A simplified procedure for the analysis of formoterol in human urine by liquid chromatography–electrospray tandem mass spectrometry: Application to the characterization of the metabolic profile and stability of formoterol in urine

Pharmacokinetic considerations surrounding triple therapy for uncontrolled asthma

INTRODUCTION

Solid pharmacological rationale and clinical evidence support the use of a combination of an inhaled corticosteroid (ICS), a long-acting β2-agonist, and a long-acting muscarinic antagonist in severe asthma, which clinically results in increased lung function, improved symptoms, and decreased exacerbation rates.

AREAS COVERED

We examined the pharmacokinetic issues associated with triple therapy for uncontrolled asthma. We considered the pharmacokinetic characteristics of the three drug classes, the role of inhalers in influencing their pharmacokinetic behavior, and the impact of severe asthma on the pharmacokinetics of inhaled drugs.

EXPERT OPINION

The pharmacokinetics of ICSs and bronchodilators are not affected to a great extent by severe asthma, according to a detailed review of the currently accessible literature. Compared to healthy people, patients with severe asthma show only minor variations in a few pharmacokinetic characteristics, which are unlikely to have therapeutic significance and do not require particular attention. However, the difficulty of obtaining pharmacokinetic profiles of the three drugs included in a triple therapy suggests that the clinical response should be followed over time, which can be considered a good surrogate indicator of whether the drugs have reached sufficient concentrations in the lung to exert a valid pharmacological action.

Electro-oxidation of formoterol fumarate on the surface of novel poly(thiazole yellow-G) layered multi-walled carbon nanotube paste electrode

The current study explicates the electro-oxidation behavior of formoterol fumarate (FLFT) in the presence of uric acid (UA) on the surface of poly thiazole yellow-G (TY-G) layered multi-walled carbon nanotube paste electrode (MWCNTPE). The modified (Poly(TY-G)LMWCNTPE) and unmodified (MWCNTPE) electrode materials were characterized through electrochemical impedance spectroscopy (EIS), field emission scanning electron microscopy (FE-SEM), and cyclic voltammetry (CV) approaches. The characterization data confirms the good conducting and electrocatalytic nature with more electrochemical active sites on the Poly(TY-G)LMWCNTPE than MWCNTPE towards the FLFT analysis in the presence of UA. Poly(TY-G)LMWCNTPE easily separates the two drugs (FLFT and UA) even though they both have nearer oxidation peak potential. The electro-catalytic activity of the developed electrode is fast and clear for FLFT electro-oxidation in 0.2 M phosphate buffer (PB) of pH 6.5. The Poly(TY-G)LMWCNTPE offered a well-resolved peak with the highest electro-oxidation peak current at the peak potential of 0.538 V than MWCNTPE. The potential scan rate and oxidation peak growth time studies show the electrode reaction towards FLFT electro-oxidation is continued through a diffusion-controlled step. The variation of concentration of FLFT in the range from 0.2 to 1.5 µM (absence of UA) and 3.0 to 8.0 μM (presence of UA) provides a good linear relationship with increased peak current and a lower limit of detection (LOD) values of 0.0128 µM and 0.0129 µM, respectively. The prepared electrode gives a fine recovery for the detection of FLFT in the medicinal sample with acceptable repeatability, stability, and reproducibility.

Enantioselective disposition of (R,R)-formoterol, (S,S)-formoterol and their respective glucuronides in urine following single inhaled dosing and application to doping control

Formoterol is a long-acting beta2-adrenoceptor agonist (LABA) used for the treatment of asthma and exercise-induced bronchoconstriction. Formoterol is usually administered as a racemic (rac-) mixture of (R,R)- and (S,S)-enantiomers. While formoterol is restricted by the World Anti-Doping Agency (WADA), inhalation of formoterol is permitted to a predetermined dose (54 μg/24 hours) and a urine threshold of 40 ng/mL. However, chiral switch enantiopure (R,R)-formoterol is available, effectively doubling the therapeutic advantage for the same threshold. The aim of this study was to investigate whether formoterol exhibits enantioselective urinary pharmacokinetics following inhalation. Six healthy volunteers were administered a 12 μg inhaled dose of rac-formoterol. Urine was collected over 24 hours and analyzed by enantioselective ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) assay. Total (free drug plus conjugated metabolite) median (min-max) rac-formoterol urine levels following inhalation were 1.96 (1.05-13.4) ng/mL, 1.67 (0.16-9.67) ng/mL, 0.45 (0.16-1.51) ng/mL, 0.61 (0.33-0.78) ng/mL, and 0.17 (0.08-1.06) ng/mL at 2, 4, 8, 12, and 24 hours, respectively, well below the 2019 urine threshold. The proportion of conjugation differed between enantiomers with glucuronide conjugation much greater for (R,R)-formoterol (around 30%-60% of total) compared to (S,S)-formoterol (0%-30%). There was clear evidence of inter-individual enantioselectivity observed in the ratios of (R,R):(S,S)-formoterol, where (S,S)- was predominant in free formoterol, and (R,R)- predominant in the conjugated metabolite. In conclusion, rac-formoterol delivered by inhalation exhibits enantioselective elimination in urine following single-dose administration. Enantioselective assays should be employed in doping control to screen for banned beta2-agonist chiral switch products such as (R,R)-formoterol, and total hydrolyzed rac-formoterol is warranted to account for inter-individual differences in enantioselective glucuronidation.

Development of a multi-functional concurrent assay using weak cation-exchange solid-phase extraction (WCX-SPE) and reconstitution with a diluted sample aliquot for anti-doping analysis

RATIONALE

In addition to the development of adequate screening methods for multiple compounds, the World Anti-Doping Agency (WADA) requires anti-doping laboratories to analyze prohibited substances and their metabolites from various classes. This task presents a difficult challenge for all agencies and interests involved in the field of doping control.

