Pharmacokinetic Models for Inhaled Fluticasone Propionate and Salmeterol Xinafoate to Quantify Batch-to-Batch Variability.

Advair Diskus is an essential treatment for asthma and chronic obstructive pulmonary disease. It is a dry powder inhaler with a combination of fluticasone propionate (FP) and salmeterol xinafoate (SX). However, the pharmacokinetics (PK) batch-to-batch variability of the reference-listed drug (RLD) hindered its generic product development. This work developed the PK models for inhaled FP and SX that could represent potential batch variability. Two batches each of the reference and the test product (R1, R2, T1, T2) of Advair Diskus (100 µg FP/50 µg SX inhalation) were administered to 60 healthy subjects in a 4-period, 4-sequence crossover study. The failure of the bioequivalence (BE) between R1 and R2 confirmed the high between-batch variability of the RLD. Non-linear mixed effect modeling was used to estimate the population mean PK parameters for each batch. For FP, a 2-compartment model with a sequential dual zero-order absorption best described the PK profile. For SX, a 2-compartment model with a first-order absorption model best fit the data. Both models were able to capture the plasma concentration, the maximum concentration, and the total exposure (AUCinf) adequately for each batch, which could be used to simulate the BE study in the future. In vitro properties were also measured for each batch, and the batch with a higher fraction of the fine particle (diameter < 1 µm, < 2 µm) had a higher AUCinf. This positive correlation for both FP and SX could potentially assist the batch selection for the PK BE study.

Sensitivity of Pharmacokinetics to Differences in the Particle Size Distribution for Formulations of Locally Acting Mometasone Furoate Suspension-Based Nasal Sprays.

To assess bioequivalence of locally acting suspension-based nasal sprays, the U.S. FDA currently recommends a weight-of-evidence approach. In addition to in vitro and human pharmacokinetic (PK) studies, this includes a comparative clinical endpoint study to ensure equivalent bioavailability of the active pharmaceutical ingredient (API) at the site of action. The present study aimed to assess, within an in vitro/in vivo correlation paradigm, whether PK studies and dissolution kinetics are sensitive to differences in drug particle size for a locally acting suspension-based nasal spray product. Two investigational suspension-based nasal formulations of mometasone furoate (MF-I and MF-II; delivered dose: 180 µg) differed in API particle size and were compared in a single-center, double-blind, single-dose, randomized, two-way crossover PK study in 44 healthy subjects with oral charcoal block. Morphology-directed Raman spectroscopy yielded volume median diameters of 3.17 µm for MF-I and 5.50 µm for MF-II, and dissolution studies showed that MF-II had a slower dissolution profile than MF-I. The formulation with larger API particles (MF-II) showed a 45% smaller Cmax and 45% smaller AUC0-inf compared to those of MF-I. Systemic bioavailability of MF-I (2.20%) and MF-II (1.18%) correlated well with the dissolution kinetics, with the faster dissolving formulation yielding the higher bioavailability. This agreement between pharmacokinetics and dissolution kinetics cross-validated both methods and supported their use in assessing potential differences in slowly dissolving suspension-based nasal spray products.

Mechanistic modeling of generic orally inhaled drug products: A workshop summary report.

In silico mechanistic modeling approaches have been designed by various stakeholders with the goal of supporting development and approval of generic orally inhaled drug products in the United States. This review summarizes the presentations and panel discussion that comprised a workshop session concentrated on the use of in silico models to predict various outcomes following orally inhaled drug product administration, including the status of such models and how model credibility may be effectively established.

Advancements in the Design and Development of Dry Powder Inhalers and Potential Implications for Generic Development.

Dry powder inhalers (DPIs) are drug-device combination products where the complexity of the formulation, its interaction with the device, and input from users play important roles in the drug delivery. As the landscape of DPI products advances with new powder formulations and novel device designs, understanding how these advancements impact performance can aid in developing generics that are therapeutically equivalent to the reference listed drug (RLD) products. This review details the current understanding of the formulation and device related principles driving DPI performance, past and present research efforts to characterize these performance factors, and the implications that advances in formulation and device design may present for evaluating bioequivalence (BE) for generic development.

Scientific and regulatory activities initiated by the U.S. Food and drug administration to foster approvals of generic dry powder inhalers: Bioequivalence perspective.

