Simultaneous and trace-level quantification of four benzene sulfonate potential genotoxic impurities in doxofylline active pharmaceutical ingredients and tablets using high-performance liquid chromatography with ultraviolet detection

In the production of doxofylline, the common occurrence of toxic p-toluene sulfonate generation prompted the development and validation of a method using HPLC with ultraviolet detection (HPLC-UV). This method is designed for detecting four potential genotoxic impurities (PGIs) present in both doxofylline drug substance and tablets, with a focus on the UV-absorbing group p-toluene sulfonate. The four impurities were methyl 4-methylbenzenesulfonate (PGI-1), ethyl 4-methylbenzenesulfonate (PGI-2), 2-hydroxyethyl 4-methylbenzenesulfonate (PGI-3), and 2-(4-methylphenyl)sulfonyloxyethyl 4-methylbenzenesulfonate (PGI-4). In this method, chromatographic separation was achieved using a Waters Symmetry C18 column (250 mm × 4.6 mm, 5 μm). The mobile phases consisted of 20% acetonitrile as mobile phase A and pure acetonitrile as mobile phase B, operating in gradient elution mode at a flow rate of 1.0 mL/min. According to the guidelines of the International Conference on Harmonization, it was determined that this method could quantify four PGIs at 0.0225 μg/mL in samples containing 60 mg/mL. The validated approach demonstrated excellent linearity (R2 > 0.999) across the concentration range of 30%-200% (relative to 0.075 μg/mL doxofylline) for the four PGIs. The accuracy of this method for the four PGIs ranged from 94.8% to 100.4%. The reverse-phase-HPLC-UV analytical method developed in this study is characterized by its speed and precision, making it suitable for the sensitive analysis of benzene sulfonate PGIs in doxofylline drug substances and tablets.

Effects of doxofylline as an adjuvant on severe exacerbation and long-term prognosis for COPD with different clinical subtypes

OBJECTIVE

This study aimed to investigate the effectiveness of doxofylline as an adjuvant in reducing severe exacerbation for different clinical subtypes of chronic obstructive pulmonary disease (COPD).

METHODS

The clinical trial was an open-label non-randomized clinical trial that enrolled patients with COPD. The patients were divided into two groups (doxofylline group[DG] and non-doxofylline group[NDG]) according to whether the adjuvant was used. Based on the proportion of inflammatory cells present, the patients were divided into neutrophilic, eosinophilic, and mixed granulocytic subtypes. The rates of severe acute exacerbation, use of glucocorticoids, and clinical symptoms were followed up in the first month, the third month, and the sixth month after discharge.

RESULTS

A total of 155 participants were included in the study. The average age of the participants was 71.2  ±  10.1 years, 52.3% of the patients were male, and 29.7% of the participants had extremely severe cases of COPD. In the third month after discharge the numbers of patients exhibiting severe exacerbation among the neutrophilic subtype were 5 (6.6%) in the DG versus 17 (22.4%) in the NDG (incidence rate ratio[IRR] = 0.4 [95% CI: 0.2-0.9] P = 0.024). In the sixth month after discharge, the numbers were 3 (3.9%) versus 13 (17.1%; IRR = 0.3 [95%; CI: 0.1-0.9], P = 0.045), and those for the eosinophilic subtype were 0 (0.0%) versus 4 (14.8%), P = 0.02. In the eosinophilic subtype, the results for forced expiratory volume in the first second and maximal mid-expiratory flow were significantly higher in the DG. The mean neutrophil and eosinophil levels were significantly lower than in the NDG among the neutrophilic subtype, and the neutrophil percentage was lower than in the NDG among the eosinophilic subtype. At the six-month follow-up, the dose adjustment rates of the neutrophilic and eosinophilic subtypes showed a significant difference (P< 0.05).

CONCLUSIONS

As an adjuvant drug, doxofylline has a good therapeutic effect on patients with the neutrophilic and eosinophilic clinical subtypes of COPD. It can reduce the incidence of severe exacerbation, the use of glucocorticoids, and inflammatory reactions in the long term (when used for a minimum of 3 months).

Studying the Mechanism of Interaction of Doxofylline with Human Lysozyme: A Biophysical and In Silico Approach

