Can tobramycin inhalation be improved with a jet nebulizer?

The Pharmacokinetics of CPZEN-45, a Novel Anti-Tuberculosis Drug, in Guinea Pigs

CPZEN-45 is a novel compound with activity against drug-susceptible and drug-resistant tuberculosis (TB). The present study was undertaken to determine the best dose and dosing regimen of inhalable CPZEN-45 powders to use in efficacy studies with TB-infected guinea pigs. The disposition of CPZEN-45 after intravenous, subcutaneous (SC), and direct pulmonary administration (INS) was first determined to obtain their basal pharmacokinetic (PK) parameters. Then, the disposition of CPZEN-45 powders after passive inhalation using consecutive and sequential doses was evaluated. Plasma concentration versus time curves and PK parameters indicated that the absorption of CPZEN-45 after INS was faster than after SC administration (Ka = 12.94 ± 5.66 h-1 and 1.23 ± 0.55 h-1, respectively), had a longer half-life (2.06 ± 1.01 h versus 0.76 ± 0.22 h) and had higher bioavailability (67.78% and 47.73%, respectively). The plasma concentration versus time profiles and the lung tissue concentration at the end of the study period were not proportional to the dose size after one, two, and three consecutive passive inhalation doses. Three sequential passive inhalation doses maintained therapeutic concentration levels in plasma and lung tissue for a longer time than three consecutive doses (10 h vs. 3 h, respectively). Future studies to evaluate the efficacy of inhaled CPZEN-45 powders should employ sequential doses of the powder, with one nominal dose administered to animals three times per day.

The pharmacokinetics of antibiotics in cystic fibrosis

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.

Colistin dry powder inhalation with the Twincer™: An effective and more patient friendly alternative to nebulization

Background

Nebulization of antimicrobial drugs such as tobramycin and colistin is a cornerstone in the treatment of patients with cystic fibrosis (CF) infected with Pseudomonas aeruginosa. However, nebulization has a high treatment burden. The Twincer^™ is a dry powder inhaler specifically developed for the inhalation of antibiotics such as colistin. The aim of this study was to compare patient outcomes and experience with colistin dry powder by the Twincer with nebulization of colistin or tobramycin in adult CF patients in a real-life setting.

Methods

This was a retrospective study from 01-01-2015 until 01-07-2018. Effectiveness was evaluated by comparing FEV₁ decline and exacerbation rate during a mean of 4.1 years of nebulization therapy prior to the initiation of the Twincer against the same values during a mean of 1.7 years of treatment with the Twincer.

Results

Twenty-one patients were evaluated, of whom twelve could be included in the effectiveness analysis, with a total of twenty patient years. Of all patients 71.4% preferred therapy with the Twincer over nebulization. Twincer use resulted in high treatment adherence with an average adherence rate of 92.5%. There was no significant difference in annual decline in FEV₁%pred prior to and after start changing from nebulization to the use of the Twincer powder inhaler (median decline -1.56 [-5.57–5.31] and 1.35 [-8.45–6.36]) respectively, p = 0.45 (linear mixed effect model)). No significant difference was found in the number of intravenous or combined total intravenous and oral antibiotic courses during Twincer therapy compared to when using nebulization (1.68 and 2.49 courses during Twincer therapy versus 1.51 and 2.94 courses during nebulization, p = 0.88 and p = 0.63).

Conclusion

Colistin dry powder inhalation with the Twincer is a more patient friendly alternative to nebulization, and we did not observe significant differences in the clinical outcome, regarding lung function and exacerbation rates.

Pharmacokinetics and Tolerability of Once Daily Double Dose Tobramycin Inhalation in Cystic Fibrosis Using Controlled and Conventional Nebulization

BACKGROUND

Better treatment outcomes in cystic fibrosis (CF) may be expected by changing standard twice daily (BID) tobramycin inhalation with the conventional nebulizer to once daily (OD) inhalation at double the standard BID dose with a controlled-inhalation nebulizer. We aimed to determine the pharmacokinetics and tolerability of inhaled double-dose tobramycin with the controlled-inhalation AKITA(®) and conventional PARI-LC(®) Plus nebulizer in patients with CF.

METHODS

Randomized, open label, crossover study. Pharmacokinetics were assessed in 10 adult CF patients following inhalation of tobramycin (Bramitob(®)) at double the recommended BID dose with the AKITA (300 mg fill dose) and PARI-LC Plus (600 mg fill dose).