Regulatory science for generic dry powder inhalers (DPIs) in the United States (U.S.) has evolved over the last decade. In 2013, the U.S. Food and Drug Administration (FDA) published the draft product-specific guidance (PSG) for fluticasone propionate and salmeterol xinafoate inhalation powder. This was the first PSG for a DPI available in the U.S., which provided details on a weight-of-evidence approach for establishing bioequivalence (BE). A variety of research activities including in vivo and in vitro studies were used to support these recommendations, which have led to the first approval of a generic DPI in the U.S. for fluticasone propionate and salmeterol xinafoate inhalation powder in January of 2019. This review describes the scientific and regulatory activities that have been initiated by FDA to support the current BE recommendations for DPIs that led to the first generic DPI approvals, as well as research with novel in vitro and in silico methods that may potentially facilitate generic DPI development and approval.

Scientific and regulatory activities initiated by the U.S. food and drug administration to foster approvals of generic dry powder inhalers: Quality perspective.

Regulatory science for generic dry powder inhalation products worldwide has evolved over the last decade. The revised draft guidance Metered Dose Inhaler (MDI) and Dry Powder Inhaler (DPI) Products - Quality Considerations [1] (Revision 1, April 2018) that FDA issued summarizes product considerations and potential critical quality attributes (CQAs). This guidance emphasizes the need to apply the principles of quality by design (QbD) and elements of pharmaceutical development discussed in the International Conference for Harmonisation of (ICH) guidelines. Research studies related to quality were used to support guidance recommendations, which preceded the first approval of a generic DPI product in the U.S. This review outlines scientific and regulatory hurdles that need to be surmounted to successfully bring a generic DPI to the market. The goal of this review focuses on relevant issues and various challenges pertaining to CMC topics of the generic DPI quality attributes. Furthermore, this review provides recommendations to abbreviated new drug application (ANDA) applicants to expedite generic approvals.

Considerations for the Forced Expiratory Volume in 1 Second-Based Comparative Clinical Endpoint Bioequivalence Studies for Orally Inhaled Drug Products.

Herein, we present the US Food and Drug Administration (FDA) Office of Research and Standards' current thinking, challenges, and opportunities for comparative clinical endpoint bioequivalence (BE) studies of orally inhaled drug products (OIDPs). Given the product-associated complexities of OIDPs, the FDA currently uses an aggregate weight-of-evidence approach to demonstrate that a generic OIDP is bioequivalent to its reference listed drug. The approach utilizes comparative clinical endpoint BE or pharmacodynamic BE studies, pharmacokinetic BE studies, and in vitro BE studies to demonstrate equivalence, in addition to formulation sameness and device similarity. For the comparative clinical endpoint BE studies, metrics based on forced expiratory volume in the first second (FEV1 ) are often the recommended clinical endpoints. However, the use of FEV1 can pose a challenge due to its large variability and a relatively flat dose-response relationship for most OIDPs. The utility of applying dose-scale analysis was also investigated by the FDA but often not recommended, due to either flat dose-response relationships or insufficient clinical study data. As a potential way to reduce sample size, we found adapting covariate analysis only explained a limited portion of the variation based on further investigation. The FDA continues to develop alternative methods to make BE assessment of OIDPs more cost- and time-efficient. Prospective generic drug applicants and academia are encouraged to participate in this effort by proposing new approaches in pre-abbreviated new drug application meeting requests and collaborating in the form of grants and contracts under the Generic Drug User Fee Amendments (GDUFA) Regulatory Science and Research Program.

Medication Cost-Savings and Utilization of Generic Inhaled Corticosteroid (ICS) and Long-Acting Beta-Agonist (LABA) Drug Products in the USA.

