Practical Considerations in Dose Extrapolation from Animals to Humans.

Animal studies are an important component of drug product development and the regulatory review process since modern practices have been in place, for almost a century. A variety of experimental systems are available to generate aerosols for delivery to animals in both liquid and solid forms. The extrapolation of deposited dose in the lungs from laboratory animals to humans is challenging because of genetic, anatomical, physiological, pharmacological, and other biological differences between species. Inhaled drug delivery extrapolation requires scrutiny as the aerodynamic behavior, and its role in lung deposition is influenced not only by the properties of the drug aerosol but also by the anatomy and pulmonary function of the species in which it is being evaluated. Sources of variability between species include the formulation, delivery system, and species-specific biological factors. It is important to acknowledge the underlying variables that contribute to estimates of dose scaling between species.

Inhalation Pharmacodynamics.

Pharmacodynamics (PD) is discussed in relation to inhalation exposure to inhaled pharmaceutical and toxic agents. Clearly PD is closely related to pharmacokinetics, and this relation is illustrated with reference to inhaled insulin. PD can be related to pharmacologic responses, and some examples are cited. However, PD can also be thought of as the improvement or deterioration in lung disease state. Some of the major PD endpoints, including histopathology, pulmonary function, and bronchoalveolar lavage are reviewed. Brief reference is also given to other specialty biomarkers of PD response.

Perspectives on Lung Dose and Inhaled Biomolecules.

Dose is highly important to studies of inhaled agents because there must be an understanding of the dose delivered to humans, the dose delivered to animals in toxicology studies, and an ability to interpret and compare both sets of information relative to safety. Unlike oral or intravenous administrations, total delivered or inhaled dose is not easy to determine following inhalation exposure and is also not necessarily the most important determinant of toxicity. A review of dose distribution throughout the respiratory tract as well as total inhaled dose is provided. The implications of regional deposition for biologics are reviewed and specific examples over a range of different molecular weights are provided. Biologics are generally large enough that absorption from ciliated epithelia is low. Thus, deposition of biologics in head airways and tracheobronchial regions is unlikely to be of high importance unless there are interactions with specific receptors at these sites. Therefore, it is the dose of proteins or biologics deposited in the alveolar region that are generally of most interest.

Inhaled Submicron Particle Paclitaxel (NanoPac) Induces Tumor Regression and Immune Cell Infiltration in an Orthotopic Athymic Nude Rat Model of Non-Small Cell Lung Cancer.

Background: This study evaluated the antineoplastic and immunostimulatory effects of inhaled (IH) submicron particle paclitaxel (NanoPac®) in an orthotopic non-small cell lung cancer rodent model. Methods: Male nude rats were whole body irradiated, intratracheally instilled with Calu-3 cancer cells and divided into six treatment arms (n = 20 each): no treatment (Group 1); intravenous nab-paclitaxel at 5.0 mg/kg once weekly for 3 weeks (Group 2); IH NanoPac at 0.5 or 1.0 mg/kg, once weekly for 4 weeks (Groups 3 and 4), or twice weekly for 4 weeks (Groups 5 and 6). Upon necropsy, left lungs were paraffin embedded, serially sectioned, and stained for histopathological examination. A subset was evaluated by immunohistochemistry (IHC), anti-pan cytokeratin staining AE1/AE3+ tumor cells and CD11b+ staining dendritic cells, natural killer lymphocytes, and macrophage immune cells (n = 2, Group 1; n = 3 each for Groups 2-6). BCL-6 staining identified B lymphocytes (n = 1 in Groups 1, 2, and 6). Results: All animals survived to scheduled necropsy, exhibited no adverse clinical observations due to treatment, and gained weight at the same rate throughout the study. Histopathological evaluation of Group 1 lung samples was consistent with unabated tumor growth. Group 2 exhibited regression in 10% of animals (n = 2/20). IH NanoPac-treated groups exhibited significantly higher tumor regression incidence per group (n = 11-13/20; p < 0.05, χ2). IHC subset analysis revealed tumor-nodule cluster separation, irregular borders between tumor and non-neoplastic tissue, and an increased density of infiltrating CD11b+ cells in Group 2 animals (n = 2/3) and in all IH NanoPac-treated animals reviewed (n = 3/3 per group). A single animal in Group 4 and Group 6 exhibited signs of pathological complete response at necropsy with organizing stroma and immune cells replacing areas presumed to have previously contained adenocarcinoma nodules. Conclusion: Tumor regression and immune cell infiltration were observed in all treatment groups, with an increased incidence noted in animals receiving IH submicron particle paclitaxel treatment.