RESULTS

No significant differences were found in pharmacokinetic parameters between the two nebulizers. Median maximum serum levels were 3.44 (2.25-5.49) and 2.84 (0.82-6.63) mg/L for AKITA and PARI-LC Plus, respectively. Trough serum levels were very low for both nebulizers: 0.03 (0.00-0.09) and 0.02 (0.00-0.06) mg/L for AKITA and PARI-LC Plus, respectively. Time to maximum level was comparable: 0.44 (0.08-0.96) and 0.40 (0.08-0.96) hours for AKITA and PARI-LC Plus, respectively. Serum levels were well below the toxic limit. Inhalations were well tolerated and no serious adverse events occurred. Nebulization time was 33% shorter with the AKITA.

CONCLUSIONS

OD tobramycin inhalation of the double standard BID dose with a controlled-inhalation and conventional nebulizer resulted in similar pharmacokinetics in the doses given, with serum levels below the toxic limit. Further research demonstrating clinical efficacy and safety of this treatment approach is required. Dutch trial register number NTR4525.

Mucin Binding Reduces Colistin Antimicrobial Activity

Colistin has found increasing use in treating drug-resistant bacterial lung infections, but potential interactions with pulmonary biomolecules have not been investigated. We postulated that colistin, like aminoglycoside antibiotics, may bind to secretory mucin in sputum or epithelial mucin that lines airways, reducing free drug levels. To test this hypothesis, we measured binding of colistin and other antibiotics to porcine mucin, a family of densely glycosylated proteins used as a surrogate for human sputum and airway mucin. Antibiotics were incubated in dialysis tubing with or without mucin, and concentrations of unbound antibiotics able to penetrate the dialysis tubing were measured over time using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The percentage of antibiotic measured in the dialysate after 4 h in the presence of mucin, relative to the amount without mucin, was 15% for colistin, 16% for polymyxin B, 19% for tobramycin, 52% for ciprofloxacin, and 78% for daptomycin. Antibiotics with the strongest mucin binding had an overall polybasic positive charge, whereas those with comparatively little binding were less basic. When comparing MICs measured with or without added mucin, colistin and polymyxin B showed >100-fold increases in MICs for multiple Gram-negative bacteria. Preclinical evaluation of mucin binding should become a standard procedure when considering the potential pulmonary use of new or existing antibiotics, particularly those with a polybasic overall charge. In the airways, mucin binding may reduce the antibacterial efficacy of inhaled or intravenously administered colistin, and the presence of sub-MIC effective antibiotic concentrations could result in the development of antibiotic resistance.

Flip-flop pharmacokinetics--delivering a reversal of disposition: challenges and opportunities during drug development

Flip-flop pharmacokinetics is a phenomenon often encountered with extravascularly administered drugs. Occurrence of flip-flop spans preclinical to human studies. The purpose of this article is to analyze both the pharmacokinetic interpretation errors and opportunities underlying the presence of flip-flop pharmacokinetics during drug development. Flip-flop occurs when the rate of absorption is slower than the rate of elimination. If it is not recognized, it can create difficulties in the acquisition and interpretation of pharmacokinetic parameters. When flip-flop is expected or discovered, a longer duration of sampling may be necessary in order to avoid overestimation of fraction of dose absorbed. Common culprits of flip-flop disposition are modified dosage formulations; however, formulation characteristics such as the drug chemical entities themselves or the incorporated excipients can also cause the phenomenon. Yet another contributing factor is the physiological makeup of the extravascular site of administration. In this article, these causes of flip-flop pharmacokinetics are discussed with incorporation of relevant examples and the implications for drug development outlined.

Characterization of a cyclosporine solid dispersion for inhalation

For lung transplant patients, a respirable, inulin-based solid dispersion containing cyclosporine A (CsA) has been developed. The solid dispersions were prepared by spray freeze-drying. The solid dispersion was characterized by water vapor uptake, specific surface area analysis, and particle size analysis. Furthermore, the mode of inclusion of CsA in the dispersion was investigated with Fourier transform infrared spectroscopy. Finally, the dissolution behavior was determined and the aerosol that was formed by the powder was characterized. The powder had large specific surface areas (~ 160 m(2)). The water vapor uptake was dependant linearly on the drug load. The type of solid dispersion was a combination of a solid solution and solid suspension. At a 10% drug load, 55% of the CsA in the powder was in the form of a solid solution and 45% as solid suspension. At 50% drug load, the powder contained 90% of CsA as solid suspension. The powder showed excellent dispersion characteristics as shown by the high emitted fraction (95%), respirable fraction (75%), and fine-particle fraction (50%). The solid dispersions consisted of relatively large (x(50) approximately 7 mum), but low-density particles (rho approximately 0.2 g/cm(3)). The solid dispersions dissolved faster than the physical mixture, and inulin dissolved faster than CsA. The spray freeze-drying with inulin increased the specific surface area and wettability of CsA. In conclusion, the developed powder seems suitable for inhalation in the local treatment of lung transplant patients.

