Darragh Murnane

Direct ionization of solid-phase microextraction fibers for quantitative drug bioanalysis: from peripheral circulation to mass spectrometry detection.

A novel approach is described for the quantitative bioanalysis of drugs in blood samples by ionization of the analytes collected on solid-phase microextraction (SPME) fibers by mass spectrometry (MS). The technique combines the attractive features of SPME microsampling using minimal sample volumes with the speed, selectivity, and sensitivity capabilities of MS detection. The method reported in this study involved generating gas-phase ions directly from SPME fibers without the need for any additional sample preparation or chromatographic separation; the entire process was completed within 5 min. Traditionally, analytes extracted by SPME fibers are desorbed by washing with suitable solvents followed by a transfer into a sample vial and subsequent liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis to quantify the amount of analyte extracted and thereby determining the analyte concentration in the matrix. These sample preparation steps are completely eliminated by inserting the SPME fiber directly into the MS. Physiologically relevant concentrations of metoprolol and propranolol in blood samples were measured over several orders of magnitude down to concentration levels of 10 ng/mL. This preliminary assessment of direct SPME-MS showed high sensitivity (ng/mL), acceptable reproducibility (<30%), and lack of carryover. This novel approach simplifies current bioanalytical procedures providing time and cost savings. It demonstrates considerable potential for qualitative and quantitative pharmaceutical bioanalysis as well as other areas of challenging environmental and food analysis.

Rapid characterisation of the inherent dispersibility of respirable powders using dry dispersion laser diffraction

Graphical abstract

Nitrogen-14 Nuclear Quadrupole Resonance Spectroscopy: A Promising Analytical Methodology for Medicines Authentication and Counterfeit Antimalarial Analysis

We report the detection and analysis of a suspected counterfeit sample of the antimalarial medicine Metakelfin through developing nitrogen-14 nuclear quadrupole resonance ((14)N NQR) spectroscopy at a quantitative level. The sensitivity of quadrupolar parameters to the solid-state chemical environment of the molecule enables development of a technique capable of discrimination between the same pharmaceutical preparations made by different manufacturers. The (14)N NQR signal returned by a tablet (or tablets) from a Metakelfin batch suspected to be counterfeit was compared with that acquired from a tablet(s) from a known-to-be-genuine batch from the same named manufacturer. Metakelfin contains two active pharmaceutical ingredients, sulfalene and pyrimethamine, and NQR analysis revealed spectral differences for the sulfalene component indicative of differences in the processing history of the two batches. Furthermore, the NQR analysis provided quantitative information that the suspected counterfeit tablets contained only 43 ± 3%, as much sulfalene as the genuine Metakelfin tablets. Conversely, conventional nondestructive analysis by Fourier transform (FT)-Raman and FT-near infrared (NIR) spectroscopies only achieved differentiation between batches but no ascription. High performance liquid chromatography (HPLC)-UV analysis of the suspect tablets revealed a sulfalene content of 42 ± 2% of the labeled claim. The degree of agreement shows the promise of NQR as a means of the nondestructive identification and content-indicating first-stage analysis of counterfeit pharmaceuticals.

Dry Powder Formulations for Inhalation of Fluticasone Propionate and Salmeterol Xinafoate Microcrystals

Direct crystallization of active pharmaceutical ingredient (API) particles in the inhalable size range of 1-6 microm may overcome surface energization resulting from micronization. The aerosolization of fluticasone propionate (FP) and salmeterol xinafoate (SX) microcrystals produced by aqueous crystallization from poly(ethylene glycol) solutions was investigated using a twin stage impinger following blending with lactose. Fine particle fractions from SX formulations ranged from 15.98 +/- 2.20% from SX crystallized from PEG 6000 to 26.26 +/- 1.51% for SX crystallized from PEG 400. The FPF of microcrystal formulations increased as the particle size of microcrystals was increased. The aerosolization of SX from DPI blends was equivalent for the microcrystals and the micronized material. FP microcrystals, which had a needlelike morphology, produced similar FPFs (PEG 400: 17.15 +/- 0.68% and PEG 6000: 15.46 +/- 0.97%) to micronized FP (mFP; 14.21 +/- 0.54). The highest FPF (25.66 +/- 1.51%) resulted from the formulation of FP microcrystals with the largest median diameter (FP PEG 400B: 6.14 +/- 0.17 microm). Microcrystallization of SX and FP from PEG solvents offers the potential for improving control of particulate solid state properties and was shown to represent a viable alternative to micronization for the production of particles for inclusion in dry powder inhalation formulations.