In this study, multiple spectroscopic and computational methods were utilized to investigate the binding mechanism of doxofylline with lysozyme. The in vitro methods were used to obtain the binding kinetics and thermodynamics. UV-vis spectroscopy indicated the formation of complex between doxofylline and lysozyme. The Gibb's free energy and binding constant from UV-vis data was obtained as -7.20 kcal M^-1 and 1.929 × 10⁵ M^-1, respectively. Doxofylline successfully quenched the fluorescence of lysozyme, confirming the formation of complex. The k_q and K_sv values for the quenching of lysozyme's fluorescence by doxofylline were 5.74 × 10¹¹ M^-1 s^-1 and 3.32 × 10³ M^-1, respectively. These values signified a moderate binding affinity between doxofylline and lysozyme. In synchronous spectroscopy, red shifts were observed for indicating the changes in microenvironment of lysozyme following the binding of doxofylline. The secondary structural analysis was determined using circular dichroism (CD) which revealed an increase in % α-helical as a result of doxofylline interaction. The binding affinity and flexibility of lysozyme upon complexation have been revealed via molecular docking and molecular dynamic (MD) simulations, respectively. According to the many parameters of the MD simulation, the lysozyme-doxofylline complex was stable under physiological conditions. All during the simulation time, hydrogen bonds were continuously present. The MM-PBSA binding energy for lysozyme and doxofylline binding was found to be -30.55 kcal mol^-1.

Pediatric Asthma: New Role for an Old Drug

The panoply of anti-asthma drugs for children between 6 and 18 years is not limited to those reported in the guidelines. In this review, we will re-assess the role of doxofylline, a xanthine characterized by a much higher handling than that of theophylline, as add-on treatment in pediatric asthma grade 1-4. Ten studies evaluated doxofylline in the treatment of asthma of patients non-responsive to the first-line inhaled corticosteroids. Of these, two included children and one was exclusively pediatric. According to their results, doxofylline exerts a powerful bronchodilator and anti-inflammatory activity, which can be exploited when the inhaled oral corticosteroids are not sufficient to get the desired effect of reducing symptoms. Unlike theophylline, doxofylline does not require blood testing. It can be administered together with or as an alternative to a series of other drugs considered in additional therapy.

Doxofylline Protects Gram-Negative Pathogens against Antibiotic-Mediated Killing

Given the growing rate of Gram-negative bacterial infections, antibiotics are now frequently prescribed for various respiratory diseases. Doxofylline is a newer generation xanthine with both bronchodilating and anti-inflammatory activities, but its influence on antibiotics remains poorly understood. Here, we first report the discovery of doxofylline-induced high minimum inhibitory concentrations of antibiotics. We also showed that doxofylline blocked antimicrobial-mediated killing for Gram-negative pathogens in vitro and in murine lung infection models in vivo. By combining efflux pump inhibition tests, gene expression analyses, and using the gene tolC knockout strain, we found that doxofylline positively regulated gene expression of the AcrAB-TolC efflux pump and attenuated the effect of doxofylline on antibacterial activities in ΔtolC mutants. Notably, doxofylline-mediated protection correlated with decreased reactive oxygen species (ROS) production. Collectively, our study indicates that doxofylline protects Gram-negative bacteria from antimicrobial lethality by regulating the AcrAB-TolC efflux pump in a TolC-dependent manner and suppressing antibiotic-induced ROS accumulation. These results suggest caution when using antibiotics alongside doxofylline in clinical treatment.

Effect of terbutaline plus doxofylline on chronic obstructive pulmonary disease

OBJECTIVES

This study focused on patients with chronic obstructive pulmonary disease (COPD) and aimed at investigating the effect of terbutaline plus doxofylline on their pulmonary function and quality of life.

METHODS

Ninety COPD patients were divided by using a random number table into a control group (administration of doxofylline) and experimental group (administration of terbutaline combined with doxofylline), with 45 patients in each group. The therapeutic efficacy, pre- and post-treatment pulmonary function and the quality of life were compared between the control and experimental groups.

RESULTS

After treatment, patients in the experimental group had lower levels of interleukin-8, tumor necrosis factor α and C-reactive protein (all P<0.001), higher forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), and FEVl/FVC (all P<0.001), and lower total score of COPD assessment test (P<0.05) compared with the control group.

CONCLUSION

Terbutaline combined with doxofylline for the treatment of COPD patients can efficiently decrease inflammatory factor levels, and bring them better pulmonary function and quality of life.

Doxofylline is not just another theophylline!

Doxofylline, which differs from theophylline in containing the dioxalane group at position 7, has comparable efficacy to theophylline in the treatment of respiratory diseases, but with an improved tolerability profile and a favorable risk-to-benefit ratio. Furthermore, it does not have significant drug-drug interactions as exhibited with theophylline, which make using theophylline more challenging, especially in elderly patients with co-morbidities receiving multiple classes of drug. It is now clear that doxofylline also possesses a distinct pharmacological profile from theophylline (no significant effect on any of the known phosphodiesterase isoforms, no significant adenosine receptor antagonism, no direct effect on histone deacetylases, interaction with β₂-adrenoceptors) and therefore, should not be considered as just a modified theophylline. Randomized clinical trials of doxofylline to investigate the use of this drug to reduce exacerbations and hospitalizations due to asthma or COPD as an alternative to expensive biologics, and certainly as an alternative to theophylline are to be encouraged.