Nebulisers comparison with inhaled tobramycin in young children with cystic fibrosis

BACKGROUND

This randomised cross-over pilot study was undertaken in 10 cystic fibrosis children aged 10 to 63 months to describe lung absorption of tobramycin delivered by the PariLC+/PariTurboboyN (Pari GmbH) and the disposable NL9M/AtomisorBoxPlus (Diffusion Technique Française) nebulising systems.

METHODS

Each child inhaled 300 mg tobramycin delivered with one or the other apparatus via a facemask in two separate and standardised sessions. Urine was collected for 6 h. Tobramycin concentrations determined by immunoprecipitation were expressed in mg per g of creatinine and compared by a Wilcoxon test for matched pairs. The influences of age, weight and Brasfield score on this parameter were evaluated by correlation tests, and those of sex, previous nebulisation treatment, and crying or coughing were evaluated by Student's t-test.

RESULTS

The amount of tobramycin measured in urines was low and variable. Median values for urinary tobramycin concentration were 47.6 mg/g (14.9-79.6) with the PariLC+ and 42.6 mg/g (6.3-112.8) with the NL9M (p=0.6). PariLC+ delivered tobramycin in 22 min and NL9M in 12 min (p=0.005). Crying or coughing dramatically reduced the amount of tobramycin collected.

CONCLUSION

This pilot study shows that evaluation of nebulisers based on tobramycin renal excretion is feasible in young children with cystic fibrosis.

Dry powder inhalation of colistin sulphomethate in healthy volunteers: A pilot study

BACKGROUND

Pulmonary administration of the antimicrobial drugs colistin sulphomethate and tobramycin has been shown to be effective in slowing down pulmonary deterioration in cystic fibrosis (CF) patients. Both drugs are administered by liquid nebulisation, a technique known to have disadvantages. Dry powder inhalation may be an attractive alternative. We investigated inhalation of colistin sulphomethate dry powder using a newly developed Twincer device in healthy volunteers.

METHODS

Eight healthy volunteers inhaled a single dose of 25mg colistin sulphomethate dry powder each, using the Twincer inhaler. The median diameter (X(50)) of the dry powder was 1.6 microm (X(10)=0.7 microm, X(90)=3.1 microm), measured by laser diffraction technique. Pulmonary function tests were performed before, 5 and 30 min after inhalation. Serum samples were drawn at t=15 min, 45 min, 1.5h, 2.5h, 3.5h, 5.5h, 7.5h and 24h after inhalation.

RESULTS

The colistin sulphomethate dry powder inhaler was well tolerated: no clinically relevant effect on FEV(1) was observed nor did the volunteers experience adverse effects.

CONCLUSION

Dry powder inhalation of colistin sulphomethate using the Twincer inhaler is well tolerated by healthy volunteers. A pilot study in cystic fibrosis patients is therefore considered safe in developing a dry powder inhalation of colistin for everyday CF treatment.

Dry powder inhalation versus wet nebulisation delivery of antibiotics in cystic fibrosis patients

Inhalation of antipseudomonal antibiotics is a cornerstone in treating cystic fibrosis patients. It has shown to be effective in slowing down the process of pulmonary deterioration and decreasing the incidence of infectious exacerbations. The focus is now on innovating drug delivery devices, sometimes combined with specific drug formulations, which allow for the administration of large doses in a short time frame and in a reproducible way. Adaptive aerosol delivery devices are promising, but do not have a distinct position as yet because of the lack of long-term data. The position of dry powder inhalation of antibiotics in cystic fibrosis treatment is still confined to pilot studies. Until more clinical data are available, the suboptimal, conventional jet nebulisers are the mainstay in antipseudomonal inhalation therapy in cystic fibrosis.

Dry powder inhalation of colistin in cystic fibrosis patients: a single dose pilot study

BACKGROUND

Dry powder inhalation (DPI) may be an alternative to nebulisation of drugs in the treatment of chest infections in cystic fibrosis (CF) patients. In a pilot study the feasibility of a colistin dry powder inhaler (prototype Twincer) by a single dose in CF-patients was assessed and compared to nebulised colistin.

METHODS

Ten CF-patients, chronically infected with P. aeruginosa, participated in a randomised cross over study. On two visits to the outpatient clinic, patients inhaled colistin sulphomethate as 25 mg dry powder (Twincer) or as 158 mg nebulised solution (Ventstream nebuliser, PortaNeb compressor). Pulmonary function tests were performed before, 5 and 30 min after inhalation. Serum samples were drawn prior to each dose and at 15, 45 min, 1.5; 2.5; 3.5 and 5.5 h after inhalation.

