Ann Tronde

Mechanisms for absorption enhancement of inhaled insulin by sodium taurocholate

The effects of sodium taurocholate (NaTC) on the absorption of inhaled insulin was investigated using both in vivo and in vitro experiments. The absolute bioavailability of insulin when given as a nebulized solution (0.6 mM) to anesthetized intubated beagle dogs was low (2.6+/-0.3%). However, when NaTC at different concentrations (2-32 mM) were included in the formulations the bioavailability increased and at 32 mM it was about nine times higher (23.2+/-4.4%) than for pure insulin. In a similar concentration interval (20-25 mM) NaTC decreased the transepithelial electrical resistance (TEER) across Caco-2 cell monolayers leading to an increased permeability of insulin. At higher concentrations (above 30 mM) the viability of the Caco-2 cells decreased and the insulin permeability increased dramatically. Furthermore, we show that NaTC in the concentration range 2-15 mM gradually decreases the aggregation state of insulin, i.e., produces mono- or dimeric insulin from hexameric insulin. In conclusion, NaTC increases the bioavailability of nebulized insulin, increases the permeability of insulin across Caco-2 cell monolayers, and decreases the aggregation state of insulin at similar concentrations. We suggest that the main mechanisms behind the absorption enhancement of inhaled insulin by NaTC are the production of insulin monomers and an opening of tight junctions between adjacent airway epithelial cells.

Miniaturized nebulization catheters: A new approach for delivery of defined aerosol doses to the rat lung

A nebulization catheter technique (AeroProbe) was adapted and evaluated as a new approach for pulmonary delivery of defined aerosol doses to the rat lung. The lung distribution profile was evaluated by dosing Evans blue and Nile blue dye, respectively, to isolated and perfused rat lungs (IPL) and to the lungs of anesthetized and tracheal-intubated rats. The intratracheal aerosol dosing was synchronized with the inspiration of the lungs. Immediately after dosing, the lungs were dissected into upper- and lower trachea, bronchi, and parenchyma. The dye was then extracted from the tissue samples to determine the regional distribution and the recovery of the aerosol dose in the lungs. The droplet-size distribution and the weight of the delivered aerosol dose were analyzed with laser diffraction and gravimetric analysis respectively. The recovery of the delivered dose was high, 99 +/- 12 and 105 +/- 1%, respectively, in the in vivo administrations and IPL-experiments. The lung distribution profile after aerosol dosing to anesthetized rats was mainly tracheobronchial. Only 12 +/- 4% of the dose was recovered in the lung parenchyma. However, after aerosol dosing to the IPL, 38 +/- 11% of the dose was distributed to the lung parenchyma. At the settings used, the nebulization catheter aerosolized 1-2 microL of liquid per puff using 1-1.5 mL of air. The droplet-size distribution of the generated aerosols was broad (2-8% <3 microm; 10% <4-7 microm; 50% <10-15 microm; and 90% <20-40 microm). The nebulization catheter technique provides a complement to existing methodology for pulmonary drug delivery in small animals. With this new technique, defined aerosol doses can be delivered into the lungs of rats with no need for aerosol dosimetry.

A miniaturized nebulization catheter for improved gene delivery to the mouse lung.

The available methods for administration of gene delivery systems to the lungs of small animals via nebulization have several drawbacks. These include lack of control over the delivered dose and a negative impact on the stability of the formulation. This paper describes a new nebulization catheter device for the administration of plasmid‐based gene delivery systems (polyplexes) as aerosols to the mouse lung in vivo.