Pharmacokinetic Profile of Inhaled Submicron Particle Paclitaxel (NanoPac®) in a Rodent Model.

BACKGROUND: Inhaled chemotherapeutics may enhance pulmonary drug exposure to malignant lesions in the lung without substantially contributing to systemic toxicities. The pharmacokinetic profile of inhaled submicron particle paclitaxel (NanoPac®) in healthy rodent plasma and lung tissue is evaluated here to determine administration proof-of-principle. METHODS: Healthy male Sprague Dawley rats received paclitaxel in one of three arms: intravenous nab-paclitaxel at 2.9 mg/kg (IVnP), inhaled NanoPac low dose (IHNP-LD) at 0.38 mg/kg, or inhaled NanoPac high dose (IHNP-HD) at 1.18 mg/kg. Plasma and lung tissue paclitaxel concentrations were determined using ultraperformance liquid chromatography tandem mass spectrometry from animals sacrificed at 10 time points ranging up to 2 weeks after administration. Peak concentration (Cmax), apparent residence half-life (T1/2), exposure (AUC(last)), and dose-normalized exposure (AUCD(last)) were determined. Pulmonary histopathology was performed on rats sacrificed at the 336-hour time point. RESULTS: Paclitaxel was detectable and quantifiable in the rat lung for both inhaled NanoPac arms sampled at the final necropsy, 336 hours postadministration. Substantial paclitaxel deposition and retention resulted in an order of magnitude increase in dose-normalized pulmonary exposure over IVnP. Inhaled NanoPac arms had an order of magnitude lower plasma Cmax than IVnP, but followed a similar plasma T1/2 clearance (quantifiable only to 72 hours postadministration). Pulmonary histopathology found all treated animals indistinguishable from treatment-naive rats. CONCLUSION: In the rodent model, inhaled NanoPac demonstrated substantial deposition and retention of paclitaxel in sampled lung tissue. Further research to determine NanoPac's toxicity profile and potential efficacy as lung cancer therapy is underway.

Comparison of inhalation toxicity studies of gentamicin in rats and dogs.

Nebulized gentamicin solution was administered to rats (nose-only) and dogs (face mask) for 14 days with a 14-day recovery period. Control groups of each were exposed to saline aerosols. Mean estimated inhaled lung doses of gentamicin were 39, 123 and 245 mg/kg for rats (deposited doses 6, 17 and 34 mg/kg) over 30, 90 and 180 min, respectively. Since dogs do not tolerate exposures as long as rats, inhaled lung doses were limited to 7, 14 and 41 mg/kg (deposited doses of 1, 3 and 8 mg/kg) over 15, 30 and 60 min. Comparable doses were achieved at the low dose for rats and high dose for dogs. Serum AUCs (14 ± 2 µg/mL h (mean ± SD) at 6 mg/kg in rats and 11 ± 7 µg/mL h at 8 mg/kg in dogs) showed comparable exposure between the two, implying similar absorbed doses and confirming similar deposited lung doses. Rat exposures resulted in dose-related lung pathology (including low dose) manifested as upper respiratory tract irritant reactions with alveolar histiocytosis, inflammation, airway epithelial metaplasia and lymphomegaly in lung tissue. This was associated with high lung tissue gentamicin levels 24 h post-dose on Day 14 (375 ± 33 µg/g at deposited dose of 6 mg/kg). Dose-related kidney tubular necrosis (a well-known toxicity of parenteral gentamicin) was observed, but no test-article related effects on lung histopathology in dogs (even at highest deposited dose of 8 mg/kg) and low levels of lung tissue gentamicin (42 ± 11 µg/g) 24 h post-dose on Day 14.

