Considerations in establishing bioequivalence of inhaled compounds

The impact of unsupervised and unconsented switch of inhalers in patients with controlled asthma - A targeted literature review

Inhaler combination formulations consisting of an inhaled corticosteroid (ICS) (fluticasone propionate) and a long-acting β2 agonist (salmeterol xinafoate) are indicated as maintenance treatments for patients with asthma and/or for selected patients with chronic obstructive pulmonary disease. The emergence of generic equivalents to branded inhalers is expected to offer economic edge/savings; however, some may argue that cost advantages offered by generic inhalers may be offset by worsening outcomes due to improper inhaler use, reduced adherence, and consequently worse disease control. To understand how unsupervised and unconsented switch of dry-powder inhalers and/or metered-dose inhalers affects clinical and humanistic outcomes in asthma, comprehensive searches of Embase and MEDLINE were conducted to identify research articles published in the English language since 2011. Patients with asthma of any age who underwent an unsupervised and unconsented switch from an ICS/long-acting β2 agonist to another (brand-to-generic or brand-to-brand) for non-medical reasons were the target of this research. Relevant outcomes included asthma control, medication adherence, and healthcare resource utilization. In total, 11 studies were identified for review (ten non-interventional and one post hoc); cohorts ranged from 19 to 42,553 patients. Six studies indicated that unsupervised and unconsented inhaler switch had a negative impact on asthma control; six studies indicated reduced medication adherence post-switching; and five studies reporting healthcare resource utilization showed it was unchanged or increased post-switching. Findings from this targeted review support concerns that unsupervised and unconsented inhaler switch has a largely negative impact on asthma-associated outcomes. Additional studies are warranted to further explore unsupervised and unconsented switch in asthma.

A new method for investigating bioequivalence of inhaled formulations: A pilot study on salbutamol

Purpose: An efficient, cost-effective and non-invasive test is required to overcome the challenges faced in the process of bioequivalence (BE) studies of various orally inhaled drug formulations. Two different types of pressurized meter dose inhalers (MDI-1 and MDI-2) were used in this study to test the practical applicability of a previously proposed hypothesis on the BE of inhaled salbutamol formulations. Methods: Salbutamol concentration profiles of the exhaled breath condensate (EBC) samples collected from volunteers receiving two inhaled formulations were compared employing BE criteria. In addition, the aerodynamic particle size distribution of the inhalers was determined by employing next generation impactor. Salbutamol concentrations in the samples were determined using liquid and gas chromatographic methods. Results: The MDI-1 inhaler induced slightly higher EBC concentrations of salbutamol when compared with MDI-2. The geometric MDI-2/MDI-1 mean ratios (confidence intervals) were 0.937 (0.721-1.22) for maximum concentration and 0.841 (0.592-1.20) for area under the EBC-time profile, indicating a lack of BE between the two formulations. In agreement with the in vivo data, the in vitro data indicated that the fine particle dose (FPD) of MDI-1 was slightly higher than that for the MDI-2 formulation. However, the FPD differences between the two formulations were not statistically significant. Conclusion: EBC data of the present work may be considered as a reliable source for assessment of the BE studies of orally inhaled drug formulations. However, more detailed investigations employing larger sample sizes and more formulations are required to provide more evidence for the proposed method of BE assay.

Generic dry powder inhalers bioequivalence: Batch-to-batch variability insights

Active pharmaceutical ingredient(s) [API(s)] of dry powder inhalers (DPIs) deposition and their fate in the respiratory system are influenced by a complex matrix of formulation, device, manufacturing and physiological variations. DPIs on the market have shown bioinequivalence between batches of the same product. Despite being clinically insignificant, they affect bioequivalence studies when a generic product is compared with the originator. This review discusses implications of batch-to-batch variability on bioequivalence study outcomes and shortcomings of current regulatory requirements. Possible formulation and manufacturing factors resulting in batch-to-batch variability highlight the inherent nature of this issue. Despite scholarly investigations and official regulatory guidance, there remains a need for reliable and realistic in vitro tests that accurately guide a representative reference product batch selection.

