Tobramycin therapy of pulmonary infections in patients with cystic fibrosis.

Six patients having exacerbations of chronic pulmonary infections in association with cystic 
fibrosis were treated with intramuscular tobramycin 5 mg./kg./day in 3 divided 
doses. The eight treatment courses lasted 9 to 30 days. Mean 
serum levels were 2.5 microg./ml. at 1 to 3 hours and 
0.2 microg./ml. at 7 1/2 to 8 hours after a dose 
of tobramycin. The mean tobramycin concentration in sputum was 0.3 microg./ml. 
Eighty-two percent of the 66 pathogenic bacterial isolates from sputum were 
either Pseudomonas sp. (64%) or Staphylococcus aureus (18%). Ninety-seven percent of 
Pseudomonas sp. and 83 percent of Staphylococcus aureus were inhibited by 
3.1 microg. tobramycin per ml. No organism that was isolated before 
therapy was observed to become resistant to tobramycin, although on 3 
occasions colonization with new resistant gram-negative bacilli occurred. In 6 out 
of 8 courses of therapy patients showed clinical improvement. Elimination of 
bacterial pathogens from the sputum was rarely achieved and was not 
necessary to produce clinical improvement. Colonization with resistant flora was an 
uncommon finding. Tobramycin's side effects were limited to local discomfort at 
the injection site, nausea and vomiting. 