BACKGROUND: In the USA, drug costs associated with the inhaled corticosteroid (ICS) and long acting ß agonist (LABA) combination products have been increasing since 2001. In January 2019, the first generic ICS/LABA drug product was approved by the U.S. Food and Drug Administration. METHODS: We investigated retrospectively the effects of the first approved generic ICS/LABA drug from 2019 to 2020 on the wholesale cost-savings and prescription dispensing using the IQVIA data system in the USA. RESULTS: The marketing of the first generic for fluticasone propionate and salmeterol xinafoate dry powder inhaler was associated with $941 million in drug cost-savings during the first year for this class of medications. Although the brand-name drug manufacturer concurrently introduced its authorized generic, these cost-savings were driven by the averaged unit cost of the approved generic at $115, compared to $169 for the authorized generic and $334 for the branded product. Generic initiation and substitution with the first generic were, respectively, higher compared to those with authorized generics; however, overall dispensing of the first generic was lower than that of its branded product. As in the case of budesonide and formoterol fumarate dry powder inhaler, marketing of authorized generics alone was not associated with any noticeable change in sales or prescription cost-saving. CONCLUSION: We estimated that more than 20% of prescription cost-saving was achieved for the ICS/LABA dry powder inhalers in the first year following the introduction of the first approved generic, even though generic utilization remained lower than that of the branded counterpart.

Cyclosporine release and distribution in ophthalmic emulsions determined by pulsatile microdialysis.

An in vitro release test based on pulsatile microdialysis (PMD) is presented for the purpose of measuring the release of cyclosporine from ophthalmic emulsions, along with a method to determine the drug distribution within the oil-rich globule, surfactant-rich micelle and aqueous phases of the emulsion formulation. Compositionally equivalent formulations containing 0.05% cyclosporine were prepared with similar physical parameters (globule size, viscosity, surface tension zeta potential, osmolality, pH) but made with different manufacturing conditions. Emulsions were made by ultrasonication, using different ultrasonication times (22-49 min) and temperatures (50-82 °C). Formulations were stored at room temperature (20 °C) and PMD was performed under two conditions, one in which the receiving medium temperature was 20 °C, and another in which the receiving medium temperature was 35 °C to mimic the temperature change expected when a drop of formulation is administered to the eye. The PMD release data were taken at release times of 20, 40, 60, 90, 120, 180, 300 and 600 s. All experiments showed a qualitatively similar release pattern, with a rapid initial rate of drug release (Release-1) for the first few minutes, followed by a much slower release (Release-2). In addition, imposing a sudden temperature change on the formulation was observed to affect the release, with some formulations releasing faster into receiver media at 35 °C than at 20 °C, while others released faster into 20 °C than 35 °C receiver media. The drug distribution was also calculated from PMD release data into 20 °C receiver media using a novel release kinetics model. The drug distribution varied among the formulations, with 54-77% of the cyclosporine in the oil phase of the emulsions. PMD is a promising method to evaluate how manufacturing-induced differences affect the distribution and release kinetics of cyclosporine within the emulsion formulation.

A Systematic Approach in the Development of the Morphologically-Directed Raman Spectroscopy Methodology for Characterizing Nasal Suspension Drug Products.

Demonstrating bioequivalence (BE) of nasal suspension sprays is a challenging task. Analytical tools are required to determine the particle size of the active pharmaceutical ingredient (API) and the structure of a relatively complex formulation. This study investigated the utility of the morphologically-directed Raman spectroscopy (MDRS) method to investigate the particle size distribution (PSD) of nasal suspensions. Dissolution was also investigated as an orthogonal technique. Nasal suspension formulations containing different PSD of mometasone furoate monohydrate (MFM) were manufactured. The PSD of the MFM batches was characterized before formulation manufacture using laser diffraction and automated imaging. Upon formulation manufacture, the droplet size, single actuation content, spray pattern, plume geometry, the API dissolution rate, and the API PSD by MDRS were determined. A systematic approach was utilized to develop a robust method for the analysis of the PSD of MFM in Nasonex® and four test formulations containing the MFM API with different particle size specifications. Although the PSD between distinct techniques cannot be directly compared due to inherent differences between these methodologies, the same trend is observed for three out of the four batches. Dissolution analysis confirmed the trend observed by MDRS in terms of PSD. For suspension-based nasal products, MDRS allows the measurement of API PSD which is critical for BE assessment. This approach has been approved for use in lieu of a comparative clinical endpoint BE study [1]. The correlation observed between PSD and dissolution rate extends the use of dissolution as a critical analytical tool demonstrating BE between test and reference products.

Influence of in vitro release methods on assessment of tobramycin ophthalmic ointments.

