Doxofylline: a new generation xanthine bronchodilator devoid of major cardiovascular adverse effects

Theophylline Acetaldehyde as the Initial Product in Doxophylline Metabolism in Human Liver

Doxophylline (DOXO) and theophylline are widely used as bronchodilators for treating asthma and chronic obstructive pulmonary disease, and DOXO has a better safety profile than theophylline. How DOXO's metabolism and disposition affect its antiasthmatic efficacy and safety remains to be explored. In this study, the metabolites of DOXO were characterized. A total of nine metabolites of DOXO were identified in vitro using liver microsomes from human and four other animal species. Among them, six metabolites were reported for the first time. The top three metabolites were theophylline acetaldehyde (M1), theophylline-7-acetic acid (M2), and etophylline (M4). A comparative analysis of DOXO metabolism in human using liver microsomes, S9 fraction, and plasma samples demonstrated the following: 1) The metabolism of DOXO began with a cytochrome P450 (P450)-mediated, rate-limiting step at the C ring and produced M1, the most abundant metabolite in human liver microsomes. However, in human plasma, the M1 production was rather low. 2) M1 was further converted to M2 and M4, the end products of DOXO metabolism in vivo, by non-P450 dismutase in the cytosol. This dismutation process also relied on the ratio of NADP⁺/NADPH in the cell. These findings for the first time elucidated the metabolic sites and routes of DOXO metabolism in human. SIGNIFICANCE STATEMENT: We systematically characterized doxophylline metabolism using in vitro and in vivo assays. Our findings evolved the understandings of metabolic sites and pathways for methylxanthine derivatives with the aldehyde functional group.

A Sensitive Microscale HPLC-UV Method for the Determination of Doxofylline and its Metabolites in Plasma: An Adapted Method for Therapeutic Drug Monitoring in Children

Background:

Doxofylline (DXE) is a novel methylxanthine derivative used in the treatment of asthma and Chronic Obstructive Pulmonary Diseases (COPD). Therapeutic Drug Monitoring (TDM) has been proposed in adults, while the adapted analytical method and TDM data are still missing in children.

Methods:

A highly sensitive and stability indicating High-Performance Liquid Chromatography (HPLC) method of DXE with caffeine as the internal standard, was developed and validated by separating its metabolites, β-Hydroxyethyltheophylline (HPE) and Theophylline (TPE). HPLC separation is achieved on C18 column connected to an ultraviolet detector (276 nm), using acetonitrile and ultra-pure water in a gradient mode of elution at a flow rate of 0.9 mL/min at 25°C. A liquid-liquid extraction method using ethyl acetate was developed with a small sample volume of plasma of 50 μL. Trough concentration was monitored in children receiving DXE therapy.

Results:

The method was linear over the concentration ranges from 0.4-20 µg/mL for DXE, HPE and TPE, respectively, in plasma. The limits of quantification were 0.4 µg/mL. Intra- and interday coefficients of variation did not exceed 6.5%, and the accuracy ranged from 94.9% to 112.5%. A total of 39 children (mean age of 1.8 years, range: 0.3-5.7 years) were included. The pediatric patients had detectable DXE concentrations with a mean value of 1.78 µg/mL (range from 0.49 to 6.36 µg/mL), and HPE measurable concentrations with a mean value of 0.52 µg/mL (range from 0.40 to 0.82 µg/mL), while the TPE could not be measured in any patient.

Conclusion:

A sensitive, reliable, and adapted HPLC method has been developed for the simultaneous analysis of DXE and its metabolites in children. The DXE and its metabolites trough concentrations showed large inter-individual variability.

Xanthine scaffold: scope and potential in drug development

Medicinal plants have been the basis for discovery of various important marketed drugs. Xanthine is one such lead molecule. Xanthines in various forms (caffeine, theophylline, theobromine, etc) are abode in tea, coffee, cocoa, chocolate etc. giving them popular recognition. These compounds are best known for their diverse pharmaceutical applications as cyclic nucleotide phosphodiesterase inhibition, antagonization of adenosine receptor, anti-inflammatory, anti-microbial, anti-oxidant and anti-tumor activities. These properties incentivize to use xanthine as scaffold to develop new derivatives. Chemical synthesis contributes greater diversity in xanthine based derivatisation. With highlighting the existing challenges in chemical synthesis, the present review focuses the probable solution to fill existing lacuna. The review summarizes the available knowledge of xanthine based drugs development along with exploring new xanthine led chemical synthesis path for bringing diversification in xanthine based research. The main objective of this review is to explore the immense potential of xanthine as scaffold in drug development.