Assessment of various second-line medications in addition to inhaled corticosteroid in asthma patients: a randomized controlled trial

Many patients with persistent asthma cannot achieve the treatment goal for asthma with a single controller medication. The aim of the present study was to assess lung function and rescue medication use in asthma patients receiving four different categories of drugs in combination with an inhaled corticosteroid. Patients recruited to the study were randomized into four groups to receive budesonide with either formoterol, doxofylline, montelukast or tiotropium for a period of 3 months. Lung function (i.e. forced expiratory volume in 1 s (FEV1 )) and rescue medication use were determined at baseline and on Day 15, 30, 45, 60 and 90 of treatment. A total of 297 patients completed the study. At baseline, no significant differences (P > 0.05) were observed in any of the outcome measures. Significant within-group improvement in FEV1 was observed in all groups. On Day 90, between-group differences showed that the improvement in FEV1 was significantly (P < 0.05) higher for patients receiving budesonide + formoterol, followed by budesonide + montelukast and budesonide + doxofylline, and least for those receiving budesonide + tiotropium. Similarly, within- and between-group comparisons showed significant (P < 0.05) reductions in rescue medication use in all groups. However, the magnitude of the decrease was greater in the budesonide + formoterol group, followed by the budesonide + montelukast, budesonide + doxofylline and budesonide + tiotropium groups. Based on our findings, among the second-line treatment regimens, budesonide with either montelukast or doxofylline was found to be better than budesonide + tiotropium in patients with mild-to-moderate persistent asthma. Further studies with a longer duration are likely to be useful.

Assessment of montelukast, doxofylline, and tiotropium with budesonide for the treatment of asthma: which is the best among the second-line treatment? A randomized trial

PURPOSE

Data comparing various second-line treatments for asthma with subjective and objective assessment are lacking. This study aimed to compare the efficacy and safety of montelukast, doxofylline, and tiotropium with a low-dose budesonide in patients with mild to moderate persistent asthma.

METHODS

Patients, all of whom were concurrently using inhaled budesonide (400 µg), were treated for 6 months with formoterol (12 µg), montelukast (10 mg), doxofylline (400 mg), or tiotropium (18 µg). Outcomes included forced expiratory volume in 1 second (FEV1), Saint George Respiratory Questionnaire (SGRQ) scores, asthma symptom scores (daytime and nighttime), and assessment of tolerability and rescue medication use.

FINDINGS

A total of 297 patients completed the study. In all 4 groups, significant improvements were observed in all the outcome measures, with formoterol treatment having greater and earlier improvements than the other 3 second-line controller medications with budesonide. Among the second-line treatments, monteradlukast improved the FEV1 from day 45 (P < 0.01), SGRQ scores from day 30 (P < 0.0001), daytime scores from day 30 (P < 0.05), nighttime scores from day 30 (P < 0.0001), and rescue medication use from day 15 (P < .0001) at a faster rate than doxofylline or tiotropium with budesonide. No patients discontinued the treatment because of adverse reactions.

IMPLICATIONS

Among the tested second-line treatment regimens, the budesonide/montelukast combination was found to be superior to either the budesonide/doxofylline or budesonide/tiotropium combination in all the outcome measures without adversely affecting the tolerability of the patients. Further clinical studies with blinding techniques are likely to be useful.

Pulmonary function assessment in mild to moderate persistent asthma patients receiving montelukast, doxofylline, and tiotropium with budesonide: a randomized controlled study

BACKGROUND

There is no comparative study among asthma patients receiving first-line versus various second-line treatment regimens for mild to moderate persistent asthma.

OBJECTIVE

We assessed the pulmonary function in asthma patients receiving montelukast, doxofylline, and tiotropium with budesonide in a pilot group.

METHODS

Patients were recruited as per the study criteria and randomly allocated to 4 groups to receive budesonide (400 µg) with formoterol (12 µg), doxofylline (400 mg), montelukast (10 mg), or tiotropium (18 µg) for a period of 3 months. Outcomes included forced expiratory volume in 1 second (FEV1) and rescue medication use.

RESULTS

A total of 167 patients were recruited; among them, 123 patients completed the study. At baseline, no significant difference (P > 0.05) was observed in any of the outcome measures. Significant within-group improvement in FEV1 was observed in all the groups. At day 90, between-group difference revealed that improvement in FEV1 was significantly (P < 0.05) high for budesonide plus formoterol followed by budesonide plus doxofylline, budesonide plus montelukast, and, lastly, budesonide plus tiotropium. Similarly, within-group comparison revealed a significant (P < 0.05) reduction in rescue medication use in all the groups. The intensity in decrease was more in budesonide plus formoterol group followed by budesonide plus doxofylline, budesonide plus montelukast, and budesonide plus tiotropium groups.

CONCLUSION

On the basis of our findings, among the second-line treatment regimens, budesonide plus doxofylline and budesonide plus montelukast was found to be better than budesonide plus tiotropium in patients with mild to moderate persistent asthma. Further studies with a larger sample size are likely to be useful.