Pharmacokinetics and safety of tobramycin nebulization with the I-neb and PARI-LC Plus in children with cystic fibrosis: A randomized, crossover study

AIMS

We aimed to compare the pharmacokinetics (PK) and safety profile of tobramycin inhalation solution (TIS) using the I-neb device to the standard PARI-LC Plus nebulizer in children with cystic fibrosis.

METHODS

A randomized, open-label, crossover study was performed. In 2 separate study visits, blood samples from 22 children were collected following TIS nebulization with I-neb (75 mg) and PARI-LC Plus (300 mg). Study visits were separated by 1 month, in which 1 of the study nebulizers was used twice daily. Tobramycin PK for both nebulizers was established using measured tobramycin concentrations and Bayesian PK modelling software. Hearing and renal function tests were performed to test for aminoglycoside associated toxicity. In addition to standard estimated glomerular filtration rate values, biomarkers for tubular injury (KIM-1 and NAG) were measured. Patient and nebulizer satisfaction were assessed.

RESULTS

Inhalations were well tolerated and serum trough concentrations below the predefined toxic limit were reached with no significant differences in PK parameters between nebulizers. Results of audiometry and estimated glomerular filtration rate revealed no abnormalities. However, increased urinary NAG/creatinine ratios at visit 2 for both nebulizers suggest TIS-induced subclinical tubular kidney injury. Nebulization time was 50% shorter and patient satisfaction was significantly higher with the I-neb.

CONCLUSIONS

Nebulization of 75 mg TIS with the I-neb in children with cystic fibrosis resulted in comparable systemic exposure to 300 mg TIS with the PARI-LC Plus and was well tolerated and preferred over the PARI-LC Plus. Long-term safety of TIS nebulization should be monitored clinically, especially regarding the effects on tubular kidney injury.

Colistin methanesulfonate infusion solutions are stable over time and suitable for home administration

The stability of colistin methanesulfonate (CMS) was determined in quadruplicate in elastomeric home infusion pumps containing 1, 2 or 3 MU CMS and in infusion bags with 2 MU CMS all in 100 mL normal saline. Infusions were stored at room temperature (20°C-24°C) with or without exposure to natural light or refrigerated (4°C-8°C) and protected from light up to 2 weeks. In the initial solution of 2 MU CMS in 100 mL saline sampled immediately after reconstitution and dilution, 1.5% of CMS was hydrolysed to colistin. When stored at room temperature and exposed to natural light, colistin concentration in elastomeric infusion pumps increased to 2.6% in 8 days and to 2.1% when stored at 4°C. CMS stability increases at lower temperatures and higher concentrations. Based on the current data, chemical stability of CMS infusion solution is sufficient for a shelf life of 7 days refrigerated plus 1 day at room temperature.