Introduction: Dosing of antibiotics in people with cystic fibrosis (CF) is challenging, due to altered pharmacokinetics, difficulty of lung tissue penetration, and increasing presence of antimicrobial resistance. Areas covered: The purpose of this work is to critically review original data as well as previous reviews and guidelines on pharmacokinetics of systemic and inhaled antibiotics in CF, with the aim to propose strategies for optimization of antibacterial therapy in both children and adults with CF. Expert opinion: For systemic antibiotics, absorption is comparable in CF patients and non-CF controls. The volume of distribution (Vd) of most antibiotics is similar between people with CF with normal body composition and healthy individuals. However, there are a few exceptions, like cefotiam and tobramycin. Many antibiotic class-dependent changes in drug metabolism and excretion are reported, with an increased total body clearance for ß-lactam antibiotics, aminoglycosides, fluoroquinolones, and trimethoprim. We, therefore, recommend following class-specific guidelines for CF, mostly resulting in higher dosages per kg bodyweight in CF compared to non-CF controls. Higher local antibiotic concentrations in the airways can be obtained by inhalation therapy, with which eradication of bacteria may be achieved while minimizing systemic exposure and risk of toxicity.

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Background: Pseudomonas aeruginosa ( Pa) is the predominant pulmonary pathogen in patients with cystic fibrosis (CF). Tobramycin nebulization is used for the eradication of Pa infection. Nowadays, tobramycin dry powder inhalation (DPI) is available as well. This study reports the results of eradicating Pa with tobramycin DPI versus nebulization. Methods: Adult CF patients with a Pa isolation between September 2010 and September 2017 from the University Medical Centre Groningen (UMCG), the Netherlands, were included in this retrospective study. Results: In total 27 Pa isolations were recorded. In 13 of these, eradication was attempted with tobramycin, 7 with DPI and 6 with nebulization. DPI eradicated Pa successfully in six isolations (85.7%). Of these, one patient received additional oral ciprofloxacin and one received intravenous ceftazidime. Nebulization eradicated three Pa isolations (50.0%), in two of these, additional oral ciprofloxacin was given. Conclusion: Eradication rates of DPI tobramycin are comparable with those for nebulized tobramycin reported in the literature. This study suggests that DPI tobramycin is an alternative to nebulized tobramycin for eradication of Pa. Trial registration: The Medical Ethics Committee of the UMCG granted a waiver (METC2017-349), as they concluded that this study was not subject to the Medical Research Involving Human Subjects Act. The reviews of this paper are available via the supplemental material section.