Pharmacological potential of methylxanthines: Retrospective analysis and future expectations

Methylated xanthines (methylxanthines) are available from a significant number of different botanical species. They are ordinarily included in daily diet, in many extremely common beverages and foods. Caffeine, theophylline and theobromine are the main methylxanthines available from natural sources. The supposedly relatively low toxicity of methylxanthines, combined with the many beneficial effects that have been attributed to these compounds through time, generated a justified attention and a very prolific ground for dedicated scientific reports. Methylxanthines have been widely used as therapeutical tools, in an intriguing range of medicinal scopes. In fact, methylxanthines have been/were medically used as Central Nervous System stimulants, bronchodilators, coronary dilators, diuretics and anti-cancer adjuvant treatments. Other than these applications, methylxanthines have also been hinted to hold other beneficial health effects, namely regarding neurodegenerative diseases, cardioprotection, diabetes and fertility. However, it seems now consensual that toxicity concerns related to methylxanthine consumption and/or therapeutic use should not be dismissed. Taking all the knowledge and expectations on the potential of methylxanthines into account, we propose a systematic look at the past and future of methylxanthine pharmacologic applications, discussing all the promise and anticipating possible constraints. Anyways, methylxanthines will still substantiate considerable meaningful research and discussion for years to come.

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.

Comparative study of the efficacy and safety of theophylline and doxofylline in patients with bronchial asthma and chronic obstructive pulmonary disease

BACKGROUND

Bronchial asthma and chronic obstructive pulmonary disease (COPD) are the major obstructive disorders that may contribute to the severity in individual patients. The present study was designed to compare the efficacy and safety of theophylline and doxofylline in patients with bronchial asthma and COPD.

METHODS

A total of 60 patients, 30 each with bronchial asthma and COPD, were enrolled for the study. Each group of 30 patients received standard treatment for asthma and COPD. Each group was again subdivided into two with 15 patients each, who received theophylline or doxofylline in addition to standard therapy, for a period of 2 months. Each patient was followed up fortnightly for the assessment of efficacy parameters using a pulmonary function test (PFT), clinical symptoms and emergency drug use, and safety was assessed by recording adverse drug reactions.

RESULTS

Both theophylline and doxofylline produced enhancements in PFT at different time intervals in both asthma and COPD patients. The maximum beneficial effects were seen at 6 weeks for asthma patients and at 8 weeks for COPD patients for both theophylline and doxofylline.

CONCLUSIONS

The comparative study showed that doxofylline was more effective as evidenced by improvement in PFT as well as clinical symptoms, and reduced incidence of adverse effects and emergency bronchodilator use.

The potential of methylxanthine-based therapies in pediatric respiratory tract diseases

Caffeine, theophylline and theobromine are the most known methylxanthines as they are present in coffee, tea and/or chocolate. In the last decades, a huge experimental effort has been devoted to get insight into the variety of actions that these compounds exert in humans. From such knowledge it is known that methylxanthines have a great potential in prevention, therapy and/or management of a variety of diseases. The benefits of methylxanthine-based therapies in the apnea of prematurity and their translational potential in pediatric affections of the respiratory tract are here presented.

Doxofylline and theophylline: a comparative clinical study

OBJECTIVES

COPD is one of the major public health problems worldwide. Theophylline has been used in the treatment of COPD for decades. Doxofylline a new theophylline congener has been claimed to have better safety profile. The study was undertaken to compare theophylline and doxophylline at doses recommended and commonly used in clinical practice.

METHODS

The study was conducted in patients of COPD in TB chest department of a medical college hospital. It was randomized, prospective and open label. A total of 154 patients were divided in two group .Group I was administered 400 mg theophylline SR once daily and group II was administered doxofylline 400 mg twice a day orally. Spirometric variables symptom score, and adverse effects were recorded on day 0, 7 and 21 of therapy. Data were compared and analysed using SPSS version 16.

