Efficacy, safety, and local pharmacokinetics of highly concentrated nebulized tobramycin in patients with cystic fibrosis colonized with Pseudomonas aeruginosa.

BACKGROUND AND AIM: Progressive respiratory failure due to Pseudomonas aeruginosa colonization is the most significant morbidity in patients with cystic fibrosis (CF). This trial was designed to investigate the efficacy and safety of a highly concentrated (300mg/4mL) tobramycin solution for inhalation (TSI) [Bramitob] in patients with CF and P. aeruginosa infection. METHODS: Fifty-nine patients were randomized to receive a 4-week treatment with tobramycin or placebo administered twice daily via the Pari LC Plus nebulizer and Pari TurboBoy compressor, followed by a 4-week run-out phase. Pulmonary function (forced expiratory volume in 1 second [FEV(1)], forced vital capacity [FVC], and forced expiratory flow at the midportion of vital capacity [FEF(25-75%)]), P. aeruginosa susceptibility, microbiologic results, and in vitro minimum inhibitory concentration for 90% of strains (MIC(90)) were the efficacy outcome measures, while safety was monitored by the recording of adverse events, audiometry (bone conduction at 250-8,000Hz frequency), laboratory tests, physical examination and general health condition. The concentration of tobramycin attained in sputum was measured in a cohort of 21 patients. RESULTS: FEV(1) significantly increased from baseline in the tobramycin group compared with no change in the placebo group: the absolute difference between groups (intent-to-treat population) of predicted normal was 13.2% at week 2 (p = 0.002) and 13.3% at week 4 (p = 0.003). Significant differences in favor of the tobramycin group were also observed for FVC and FEF(25-75%). The microbiologic results at the end of the treatment period (P. aeruginosa-negative culture, persistence, superinfection) showed a significantly better outcome in the tobramycin group compared with placebo (p = 0.033). The effects of tobramycin on pulmonary function and microbiology were not maintained at the end of the run-out phase. Mean sputum concentrations of tobramycin after the first dose (695.6 +/- 817.0 microg/mL) were similar to those measured after the last dose (716.9 +/- 799 microg/mL) and were superior to the detected specific MIC(90). The proportion of patients with drug-related adverse events was lower in the tobramycin group and no signs of renal or auditory toxicity were observed. CONCLUSIONS: The 4-week administration of a highly concentrated TSI significantly improved pulmonary function and microbiologic outcome compared with placebo and was well tolerated. The results of this study should be confirmed in further long-term trials in larger populations.

A new insertion/deletion of the cystic fibrosis transmembrane conductance regulator gene accounts for 3.4% of cystic fibrosis mutations in Sardinia: implications for population screening.

Previous studies performed on Sardinian patients affected by cystic fibrosis (CF) have led to the identification of molecular defects in 87 of 88 patients. Two mutations, the F508del and T338I, were quite prevalent and accounted for 50% and 20% of the molecular defects, respectively. T338I has been detected rarely in other populations, most likely because of the genetic isolation of Sardinians. In the present study, we have performed a molecular analysis of the CF gene in eight Sardinian patients in whom only a single mutation has been defined. Using DNA analyses (Southern blot, single nucleotide polymorphisms, microsatellite analyses, and Extra-Long polymerase chain reaction) selected to detect gross gene rearrangement and by using mRNA studies, we detected a novel mutation c.54-5811_164 + 2186del8108ins182 in six of the eight patients investigated. This mutation consists of a gross deletion of 8108 bp spanning exon 2 with an insertion of 182 bp at the deletion junction, between nucleotide 54-5811 of intron 1 (IVS1 nt16864) and nucleotide 164 + 2186 of intron 2 (IVS2 nt 2186). By including the novel mutation in our mutation panel we are now able to reach a 95% detection rate, thereby improving the process of carrier detection and genetic counseling in Sardinia.