Intravesical instillation of gentamicin sulfate: in vitro, rat, canine, and human studies

Intravesical instillation of gentamicin sulfate has been used empirically as prophylaxis and to treat bacilluria in spinal-cord-injured patients undergoing clean intermittent catheterization. To assess the risks of absorption and the effects of storage conditions on antimicrobial potency, a series of studies were conducted.

Four studies were carried out: (1) An infected fulgurated rat bladder model was created to determine the effects of inflammation and infection on absorption. (2) A canine model with bilateral vesicoureteral reflux and elevated bladder pressures (> 40 cmH2O) assessed the effects of reflux and storage pressure. (3) The effects in patients with associated conditions including renal transplantation, myelomeningocele, vesicoureteral reflux, and bladder augmentation, were analyzed. (4) To determine the effects of storage conditions, solutions of gentamicin sulfate (480 mg gentamicin sulfate in 1 L 0.9% NaCl) were made that controlled for pH, storage temperature, and duration.

(1) Increased absorption was found in 43 percent of rat serum samples. (2) None of the dogs demonstrated measurable absorption. (3) None of the patients likewise had measurable absorption. (4) All solutions were equally potent when tested against a panel of common urinary pathogens. Storage up to two months at room temperature without alkalinization had no effect on potency.

Instilled intravesical gentamicin sulfate has a low risk of absorption and is highly effective. Severe bladder inflammation can increase transvesical absorption. It has prolonged stability without special storage conditions and should be considered as a route of prophylaxis in patients who perform intermittent catheterization.