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The relationship between the elimination constant of gentamicin and the percentage of functioning nephrons in rats cannot be characterized by a simple linear relation. The results support the assumption that gentamicin elimination per residual nephron increased.

Twenty-three patients with various types of recurrent urinary tract infection were treated with a single daily dose of 160 mg gentamicin for eight to nine days. The treatment eliminated bacteriuria in 19 patients. Evaluation of the therapeutical results according to the site of infection showed elimination of bacteriuria in all patients with lower urinary tract infection. Thus a single daily dose of gentamicin can be recommended in recurrent lower urinary tract infection, and also in upper urinary tract infection not associated with a major impairment of renal function.

The therapeutic efficacy of gentamicin given once or three times a day was compared in a model of experimental renal infection in rats. The same amount of gentamicin given either in a single injection or three injections a day produced no statistically significant difference in the treatment of incipient infection. The effect of this mode of administration on advanced infection depended on the length of the therapy. After five days, administration of the same dose given in a single injection or three injections did not result in significant differences. After ten days the therapy proved more effective when gentamicin was injected three times a day. In comparison a single daily dose, amounting to two thirds of the total dose when given three times a day every eight hours, revealed after five days of therapy a statistically significantly lower bacterial count in the kidney than three daily injections of gentamicin.

Pharmacokinetics of intramuscular gentamicin was observed in healty rats, in rats with renal parenchyma reduced to 1/5 of normal and in rats after bilateral nephrectomy. The results obtained support the assumption that in rats gentamicin is excreted only through the kidneys. Reduction of the renal parenchyma to 1/5 of normal is associated with extention of biological half-life only to double the control value. The results support the hypothesis that in the given experimental conditions gentamicin excretion in residual nephrons increases.

A group of 44 patients with various clinical forms of urinary tract infections received a single dose of 300 mg netilmicin i.m. The treatment was efficacious in all patients with infections which were negative in the antibody-coated bacteria test and not complicated by anatomic and/or functional abnormalities of the kidneys and urinary tract. After three weeks the recurrence rate was only 19%. Single-dose treatment also proved very effective against urinary tract infections in renal transplant patients whose infection is almost always located in the lower urinary tract. In contrast, the short-term results of treatment were much poorer in complicated infections and particularly in urinary tract infections which were positive in the anti-body-coated bacteria test; here, the recurrence rate was 67%.