The current investigation was carried out to identify appropriate parameters for measuring the in vitro release of tobramycin (TOB) ophthalmic ointments and to evaluate the feasibility of in vitro release testing methods to assess the product performance. Drug release was assessed using USP dissolution apparatus IV and a modified USP dissolution apparatus I with simulated tear solution (STS) as the dissolution medium. The study variables included temperature, membrane material, source and pore size. The results demonstrated a significant influence of the membrane source and pore size on the release of TOB from the ointments. A dissolution medium temperature of 40 °C was found to be appropriate for the release studies. Both of the apparatuses were able to discriminate between the release profiles of ointments with different physicochemical/rheological properties. Maximum release rate of TOB was observed in the first hour which followed a logarithmic time dependent release. The correlation between the release rates/amounts and yield stress of the ointments was observed in both the dissolution apparatuses. These results support a rational approach to guide the in vitro release testing of TOB ophthalmic ointments.

Addressing the Regulatory and Scientific Challenges with Generic Orally Inhaled Drug Products.

Generic products offer a considerable cost savings for American consumers and the US healthcare industry. While generics for many products have become available, the approval and adoption of generics for orally inhaled drug products (OIDPs) has lagged behind, owing to the difficulties in bringing these complex generic products to the market. As a complex product, OIDP performance is impacted by numerous factors derived from the product's formulation, delivery to a local site of action within the lung, the performance of the device, and the patient population that uses the medication. Therefore, determining equivalence between generic and brand-name OIDPs requires an approach that considers each of these aspects in order to ensure bioequivalence. FDA's recommended aggregate weight-of-evidence approach for generic OIDPs provides a paradigm where studies and conditions, when taken together, establish equivalence in device performance, systemic exposure, and local drug delivery. This review article covers the various aspects of OIDP complexity, the challenges each presents to equivalence, and FDA's efforts to address these challenges and complex drug development as a whole under the Generic Drug User Fee Amendments (GDUFA). The aggregate weight-of-evidence approach, its rationale, and scientific support is also described.

Influence of Manufacturing Process Variables on the Properties of Ophthalmic Ointments of Tobramycin.

PURPOSE: The main purpose of this study was to evaluate qualitative (Q1) and quantitative (Q2) equivalent oleaginous ophthalmic ointments of tobramycin (TOB) with different physicochemical properties and identify critical process/quality attributes using various in vitro methods of characterization. METHODS: Various sources of petrolatum and TOB, and two mixing methods were employed to generate Q1/Q2 equivalent ointments. Characterization studies included content uniformity, microscopy, modulated temperature differential scanning calorimetry (MTDSC), gas chromatography-mass spectrometry (GC/MS), thermogravimetric analysis (TGA) and rheology. RESULTS: The particle size distribution of TOB influenced the content uniformity of ointments. Differences in the MTDSC endothermic and exothermic peaks of TOB suggested the presence of different polymorphic forms. GC/MS revealed variations in the composition and distribution of linear and branched hydrocarbons of petrolatums. Differences were also observed in the TGA derivative weight loss peaks demonstrating differences in the composition of petrolatum that may be the source of the observed variations in the rheological parameters of the ointments. CONCLUSIONS: Source and composition of the petrolatum played a more critical role in determining the rheological properties compared to the method of preparation. Results demonstrated the impact of the source of TOB, excipients and manufacturing processes on the quality attributes of TOB ophthalmic ointments.

In vitro and ex vivo correlation of drug release from ophthalmic ointments.

In vitro drug release testing and ex vivo transcorneal drug permeation can provide valuable information on the performance of the Q1/Q2 equivalent ointments prior to any animal studies. Good correlation between in vitro and ex vivo drug release may be indicative of good in vitro and in vivo correlation. Accordingly, it is important to investigate in vitro as well as ex vivo drug release from Q1/Q2 equivalent ophthalmic ointments and evaluate whether a correlation between these release profiles can be established. Four Q1/Q2 equivalent loteprednol etabonate ointments were prepared using different processing methods and excipient sources. The rheological parameters (crossover modulus and K value) of the four formulations were determined. The in vitro drug release testing of the four ointment formulations were performed using three different apparati (Franz diffusion cells, USP apparatus 2 with enhancer cells and USP apparatus 4 with semisolid adapters). Three models (zero order, logarithmic and the Higuchi model) were used to study the release kinetics of the ointment formulations. The transcorneal (rabbit corneas) permeation studies were performed using spherical joint Franz diffusion cells. The USP apparatus 4 method demonstrated better discriminatory ability compared to the USP apparatus 2 and the Franz diffusion cell methods. The in vitro release profiles of the four Q1/Q2 equivalent ointments with manufacturing differences showed a better fit using the Higuchi model (R2 > 0.98) for all three release testing methods, compared to the other two models. Ex vivo drug release through the rabbit corneas displayed zero order release kinetics. A logarithmic correlation between rheological parameters (crossover and K value) and transcorneal flux were established. In addition, a plot of the in vitro release rate against the ex vivo release flux of the four ointment formulations, yielded a straight line (R2 > 0.98) for all three release methods. Accordingly, the rheological parameters may be useful in predicting in vitro as well as ex vivo release properties.