Pharmacokinetics of Budesonide and Formoterol Administered Via 1 Pressurized Metered-Dose Inhaler in Patients With Asthma and COPD

In 3 open‐label studies, the systemic bioavailability of budesonide and formoterol administered via pressurized metered‐dose inhaler (pMDI) or dry powder inhaler (DPI) formulations was evaluated in asthma (24 children, 55 adults) or chronic obstructive pulmonary disease (COPD; n =26) patients. Treatments were administered at doses high enough to estimate pharmacokinetic parameters reliably. Two of the studies included an experimental budesonide pMDI formulation. In study 1 (asthma, adults), budesonide area under the curve (AUC) was 32% and 31% lower and maximal budesonide concentration (Cmax) 45% and 56% lower after budesonide/formoterol pMDI and budesonide pMDI versus budesonide DPI. Formoterol AUC and Cmax were 13% and 39% lower after budesonide/formoterol pMDI versus formoterol DPI. In study 2 (asthma, children), budesonide AUC and Cmax were 27% and 41% lower after budesonide/formoterol pMDI versus budesonide DPI + formoterol DPI. In study 3 (COPD/asthma, adults), budesonide AUC and Cmax were similar and formoterol AUC and Cmax 18% and 22% greater after budesonide/formoterol pMDI versus budesonide pMDI + formoterol DPI (COPD). Budesonide and formoterol AUC were 12% and 15% higher in COPD versus asthma patients. In conclusion, systemic exposure generally is similar or lower with budesonide/formoterol pMDI versus combination therapy via separate DPIs or monotherapy and comparable between asthma and COPD patients.

Regional differences in bioavailability of an opioid tetrapeptide in vivo in rats after administration to the respiratory tract

TArPP (Tyr-D-Arg-Phe-Phe-NH(2)), 1-10 micromol/kg, was administered to anesthetized rats by nasal microinfusion, intratracheal microinfusion, intratracheal nebulization, aerosol inhalation, and i.v. bolus and infusion. Plasma concentrations of TArPP and its deamidated metabolite were determined by LC-MS-MS. Regional differences in bioavailability (F), first-pass metabolism, and absorption rate were found for TArPP after delivery to the respiratory tract. Absorption was rapid after both pulmonary and nasal administration (t(max) approximately 10-20 min). After nasal microinfusion, F was 52 +/- 9%. For all the pulmonary groups, F was higher (72-114%). First-pass metabolism of TArPP was lower in the lung than in the nasal cavity. It is evident that the pulmonary route is attractive for successful systemic delivery of small, hydrophilic and enzymatic susceptible peptides.

High airway-to-blood transport of an opioid tetrapeptide in the isolated rat lung after aerosol delivery.

The airway-to-blood absorption of the mu-selective opioid tetrapeptide agonist Tyr-D-Arg-Phe-Phe-NH(2) (MW 631) was investigated in the isolated, perfused, and ventilated rat lung model. The lung metabolism of the peptide was compared after airway and vascular delivery. The concentrations of the parent tetrapeptide and five of its metabolites in the perfusate and in bronchoalveolar lavage fluid were analyzed by LC-MS. The metabolism of the peptide was higher after delivery to the airways compared to vascular delivery. However, the tetrapeptide was highly transported from the air-to-blood side to an extent of 47.8 +/- 10.7% in 2 h. In conclusion, the results prompt investigations of the pulmonary route as a successful alternative to parenteral delivery for this tetrapeptide.

Pharmacokinetics of budesonide and formoterol administered via a series of single-drug and combination inhalers: four open-label, randomized, crossover studies in healthy adults.

Objective: To investigate the pharmacokinetics of budesonide and formoterol administered concomitantly in healthy adults.

The Isolated Perfused Lung for Drug Absorption Studies

Over the past 20 years, the isolated perfused lung (IPL) technique has been developed for the evaluation of pulmonary drug absorption and disposition. The procedure for establishing the model requires a skilled operator, a validated technique for intra-tracheal drug delivery and a system for maintenance and monitoring of the preparation. Most absorption studies to date have utilised the ex vivo rat lung maintained by ventilation and perfusion in an artificial thorax. Techniques for delivery of drugs into the airspaces of the IPL have been developed and the drug transfer (air-to-perfusate) profiles of a variety of actively and passively transported compounds have been measured. Recent developments include the reporting of in vitro-in vivo correlation for air-to-perfusate transfer in the IPL with pulmonary absorption in the rat in vivo, the use of the IPL to model active transport mechanisms and the use of a human lung reperfusion model. The value of the IPL is in discerning lung-specific drug absorption and disposition kinetics that may be difficult to interpolate from in vivo data and cannot be modelled with physiological relevance using reductive in vitro techniques such as cell culture.