Drug binding by reservoirs in elastomeric infusion devices

Drug binding by an elastomeric infusion device reservoir was assessed by measuring its ability to bind fifteen model solutes. Octanol/water (o/w) and hexane/water (h/w) partition coefficients were regressed against the reservoir's solute equilibrium binding constant to generate a binding model. The reservoir's drug binding ability was calculated with the model and drug partition coefficients, which were determined for seventeen commonly infused drugs including tobramycin, gentamicin, penicillin G, piperacillin, lidocaine, morphine, ceftriaxone, imipenem-cilastatin, amphotericin B, ticarcillin and clavulanate, pentamidine, vancomycin, foscarnet, desferoxamine, acyclovir, fluconazole and vinblastine. Formulations studied included 0.9% Saline and 5% Dextrose. With the exception of lidocaine, imipenem, vinblastine and fluconazole, octanol/formulation and hexane/formulation partition coefficients were too low to be measured for these drugs. Thus, the majority of the drugs, when reconstituted in 0.9% Saline or 5% Dextrose, will not be bound by the reservoirs. The magnitude of drug loss for the most highly bound species, fluconazole, is less than 2%. Therefore the reservoirs used in this study are essentially inert with respect to binding of the drugs evaluated in this study.