METHODS

A screening method is reported in which hybrid sample preparation was performed using a combination of weak cation-exchange solid-phase extraction (WCX-SPE) and the 'Dilute and Shoot' strategy in order to take advantage of both the methodologies. Target substances were extracted using a WCX cartridge and reconstituted with a diluted sample aliquot that included 20% of an untreated urine sample. The target substances were further analyzed by high-performance liquid chromatography/triple quadrupole mass spectrometry (LC/MS).

RESULTS

The SPE procedure was optimized using a cartridge-washing step, elution conditions, and elution volume. The cartridge-washing step, which was performed using 10% methanol, improved the overall recovery of target substances. Since the recovery was observed to vary according to the pH of the eluting solution, we applied an elution step using both an acid and a basic organic solvent to achieve complementary recovery. Reconstitution of the diluted aliquot sample was performed to recover the polar substances.

CONCLUSIONS

The method was validated and applied to real samples in accordance with the external quality assessment scheme of WADA and to the previously reported samples that had provided positive test results. This novel method using hybrid sample preparation and LC/MS could be useful to screen multiple classes of the 264 targeted substances in anti-doping analysis.

Beta2-Agonist Doping Control and Optical Isomer Challenges

The World Anti-Doping Agency (WADA) currently allows therapeutic use of the beta2-agonists salbutamol, formoterol and salmeterol when delivered via inhalation despite some evidence suggesting these anti-asthma drugs may be performance enhancing. Beta2-agonists are usually administered as 50:50 racemic mixtures of two enantiomers (non-superimposable mirror images), one of which demonstrates significant beta2-adrenoceptor-mediated bronchodilation while the other appears to have little or no pharmacological activity. For salbutamol and formoterol, urine thresholds have been adopted to limit supratherapeutic dosing and to discriminate between inhaled (permitted) and oral (prohibited) use. However, chiral switches have led to the availability of enantiopure (active enantiomer only) preparations of salbutamol and formoterol, which effectively doubles their urine thresholds and provides a means for athletes to take supratherapeutic doses for doping purposes. Given the availability of these enantiopure beta2-agonists, the analysis of these drugs using enantioselective assays should now become routine. For salmeterol, there is currently only a therapeutic dose threshold and adoption of a urinary threshold should be a high priority for doping control.

Development and validation of an UHPLC-MS/MS method for β2-agonists quantification in human urine and application to clinical samples

A fast analytical method for the simultaneous detection of 24 β₂-agonists in human urine was developed and validated. The method covers the therapeutic drugs most commonly administered, but also potentially abused β₂-agonists. The procedure is based on enzymatic deconjugation with β-glucuronidase followed by SPE clean up using mixed-phase cartridges with both ion-exchange and lipophilic properties. Instrumental analysis conducted by UHPLC-MS/MS allowed high peak resolution and rapid chromatographic separation, with reduced time and costs. The method was fully validated according ISO 17025:2005 principles. The following parameters were determined for each analyte: specificity, selectivity, linearity, limit of detection, limit of quantification, precision, accuracy, matrix effect, recovery and carry-over. The method was tested on real samples obtained from patients subjected to clinical treatment under chronic or acute therapy with either formoterol, indacaterol, salbutamol, or salmeterol. The drugs were administered using pressurized metered dose inhalers. All β₂-agonists administered to the patients were detected in the real samples. The method proved adequate to accurately measure the concentration of these analytes in the real samples. The observed analytical data are discussed with reference to the administered dose and the duration of the therapy.

Applications and challenges in using LC–MS/MS assays for quantitative doping analysis

LC–MS/MS is useful for qualitative and quantitative analysis of ‘doped’ biological samples from athletes. LC–MS/MS-based assays at low-mass resolution allow fast and sensitive screening and quantification of targeted analytes that are based on preselected diagnostic precursor–product ion pairs. Whereas LC coupled with high-resolution/high-accuracy MS can be used for identification and quantification, both have advantages and challenges for routine analysis. Here, we review the literature regarding various quantification methods for measuring prohibited substances in athletes as they pertain to World Anti-Doping Agency regulations.

Bioanalytical techniques in discrimination between therapeutic and abusive use of drugs in sport

The discrimination between therapeutic and abusive use of drugs in sports is performed using threshold concentrations or reporting levels, and the detection of the substances in a sample is only reported as an adverse analytical finding when the concentration exceeds the threshold or the reporting level. In this paper, the strategies of discrimination and the analytical methods used for the main groups of substances where the distinction is needed (β-2 agonists, ephedrines, glucocorticoids and morphine) will be reviewed. Nowadays, LC–MS is the method of choice for the analysis of these substances and, in most of the cases, a simple dilution of the urine sample is performed before the chromatographic analysis.

Preparation of yolk-shell structured copper oxide@silica oxide spheres and their application in high performance electrochemical sensing of Formoterol fumarate residues in swine feed and tissues

In this paper, we report a facile route to synthesize yolk-shell structured copper oxide@silica oxide (CuO@SiO2) spheres and their application to construct an electrochemical Formoterol fumarate (FF) sensor. The CuO@SiO2 was characterized by means of Fourier transform infrared spectroscopy, X-ray powder diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. Further, FF was electrocatalytically oxidized at the CuO@SiO2 film modified glassy carbon electrode (GCE), which led to a sensitive determination of FF. The oxidation current of FF was linear with concentration in the range of 0.030-10 μM and the detection limit was found to be 5.0 nM (S/N = 3). The observed analytical parameters such as wide linear range, low detection limit and short response time were superior to previously reported FF sensors. Finally, it was demonstrated that the proposed sensor could be used for the selective determination of FF present in swine feed and tissues.