On the Road to Development of an in Vitro Permeation Test (IVPT) Model to Compare Heat Effects on Transdermal Delivery Systems: Exploratory Studies with Nicotine and Fentanyl.

PURPOSE: At elevated temperatures, the rate of drug release and skin permeation from transdermal delivery systems (TDS) may be higher than at a normal skin temperature. The aim of this study was to compare the effect of heat on the transdermal delivery of two model drugs, nicotine and fentanyl, from matrix-type TDSs with different formulations, using in vitro permeation tests (IVPT). METHODS: IVPT experiments using pig skin were performed on two nicotine and three fentanyl TDSs. Both continuous and transient heat exposures were investigated by applying heat either for the maximum recommended TDS wear duration or for short duration. RESULTS: Continuous heat exposure for the two nicotine TDSs resulted in different effects, showing a prolonged heat effect for one product but not the other. The Jmax enhancement ratio due to the continuous heat effect was comparable between the two nicotine TDS, but significantly different (p < 0.05) among the three fentanyl TDSs. The Jmax enhancement ratios due to transient heat exposure were significantly different for the two nicotine TDSs, but not for the three fentanyl TDSs. Furthermore, the transient heat exposure affected the clearance of drug from the skin depot after TDS removal differently for two drugs, with fentanyl exhibiting a longer heat effect. CONCLUSIONS: This exploratory work suggests that an IVPT study may be able to discriminate differences in transdermal drug delivery when different TDS are exposed to elevated temperatures. However, the clinical significance of IVPT heat effects studies should be further explored by conducting in vivo clinical studies with similar study designs.

Characterization of Temperature Profiles in Skin and Transdermal Delivery System When Exposed to Temperature Gradients In Vivo and In Vitro.

PURPOSE: Performance of a transdermal delivery system (TDS) can be affected by exposure to elevated temperature, which can lead to unintended safety issues. This study investigated TDS and skin temperatures and their relationship in vivo, characterized the effective thermal resistance of skin, and identified the in vitro diffusion cell conditions that would correlate with in vivo observations. METHODS: Experiments were performed in humans and in Franz diffusion cells with human cadaver skin to record skin and TDS temperatures at room temperature and with exposure to a heat flux. Skin temperatures were regulated with two methods: a heating lamp in vivo and in vitro, or thermostatic control of the receiver chamber in vitro. RESULTS: In vivo basal skin temperatures beneath TDS at different anatomical sites were not statistically different. The maximum tolerable skin surface temperature was approximately 42-43°C in vivo. The temperature difference between skin surface and TDS surface increased with increasing temperature, or with increasing TDS thermal resistance in vivo and in vitro. CONCLUSIONS: Based on the effective thermal resistance of skin in vivo and in vitro, the heating lamp method is an adequate in vitro method. However, the in vitro-in vivo correlation of temperature could be affected by the thermal boundary layer in the receiver chamber.

In vitro release testing method development for ophthalmic ointments.