Formulation pre-screening of inhalation powders using computational atom-atom systematic search method

The synthonic modeling approach provides a molecule-centered understanding of the surface properties of crystals. It has been applied extensively to understand crystallization processes. This study aimed to investigate the functional relevance of synthonic modeling to the formulation of inhalation powders by assessing cohesivity of three active pharmaceutical ingredients (APIs, fluticasone propionate (FP), budesonide (Bud), and salbutamol base (SB)) and the commonly used excipient, α-lactose monohydrate (LMH). It is found that FP (-11.5 kcal/mol) has a higher cohesive strength than Bud (-9.9 kcal/mol) or SB (-7.8 kcal/mol). The prediction correlated directly to cohesive strength measurements using laser diffraction, where the airflow pressure required for complete dispersion (CPP) was 3.5, 2.0, and 1.0 bar for FP, Bud, and SB, respectively. The highest cohesive strength was predicted for LMH (-15.9 kcal/mol), which did not correlate with the CPP value of 2.0 bar (i.e., ranking lower than FP). High FP-LMH adhesive forces (-11.7 kcal/mol) were predicted. However, aerosolization studies revealed that the FP-LMH blends consisted of agglomerated FP particles with a large median diameter (∼4-5 μm) that were not disrupted by LMH. Modeling of the crystal and surface chemistry of LMH identified high electrostatic and H-bond components of its cohesive energy due to the presence of water and hydroxyl groups in lactose, unlike the APIs. A direct comparison of the predicted and measured cohesive balance of LMH with APIs will require a more in-depth understanding of highly hydrogen-bonded systems with respect to the synthonic engineering modeling tool, as well as the influence of agglomerate structure on surface-surface contact geometry. Overall, this research has demonstrated the possible application and relevance of synthonic engineering tools for rapid pre-screening in drug formulation and design.

Dynamics of aerosol size during inhalation: Hygroscopic growth of commercial nebulizer formulations

The size of aerosol particles prior to, and during, inhalation influences the site of deposition within the lung. As such, a detailed understanding of the hygroscopic growth of an aerosol during inhalation is necessary to accurately model the deposited dose. In the first part of this study, it is demonstrated that the aerosol produced by a nebulizer, depending on the airflows rates, may experience a (predictable) wide range of relative humidity prior to inhalation and undergo dramatic changes in both size and solute concentration. A series of sensitive single aerosol analysis techniques are then used to make measurements of the relative humidity dependent thermodynamic equilibrium properties of aerosol generated from four common nebulizer formulations. Measurements are also reported of the kinetics of mass transport during the evaporation or condensation of water from the aerosol. Combined, these measurements allow accurate prediction of the temporal response of the aerosol size prior to and during inhalation. Specifically, we compare aerosol composed of pure saline (150 mM sodium chloride solution in ultrapure water) with two commercially available nebulizer products containing relatively low compound doses: Breath®, consisting of a simple salbutamol sulfate solution (5 mg/2.5 mL; 1.7 mM) in saline, and Flixotide® Nebules, consisting of a more complex stabilized fluticasone propionate suspension (0.25 mg/mL; 0.5 mM in saline. A mimic of the commercial product Tobi© (60 mg/mL tobramycin and 2.25 mg/mL NaCl, pH 5.5-6.5) is also studied, which was prepared in house. In all cases, the presence of the pharmaceutical was shown to have a profound effect on the magnitude, and in some cases the rate, of the mass flux of water to and from the aerosol as compared to saline. These findings provide physical chemical evidence supporting observations from human inhalation studies, and suggest that using the growth dynamics of a pure saline aerosol in a lung inhalation model to represent nebulizer formulations may not be representative of the actual behavior of the aerosolized drug solutions.

