Clinically Relevant In Vitro Testing of Orally Inhaled Products-Bridging the Gap Between the Lab and the Patient

Current pharmacopeial methods for in vitro orally inhaled product (OIP) performance testing were developed primarily to support requirements for drug product registration and quality control. In addition, separate clinical studies are undertaken in order to quantify safety and efficacy in the hands of the patient. However, both laboratory and clinical studies are time-consuming and expensive and generally do not investigate either the effects of misuse or the severity of the respiratory disease being treated. The following modifications to laboratory evaluation methodologies can be incorporated without difficulty to provide a better linkage from in vitro testing to clinical reality: (1) examine all types of OIP with patient-representative breathing profiles which represent normal inhaler operation in accordance with the instructions for use (IFU); (2) evaluate OIP misuse, prioritizing the importance of such testing on the basis of (a) probability of occurrence and (b) consequential impact in terms of drug delivery in accordance with the label claim; and (3) use age-appropriate patient-simulated face and upper airway models for the evaluation of OIPs with a facemask. Although it is not necessarily foreseen that these suggestions would form part of future routine quality control testing of inhalers, they should provide a closer approximation to the clinical setting and therefore be useful in the preparation for in vivo studies and in improving guidance for correct use.

Extra-fine particle inhaled corticosteroids, pharma-cokinetics and systemic activity in children with asthma

During recent years, extra-fine particle inhaled corticosteroids with a median aerodynamic diameter ≤2 μm have been introduced in the treatment of asthma. The aim of this paper was to review pharmacokinetics and systemic activity of extra-fine particle hydroalkane pressurized metered dose inhaled (pMDI) ciclesonide and beclomethasone dipropionate in children. A literature review was performed. Systemic bioavailability of oral and pulmonary deposition of extra-fine ciclesonide and beclomethasone dipropionate was 52% and 82%, the half-life in serum 3.2 and 1.5 h and first-pass hepatic metabolism >99% and 60%, respectively. Secondary analyses of urine cortisol/creatinine excretion found no effects of ciclesonide pMDI between 40 and 320 μg/day or of beclomethasone dipropionate pMDI between 80 and 400 μg/day. Ciclesonide pMDI 40, 80 and 160 μg/day caused no effects on short-term lower leg growth rate as assessed by knemometry. Ciclesonide 320 μg/day was associated with a numerically short-term growth suppression equivalent to 30% which was similar to 25% and 36% suppression caused by beclomethasone dipropionate HFA and CFC 200 μg/day, respectively. Consistent with the differences in key pharmacokinetic features, beclomethasone dipropionate is associated with a systemic activity detected by knemometry at a lower dose than ciclesonide. Whether that correlates with a clinically important difference remains to be explored. Assessments of systemic activity of beclomethasone dipropionate <200 μg/day and of ciclesonide >180 μg/day as well as head-to-head comparisons are warranted. Preferably, such studies should apply the sensitive method of knemometry.

Developing ways to evaluate in the laboratory how inhalation devices will be used by patients and care-givers: the need for clinically appropriate testing

The design of methods in the pharmaceutical compendia for the laboratory-based evaluation of orally inhaled product (OIP) performance is intentionally aimed for simplicity and robustness in order to achieve the high degree of accuracy and precision required for the assurance of product quality in a regulated environment. Consequently, performance of the inhaler when used or even misused by the patient or care-giver has often not been assessed. Indeed, patient-use-based methodology has been developed in a somewhat piecemeal basis when a need has been perceived by the developing organization. There is, therefore, a lack of in-use test standardization across OIP platforms, and often important details have remained undisclosed beyond the sponsoring organization. The advent of international standards, such as ISO 20072:2009, that focus specifically on the OIP development process, together with the need to make these drug delivery devices more patient-friendly as an aid to improving compliance, is necessitating that clinically appropriate test procedures be standardized at the OIP class level. It is also important that their capabilities and limitations are well understood by stakeholders involved in the process. This article outlines how this process might take place, drawing on current examples in which significant advances in methodology have been achieved. Ideally, it is hoped that such procedures, once appropriately validated, might eventually become incorporated into the pharmacopeial literature as a resource for future inhaler developers, regulatory agencies, and clinicians seeking to understand how these devices will perform in use to augment ongoing product quality testing which is adequately served by existing methods.

Considerations for Designing In Vitro Bioequivalence (IVBE) Studies for Pressurized Metered Dose Inhalers (pMDIs) with Spacer or Valved Holding Chamber (S/VHC) Add-on Devices

BACKGROUND

The choice of analytical test methods and associated statistical considerations are considered for the laboratory testing of pressurized metered dose inhaler-spacer/valved holding chamber (pMDI-S/VHC) combinations for in vitro bioequivalence (IVBE).

METHODS

Four scenarios are presented for comparing TEST ("second entry" or "generic") versus REF ("innovator"): (1) innovator and second entry product pMDI alone without any S/VHC (baseline comparison); (2) innovator and second entry pMDI product with the same S/VHC; (3) innovator pMDI product with existing S/VHC and second entry product with a different S/VHC; and (4) introduction of a second, different S/VHC to be used with a given innovator pMDI product. The following aspects should be reviewed in the preparatory stage of designing experiments to establish IVBE: (a) the inclusion of delayed inhalation; (b) the utilization of age-appropriate flow rates; and (c) the use of anatomically appropriate face models for evaluation of devices with a facemask. Statistical considerations that fit in with such experimental methods include: selection of pMDI batches and S/VHC lots; choice of sample size and acceptance criteria; bracketing or worst case approaches; and balanced/paired designs. A stepwise approach for selection of impactor stage groupings is presented, and an approach to determine realistic acceptance criteria based on REF product characteristics is suggested.

RESULTS

An example of an efficient statistical design of experiment is provided for each scenario, together with alternate approaches for calculation of confidence intervals for the mean TEST/REF relationship. It is important to appreciate that the optimal design depends on balancing numerous considerations and will thus likely differ from case to case; hence, the designs presented here should be seen as illustrations rather than the only option available. More effective approaches may be found that suit a particular case at hand.

CONCLUSIONS

The information provided will assist in developing correlations in support of IVBE for these add-on devices.