The relevance of animal models for aerosol studies.

Animal models are essential for understanding the fates and effects of inhaled materials, because invasive methods are frequently necessary to provide the desired information. Because of the variability in humans of particle deposition, clearance, and effects, numerous animal models have been used in inhalation studies. Furthermore, humans are not typical mammals in some ways that affect inhalation phenomena. Humans have less fur, longer gestation and life times, simplified nasal structure, and symmetric bronchial branching in relation to other mammals. However, experience, plus the genetic similarity among mammals, underpins the use of animal models. Mammals are varied with respect to their inhaled particle deposition and clearance phenomena. Total inhaled aerosol deposition probability versus particle-size curves are qualitatively similar for various mammals of similar body mass, despite airway anatomy differences. However, more species variation is seen in regional particle deposition curves, complicating aerosol study design. The rates of clearance of deposited slowly dissolving particles are animal species dependent, apparently due to differences in gross, subgross, and cellular respiratory tract biology. Clearance rates for rapidly dissolving particles are not strongly species dependent. Inhalation toxicology studies require several animal species. Rodents are among the most frequently used, but for studies of lung development, diseases, exercise, etc., and for extrapolation to humans, larger mammals are also needed. Fortunately, the research database, and excellent monographs on inhalation phenomena provide ample guidance for study design.

A 6-month inhalation study to characterize the toxicity, pharmacokinetics, and pharmacodynamics of human insulin inhalation powder (HIIP) in beagle dogs.

The purpose of this study was to characterize the toxicity, pharmacokinetics, and pharmacodynamics of human insulin inhalation powder (HIIP) in beagle dogs when administered daily as an aerosolized dry powder formulation for 26 weeks via head-only inhalation. Conscious beagle dogs were exposed for 15 mins/day to an air control, placebo, maximal placebo (approximately three-fold the placebo dose), or one of three doses of HIIP (mean inhaled doses of 80, 240, or 701 microg/kg/day for the HIIP-low, HIIP-mid, and HIIP-high dose, respectively), The mass median aerodynamic diameters (MMAD) were between 2 and 3 microm and geometric standard deviation (GSD) values were approximately 2 across the groups, which is the ideal size range for favorable lung deposition. All groups were comprised of four dogs/sex, with the air control, HIIP-high, and maximal placebo groups having an additional two dogs/sex as recovery subgroups. Concentrations of serum insulin and glucose were determined from blood samples obtained following the first and last exposure for evaluation of the pharmacokinetics and pharmacodynamics of HIIP. Dose-related exposure (C(max), AUC) to inhaled insulin was observed with rapid absorption and no apparent gender differences or accumulation after repeated inhalation exposures for 26 weeks. The expected pharmacological effect of insulin was observed with dose-related decreases in serum glucose levels following HIIP administration. There were no toxic effects observed including no HIIP or placebo treatment-related effects on mean body weights, absolute body weight changes, clinical observations, food consumption, respiratory function parameters, ophthalmic examinations, electrocardiograms, heart rates, clinical pathology, or urinalysis. Similarly, there were no HIIP or placebo treatment-related effects on pulmonary assessments that included respiratory function parameters, bronchial alveolar lavage assessments, organ weights, or macroscopic and microscopic evaluations, including lung cell proliferation indices. HIIP was considered to have either low or no immunogenic potential in dogs. The no-observed-adverse-effect level (NOAEL) and maximum tolerated dose were the average inhaled dose of 701 microg insulin/kg/day.

Respiratory function in rats restrained for extended periods: assessment of the effects of bethanecol.