Investigations into the Formulation of Metered Dose Inhalers of Salmeterol Xinafoate and Fluticasone Propionate Microcrystals

PurposeTo investigate the aerosolization and behaviour of microparticles of salmeterol xinafoate (SX) and fluticasone propionate (FP) suspended in hydrofluoroalkane (HFA) propellant.MethodsMicrocrystals of SX and FP were produced from poly(ethylene glycol) by antisolvent crystallization. The suspension behaviour and aerosolization of the microcrystals when formulated as metered dose inhalers (MDIs) in HFA 134a propellant was compared with that of microparticles produced by micronization (mSX and mFP) using a glass twin stage impinger and by laser light diffraction using a pressurized cell.ResultsFP microparticles underwent non-reversible aggregation in suspension as seen by a doubling in the volume median diameter compared to the raw material. The degree of aggregation of SX particles in suspension was found to decrease as the particle size of the original particles increased. However, because the SX aggregate size was lowest for the particles with the smallest initial size (mSX), the highest fine particle fraction (FPF) of SX was obtained from a suspension of mSX. The FPFs following aerosolization of FP suspensions were similar although the FPF was lowest for particles with the largest original size.ConclusionsThe size of the aggregates in the HFA suspensions was found to correlate directly with the FPFs determined by impaction.

Formation and measurement of process induced disorder during the manufacture of inhalation medicines

The development and manufacture of inhalation medicines presents a number of complex challenges to the pharmaceutical scientist. Of paramount importance is delivering the drug particles with an optimal size for deposition in the desired regions of the lung. To achieve this, milling is typically applied to reduce the size of the drug particles destined for inhalation. Comminution has a number of important consequences for the physical properties of the processed drug particles. The generation of process induced disorder (PID) is a major issue which can lead to agglomeration of the powder and failure of the material to meet its specification. This review considers the challenges of achieving pulmonary delivery, the impact that particle size reduction during manufacture has on the properties of the inhaled drug particles and methods that may be employed to determine the extent of PID.

Optimizing the Entrainment Geometry of a Dry Powder Inhaler: Methodology and Preliminary Results

PurposeFor passive dry powder inhalers (DPIs) entrainment and emission of the aerosolized drug dose depends strongly on device geometry and the patient’s inhalation manoeuvre. We propose a computational method for optimizing the entrainment part of a DPI. The approach assumes that the pulmonary delivery location of aerosol can be determined by the timing of dose emission into the tidal airstream.MethodsAn optimization algorithm was used to iteratively perform computational fluid dynamic (CFD) simulations of the drug emission of a DPI. The algorithm seeks to improve performance by changing the device geometry. Objectives were to achieve drug emission that was: A) independent of inhalation manoeuvre; B) similar to a target profile. The simulations used complete inhalation flow-rate profiles generated dependent on the device resistance. The CFD solver was OpenFOAM with drug/air flow simulated by the Eulerian-Eulerian method.ResultsTo demonstrate the method, a 2D geometry was optimized for inhalation independence (comparing two breath profiles) and an early-bolus delivery. Entrainment was both shear-driven and gas-assisted. Optimization for a delay in the bolus delivery was not possible with the chosen geometry.ConclusionsComputational optimization of a DPI geometry for most similar drug delivery has been accomplished for an example entrainment geometry.

Pulmonary aerosol delivery and the importance of growth dynamics

Aerosols are dynamic systems, responding to variations in the surrounding environmental conditions by changing in size, composition and phase. Although, widely used in inhalation therapies, details of the processes occurring on aerosol generation and during inhalation have received little attention. Instead, research has focused on improvements to the formulation of the drug prior to aerosolization and the resulting clinical efficacy of the treatment. Here, we highlight the processes that occur during aerosol generation and inhalation, affecting aerosol disposition when deposited and, potentially, impacting total and regional doses. In particular, we examine the response of aerosol particles to the humid environment of the respiratory tract, considering both the capacity of particles to grow by absorbing moisture and the timescale for condensation to occur.