Prediction of pharmacokinetic parameters of inhaled indacaterol formulation in healthy volunteers using physiologically-based pharmacokinetic (PBPK) model

BACKGROUND

Inhaled formulations are the first choices for treating asthma and chronic obstructive pulmonary disease (COPD), attracting the increasing investment and development in the pharmaceutical industry. Both the equivalence of local and systemic exposures need to be considered when assessing the equivalence of generic inhaled drugs, which has become a dilemma in the development of generic inhaled drugs. There is an urgent need for reliable methods such as physiologically-based pharmacokinetic (PBPK) model to assist in the development of inhaled drugs.

METHOD

To test the strategy that in silico simulation is an effective tool in developing inhaled products and further assessing their clinically feasibility, a long-acting beta2-adrenergic agonists indacaterol, which was referred as the first-line therapy for patient with COPD, was selected as a tool drug. The PBPK model was established and the predicted plasma concentration curve was obtained by inputting the physicochemical properties of indacaterol and adjusting model parameters. The accuracy of simulation was verified by an alignment with the actual data. The main factor affecting PK in vivo was investigated by parameter sensitivity analysis. The biological equivalent size of indacaterol was investigated by virtual bioequivalence analysis.

RESULTS

The models of indacaterol after intravenous and oral administration were established and confirmed, and used as a background for PBPK model of inhaled administration. All those models showed favorable stability and applicability. Appropriate lung deposition was generated in the PBPK model, and the predicted plasma profile of indacaterol was consistent with the clinical actual observation values. Particle size is the most important factor affecting the PK of indacaterol in vivo. Furthermore, virtual bioequivalence simulation exhibited statistically comparable results between the particle size fluctuates in the range of 3.5-6.5 μm and baseline levels (D90 = 5 μm).

CONCLUSIONS

The PBPK model can simulate the pharmacokinetics and lung deposition of indacaterol, which will be a powerful tool to assist the development of inhaled drugs.

Determination of Passive Dry Powder Inhaler Aerodynamic Particle Size Distribution by Multi-Stage Cascade Impactor: International Pharmaceutical Aerosol Consortium on Regulation & Science (IPAC-RS) Recommendations to Support Both Product Quality Control and Clinical Programs

The multi-stage cascade impactor (CI) is the mainstay method for the determination of the aerodynamic particle size distribution (APSD) of aerosols emitted from orally inhaled products (OIPs). CIs are designed to operate at a constant flow rate throughout the measurement process. However, it is necessary to mimic an inhalation maneuver to disperse the powder into an aerosol when testing passive dry powder inhalers (DPIs), which constitute a significant portion of available products in this inhaler class. Methods in the pharmacopeial compendia intended for product quality assurance initiate sampling by applying a vacuum to the measurement apparatus using a timer-operated solenoid valve located downstream of the CI, resulting in a period when the flow rate through the impactor rapidly increases from zero towards the target flow rate. This article provides recommendations for achieving consistent APSD measurements, including selection of the CI, pre-separator, and flow control equipment, as well as reviewing considerations that relate to the shape of the flow rate-sampling time profile. Evidence from comparisons of different DPIs delivering the same active pharmaceutical ingredients (APIs) is indicative that the compendial method for APSD measurement is insensitive as a predictor of pharmacokinetic outcomes. Although inappropriate for product quality testing, guidance is therefore provided towards adopting a more clinically realistic methodology, including the use of an anatomically appropriate inlet and mimicking patient inhalation at the DPI while operating the CI at constant flow rate. Many of these recommendations are applicable to the testing of other OIP classes.

A new hypothesis to investigate bioequivalence of pharmaceutical inhalation products

BACKGROUND

This short communication reports a new hypothesis regarding bioequivalence of inhalation products which can potentially provide a reliable means to compare pharmaceutical aerosol formulations and inhalers.

METHODS

Available methods regarding the bioequivalence studies, inhaled drugs and advantages of exhaled breath condensate (EBC) samples were reviewed to develop this hypothesis.

RESULTS

It is postulated that two inhalation products providing the same drug concentrations in airway lining fluid (ALF) could be considered bioequivalent. The use of EBC tests which reflect ALF composition can be recommended as an alternative to current testing methods for consideration of bioequivalence.

CONCLUSION

The methods based on EBC analysis can potentially be applied to bioequivalence study of inhalation products and could reflect drug concentration in ALF. However, experimental studies would be necessary to support or refute this hypothesis on the novel application of EBC to bioequivalence in the future. Graphical abstract In vitro (cascade impactor) and In vivo (EBC concentration) corrolation for inhaled drugs.