INTRODUCTION: The ICH guideline S7A recommends that the effects of drugs on the respiratory system are evaluated in laboratory mammals prior to administration in man. Previously, animals have been placed in plethysmography chambers for short durations. This study investigates the possibility of restraining animals in chambers for a longer duration to assess respiratory function over extended periods. METHODS: Respiratory function in conscious rats was assessed using plethysmography chambers where the rat body was enclosed in a sealed chamber while the head was free. Thoracic movements were measured by pressure transducers linked to a Buxco amplifier system and respiratory parameters were captured and analyzed by the Notocord HEM data acquisition system. Each animal was subjected to 5 acclimatization sessions of escalating duration (1, 2, 4, 5, and 6 hours (h)) over 5 days prior to testing, with a baseline recording session conducted the day prior to dosing. Animals (8 males/group) were dosed subcutaneously with saline or bethanecol (3, 10, or 30 mg/kg) and placed in the chambers for 6 h of continuous recording. Additionally, a recording session was conducted at 24 h post-dose. RESULTS: Subcutaneous administration of 30 mg/kg bethanecol decreased respiration rate by up to 33% during the first 1.5 h post-dose and increased tidal volume by up to 46% from 0.25 to 1.25 h post-dose when compared to vehicle group data. A decrease in minute volume of up to 33% was observed 0.25 h following administration of the 10 and 30 mg/kg doses. DISCUSSION: These data show a respiratory depression caused by the cholinergic agonist bethanecol, an effect partially compensated for by an increase in tidal volume. This also demonstrates the ability to continuously restrain and record respiratory parameters in conscious rats for up to 6 h without any negative impact on the quality of the data.

Socialização da informação nos serviços de atenção primária em saúde

Trata da questão da socialização nos serviços de atenção primária em saúde. Aborda a problemática da individualização no trabalho dos profissionais da saúde e a necessidade de trabalharem em equipe. Propõe estratégias que possibilitem a criação de um ambiente de trabalho socializador das informações da Unidade Básica de Saúde Ponta Grossa de Porto Alegre.

Foreign particles testing in orally inhaled and nasal drug products.

The International Pharmaceutical Aerosol Consortium on Regulation and Science (IPAC-RS) presents this paper in order to contribute to public discussion regarding best approaches to foreign particles testing in orally inhaled and nasal drug products (OINDPs) and to help facilitate development of consensus views on this subject. We performed a comprehensive review of industry experience and best practices regarding foreign particles testing in OINDPs, reviewed current guidances and techniques, and considered health and safety perspectives. We also conducted and assessed results of an industry survey on U.S. Food and Drug Administration requirements for foreign particles testing. We provide here a result of our review and survey: a summary of industry best practices for testing and controlling foreign particles in OINDPs and proposals for developmental characterization and quality control strategies for foreign particles. We believe that clear consensus-based recommendations and standards for foreign particles testing and control in OINDPs are needed. The proposals contained in this paper could provide a starting point for developing such consensus recommendations and standards.

Evaluation of the survival of bacterial contaminants in an inhalable insulin powder.

Survival and growth of three model test bacterial species (Pseudomonas fluorescens, Staphylococcus epidermidis and Bacillus subtilis), present in the air and/or in the human respiratory tract, were tested in inhalable insulin-lactose powder under optimal relative humidity and temperature conditions (RH = 96% and optimal growth temperature for each bacterium of 26-37 degrees C) as well as representative indoor conditions (RH = 43% and T = 20 degrees C). The bacteria survived from 12 h to 7 days depending on the bacterial species and the test condition. P. fluorescens vegetative cells had the lowest and B. subtilis spores the highest survival rate. It was found that insulin-lactose powder does not support bacterial growth and that higher bacterial survival rate was found under representative indoor conditions. Selected experiments were performed with B. subtilis by adding sterile saliva into insulin-lactose powder to represent a typical condition for inhaler use. Furthermore, two other powders were tested with B. subtilis: one representing an inert powder without any nutrients (glass beads) and the other representing a powder with optimal nutrients (tryptic soy broth powder). The data indicate that the survival rate of B. subtilis did not change after the saliva was added and that the survival in insulin-lactose powder was similar to that in inert powder but lower than in powder with optimal nutrients. These results suggest that bacterial growth on residual powder in the inhaler under patient use conditions is unlikely and therefore the concern for patient safety is remote.