RESULTS

The DPI was well tolerated by the patients: no significant reduction in FEV1 was observed. Relative bioavailability of DPI to nebulisation was approx. 140% based on actual dose and approx. 270% based on drug dose label claim.

CONCLUSIONS

The colistin DPI (Twincer inhaler) is well tolerated and appreciated by CF-patients. Optimisation with respect to particle size and internal resistance of the inhaler is necessary to attain equivalent pulmonary deposition to liquid nebulisation.

Concentrations of gentamicin in serum and bronchial lavage fluid after once-daily aerosol administration to horses for seven days

OBJECTIVE

To assess gentamicin concentrations in serum and bronchial lavage fluid (BLF) of horses during a 24-hour period after once-daily aerosol administration of gentamicin (GAER) for 7 days and the pattern and degree of bronchial tree inflammation associated with repeated GAER.

ANIMALS

13 healthy adult horses (9 geldings and 4 mares).

PROCEDURE

The treatment group comprised 8 horses, and 5 horses were untreated control animals. Gentamicin (20 mL of gentamicin [50 mg/mL]) was administered via aerosol once daily for 7 days. Samples of serum and BLF were obtained from all horses before GAER and 0.5, 4, 8, and 24 hours after the final day of GAER. Gentamicin concentrations were determined for all samples from treated horses, and cytologic examinations were performed on all BLF samples.

RESULTS

Peak median BLF gentamicin concentration detected at 0.5 hours was 2.50 microg/mL. Median serum gentamicin concentration was < 0.50 microg/mL at all time points. Significant differences were not observed in total nucleated cell counts or differential cell counts in BLF between groups at any time point. Neutrophil count in BLF for all horses was increased over baseline at 4 and 24 hours.

CONCLUSIONS AND CLINICAL RELEVANCE

We did not detect evidence of gentamicin accumulation or respiratory inflammation after once-daily GAER for 7 days. This protocol appears unlikely to result in local or systemic toxicosis. Repeated daily GAER to horses appears to be a safe procedure and may have clinical use in the treatment of horses with bacterial infections of the airways.

Dry powder inhalation of antibiotics in cystic fibrosis therapy, part 1: development of a powder formulation with colistin sulfate for a special test inhaler with an air classifier as de-agglomeration principle

The aim of this study was to investigate the pulmonary administration of antibiotics as dry powder to patients with cystic fibrosis (CF), as an alternative for nebulization. This part of the study describes the development of a powder formulation with colistin sulfate as model substance. The aim of the new dosage form was to increase pulmonary deposition, therapeutic efficiency and, by that, compliance by the CF patients. A physical powder mixture of colistin and a size fraction of lactose (106-150 microm) was prepared and the mixture was optimized with respect to colistin content (83.3%) for use in a special test inhaler. A laser diffraction apparatus with special inhaler adapter was applied for analysis of the size distribution of the aerosol cloud from the inhaler. The size distributions of the aerosol clouds from the test inhaler at flow rates between 30 and 60 l/min for the optimized formulation showed nearly the same median diameter as that for the primary drug particles. But the X(100)-value was much lower, because of an effective large particle separation from the inspiratory air by an air classifier in the test inhaler. The results suggest that dry powder inhalation might be a suitable and highly efficient alternative for nebulization of antibiotic drugs in CF therapy.

Dry powder inhalation of antibiotics in cystic fibrosis therapy: part 2. Inhalation of a novel colistin dry powder formulation: a feasibility study in healthy volunteers and patients

The aim of the present study was to perform a proof of principle study with a new colistin dry powder inhalation system in six healthy volunteers and five patients with cystic fibrosis. All subjects were asked to inhale 25 mg colistin sulfate dry powder. The patients were also asked to nebulize 160 mg colistin sulfomethate as a solution. Colistin serum concentrations were determined as an indirect parameter to compare both forms of administration. Pulmonary function tests were performed. Peak serum colistin concentrations ranged from 14 to 59 microg/l in volunteers after inhalation of 25 mg as dry powder. In patients, peak concentrations ranged from 18 to 64 microg/l after nebulization of 160 mg colistin sulfomethate solution and from 77 to 159 microg/l after inhalation of 25 mg colistin sulfate dry powder. Pulmonary function tests were not significantly different after inhalation of the dry powder by the volunteers nor after nebulization of the solution by the patients. In some patients a decrease in pulmonary function and moderate to severe cough was observed after inhalation of the dry powder. The new colistin inhaler provides an attractive alternative for nebulized colistin and was highly appreciated by the patients. The decrease in pulmonary function and cough in patients is a drawback, which may be overcome by dose reduction and a further improvement of the new dosage form.