Once-daily Tobramycin Treatment Does Not Harm Kidneys of CF Patients, Study Says

Once-a-day treatment with the antibiotic tobramycin does not harm the kidneys of patients with advanced cystic fibrosis (CF), a new study has found. Tobramycin taken three times a day was previously linked to acute and chronic kidney failure in CF patients.

The study, “Glomerular and tubular renal function after repeated once-daily tobramycin courses in cystic fibrosis patients,” appeared in the journal Pulmonary Medicine.

Pseudomonas aeruginosa is a common lung infection in patients with CF and is known to greatly worsen their prognosis. With time, the infection often becomes chronic, due to bacterial biofilm production in the lungs, which makes it easier for bacteria to mutate and develop antibiotic resistance. By the age of 18, around 60 percent of patients with CF have a chronic P. aeruginosa infection, according to a previous study.

Physicians often prescribe tobramycin and other aminoglycosides to control P. aeruginosa, but when taken three times a day — as was often the case in the past — they reportedly caused acute and chronic kidney failure. Today, a once-daily treatment is more common, and seems to be just as effective and less toxic to the kidneys.

A German research team wanted to rule out if once-daily intake of tobramycin harms the kidneys. The team enrolled 56 CF patients — all with healthy kidneys — from an outpatient clinic; 46 of them had previously been treated repeatedly once-daily with intravenous tobramycin for P. aeruginosa, but no closer than four weeks before the study. The remaining 10 patients had never been treated with tobramycin. Researchers collected blood and urine samples, and assessed the excretory function (estimated creatinine clearance) of the kidneys.

Results showed that kidney function remained within normal ranges in all patients — with or without previous treatment with tobramycin — though 39 percent of the patients had a mild drop in kidney function. This, however, was not associated with tobramycin treatment.

Previous reports regarding the use of aminoglycosides three times a day in CF patients showed links between treatment and kidney injury, but P. aeruginosa infection itself may also cause kidney failure, the researchers said. A more recent study showed no such links. The German study is the first to analyze kidney function in CF patients exclusively treated with tobramycin once a day. Its findings indicate that even frequent treatment with tobramycin does not necessary lead to kidney injury in CF patients.