In vitro approach to study the synergistic effects of tobramycin and clarithromycin against Pseudomonas aeruginosa biofilms using prokaryotic or eukaryotic culture media.

Recurrent Pseudomonas aeruginosa infections involving biofilm formation are frequent in cystic fibrosis, aggravating the respiratory distress. Co-administration of clarithromycin and classical tobramycin could improve the health status of patients. Antibiotic toxicity was assessed on epithelial (CFBE41o(-)) and macrophagic (THP-1) cell lines. Non-toxic concentrations of antibiotics alone or in combination were applied twice daily for 12 days on mature (12-day-old) biofilms of three P. aeruginosa strains, developed either in prokaryotic culture broth [tryptic soy broth (TSB)] or in a eukaryotic cell culture medium (RPMI-FCS) more similar to an in vivo environment. The antibiofilm and bactericidal effects of antibiotics were assessed. No toxicity of tobramycin was observed on eukaryotic cell lines at concentrations up to 500µg/mL, whilst 100µg/mL was selected as the clarithromycin upper safe limit. The amount of biofilm was strongly reduced by 100µg/mL and 500µg/mL tobramycin for each strain in both media, whilst clarithromycin was only effective in RPMI-FBS, with synergistic (PAO1 strain) and additive (PYO2 strain) effects detected when combining tobramycin 4µg/mL and clarithromycin 100µg/mL. Finally, tobramycin at ≥100µg/mL exerted strong bactericidal effects on each strain in both media. Clarithromycin also exerted bactericidal effects on each strain in both media; its effect was weaker than tobramycin in TSB but was similar in RPMI-FBS. Synergistic effects were observed on PAO1 and MUCO biofilms, e.g. when combining tobramycin 4µg/mL and clarithromycin 100µg/mL. These in vitro data show that co-administration of clarithromycin and tobramycin acts synergistically against in vitro P. aeruginosa biofilms.

The Lidose hard capsule formulation of fenofibrate is suprabioavailable compared to the nanoparticle tablet formulation under high-fat fed conditions.

PURPOSE: The therapeutic equivalence of multiple registered fenofibrate formulations, several of which are suprabioavailable and therefore marketed at lower dosage strengths than their reference products, is based on the results of bioequivalence studies. Most of these formulations show a higher bioavailability when taken with a high-fat meal. The relative bioavailability of two of these formulations, the 200 mg Lidose hard capsules and the 145 mg nanoparticle tablets, was assessed when taken with a high-fat meal. METHODS: In this single dose, 2-way, randomized, crossover study, 24 healthy subjects received a 200 mg fenofibrate Lidose hard capsule (Test) and a 145 mg nanoparticle tablet (Reference) under high-fat fed conditions. Plasma concentrations of fenofibric acid were measured up to 72 hours by using a validated LC-MS/MS method. RESULTS: The geometric mean ratios (Test/Reference) and the 90% confidence intervals for AUC0-t and Cmax were 1.37 (131.58 - 142.88) and 1.38 (124.60 - 152.93), respectively. The median (range) Tmax- values of fenofibric acid were 4.5 h (3.0 - 8.0 h) and 3.25 h (1.0 - 6.5 h) after administration of the Lidose hard capsule and the nanoparticle tablet, respectively. CONCLUSION: Under high-fat fed conditions the extent of fenofibrate absorption was 37% higher for the 200 mg Lidose hard capsule compared to the 145 mg nanoparticle tablet, which is exactly as expected based on a mg-to-mg weight basis. The results of the present study underline the importance of assessing bioequivalence of fenofibrate formulations under identical fed conditions, and preferentially after a high-fat meal as this condition represents the worst-case scenario. Furthermore, the results of this study demonstrate that the 145 mg nanoparticle tablet is not bioequivalent to the 200 mg Lidose hard capsule when administered under high-fat meal conditions.