It is essential as well as challenging to develop a reliable in vitro release testing method for determining whether differences in release profiles exist between qualitatively and quantitatively equivalent ophthalmic ointment formulations. There is a lack of regulatory guidance on in vitro release testing methods for ophthalmic formulations. Three different in vitro release testing methods 1) USP apparatus 4 with semisolid adapters; 2) USP apparatus 2 with enhancer cells; and 3) Franz diffusion cells were investigated. Qualitatively and quantitatively equivalent ointments were prepared via hot melting and simple mixing methods using four different sources of excipients (i.e. white petrolatum). The ointment formulations were characterized for content uniformity, particle size, and rheological parameters. All the formulations showed adequate content uniformity and similar particle size. The ointments prepared via the hot melting processes showed higher rheological parameters, as did the ointments prepared using 'white' petrolatum that exhibited a yellowish color. The three in vitro release testing methods were compared and evaluated for reproducibility, discriminatory capability, and correlation with the rheological parameters. Compared with the compendial methods, the non-compendial method (Franz diffusion cells) showed poorer reproducibility. All three methods possessed the ability to discriminate between the ophthalmic ointments with manufacturing differences. However, the USP apparatus 4 method displayed the largest margin of discrimination between the release profiles of the different ophthalmic ointments. In addition, the in vitro release rate obtained using the USP apparatus 4 method showed the strongest logarithmic linear correlation with the rheological parameters (Power law consistency index (K value) and crossover modulus) compared to the other two methods.

Physicochemical attributes and dissolution testing of ophthalmic ointments.

The investigation of semisolid ophthalmic ointments is challenging due to their complex physicochemical properties and the unique anatomy of the human eye. Using Lotemax® as a model ophthalmic ointment, three different manufacturing processes and two excipient sources (Fisher® (OWP) and Fougera® (NWP)) were used to prepare loteprednol etabonate ointments that were qualitatively and quantitatively the same across the manufactured formulations. Physicochemical properties including drug content and uniformity, particle size and distribution, as well as rheological parameters (onset point, crossover modulus, storage modulus and Power law consistency index) were investigated. In addition, USP apparatus 2 with enhancer cells was utilized to study the in vitro drug release characteristics of the ophthalmic ointments. Both manufacturing processes and excipient sources had a significant influence on the physicochemical attributes and the in vitro drug release profiles of the prepared ointments. Ointments prepared via the hot melt processes exhibited higher rheological parameters and lower drug release rates compared to ointments prepared without hot melting. Ointments prepared with OWP demonstrated higher rheological parameters and lower in vitro drug release rates compared to ointments prepared with NWP. A strong correlation between the rheological parameters and in vitro drug release rate was shown using logarithmic linear regression. This correlation may be useful in predicting in vitro drug release from measured physicochemical properties, and identifying the critical quality attributes during the development of ointment formulations.

Navigating sticky areas in transdermal product development.

The benefits of transdermal delivery over the oral route to combat such issues of low bioavailability and limited controlled release opportunities are well known and have been previously discussed by many in the field (Prausnitz et al. (2004) [1]; Hadgraft and Lane (2006) [2]). However, significant challenges faced by developers as a product moves from the purely theoretical to commercial production have hampered full capitalization of the dosage forms vast benefits. While different technical aspects of transdermal system development have been discussed at various industry meetings and scientific workshops, uncertainties have persisted regarding the pharmaceutical industry's conventionally accepted approach for the development and manufacturing of transdermal systems. This review provides an overview of the challenges frequently faced and the industry's best practices for assuring the quality and performance of transdermal delivery systems and topical patches (collectively, TDS). The topics discussed are broadly divided into the evaluation of product quality and the evaluation of product performance; with the overall goal of the discussion to improve, advance and accelerate commercial development in the area of this complex controlled release dosage form.

Heat effects on drug delivery across human skin.

INTRODUCTION: Exposure to heat can impact the clinical efficacy and/or safety of transdermal and topical drug products. Understanding these heat effects and designing meaningful in vitro and in vivo methods to study them are of significant value to the development and evaluation of drug products dosed to the skin. AREAS COVERED: This review provides an overview of the underlying mechanisms and the observed effects of heat on the skin and on transdermal/topical drug delivery, thermoregulation and heat tolerability. The designs of several in vitro and in vivo heat effect studies and their results are reviewed. EXPERT OPINION: There is substantial evidence that elevated temperature can increase transdermal/topical drug delivery. However, in vitro and in vivo methods reported in the literature to study heat effects of transdermal/topical drug products have utilized inconsistent study conditions, and in vitro models require better characterization. Appropriate study designs and controls remain to be identified, and further research is warranted to evaluate in vitro-in vivo correlations and the ability of in vitro models to predict in vivo effects. The physicochemical and pharmacological properties of the drug(s) and the drug product, as well as dermal clearance and heat gradients may require careful consideration.