfate. The study results indicate that the potency of drugs administered intravenously in small doses could be significantly reduced during inline filtration through a filter containing a cellulose ester membrane.