RESULTS

Results of the study showed that there was no statistically significant difference with respect to spirometric variables and symptom score in the two groups and there was no significant difference in two groups with respect to side effects (p>0.05).

CONCLUSIONS

It is concluded that doxophylline has no advantage over theophylline in terms of either efficacy or safety on the doses commonly used in current clinical practice.

The mechanism of action of doxofylline is unrelated to HDAC inhibition, PDE inhibition or adenosine receptor antagonism

Xanthines such as theophylline have been used in the treatment of lung diseases since the early 1900's, but have a major drawback of a very narrow therapeutic window and many drug/drug interactions. This means that plasma levels have to be measured regularly and can make the use of theophylline problematic. With the increasing availability of other classes of drugs for the treatment of respiratory diseases, this has limited the use of xanthines, despite their clear clinical benefit in the treatment of patients with asthma and COPD. Doxofylline is a xanthine molecule having both bronchodilator and anti-inflammatory activity with an improved therapeutic window over conventional xanthines such as theophylline. However, the mechanistic basis of this improved therapeutic window is not understood. The present study has investigated some pharmacological activities of doxofylline in comparison with theophylline. Doxofylline does not directly inhibit any of the known HDAC enzymes, and did not inhibit any PDE enzyme sub types or act as an antagonist at any of the known adenosine receptors, except for PDE2A(1), and adenosine A(2A) and only at the highest tested concentration (10(-4) M). These results may explain the improved tolerability profile of doxofylline compared with theophylline.

Stability and compatibility of doxofylline with phentolamine mesilate in 0.9% sodium chloride or 5% dextrose injection for intravenous infusion

WHAT IS KNOWN AND OBJECTIVE

The use of extemporaneously prepared admixtures of drugs must be supported by documentation of their chemical stability. The objective was to assess the physical compatibility and the chemical stability of doxofylline with phentolamine mesilate in 0.9% sodium chloride or 5% dextrose injection for intravenous infusion.

METHODS

Total volumes of 20 and 1 mL of doxofylline solution and phentolamine mesilate solution, respectively, were added to 250 mL polyolefin bags containing 5% dextrose injection or 0.9% sodium chloride injection. Bags were stored for 24 h at 20-25 °C. Chemical compatibility was measures with high-performance liquid chromatography, and physical compatibility was determined visually.

RESULTS

The samples were clear and colourless when viewed in normal fluorescent room light. The pH value and particulate content of the admixtures exhibited little change. The retentions of the initial concentration of doxofylline and phentolamine mesilate in the admixtures were within 97-105%. Doxofylline and phentolamine mesilate were stable in 5% dextrose injection or in 0.9% sodium chloride for up to 24 h at 20-25 °C.

WHAT IS NEW AND CONCLUSION

Doxofylline and phentolamine mesilate mixed in both 5% dextrose injection and 0.9% sodium chloride injection in 250 mL multilayer polyolefin bags at concentrations of 0.74 mg/mL and 36.9 μg/mL, respectively, were stable for up to 24 h at 20-25 °C.

Spectrophotometric and reversed-phase high-performance liquid chromatographic method for the determination of doxophylline in pharmaceutical formulations

Two methods are described for determination of Doxophylline in a solid dosage form. The first method was based on ultraviolet (UV)-spectrophotometric determination of the drug. It involves absorbance measurement at 274 nm (λ(max) of Doxophylline) in 0.1 N hydrochloric acid. The calibration curve was linear, with the correlation coefficient between 0.99 and 1.0 over a concentration range of 0.20-30 mg/ml for the drug. The second method was based on high-performance liquid chromatography (HPLC) separation of the drug in reverse-phase mode using the Hypersil ODS C(18) column (250 × 4.6 mm, 5 mm). The mobile phase constituted of buffer acetonitrile (80:20) and pH adjusted to 3.0, with dilute orthophosphoric acid delivered at a flow rate 1.0 ml/min. Detection was performed at 210 nm. Separation was completed within 7 min. The calibration curve was linear, with the correlation coefficient between 0.99 and 1.0 over a concentration range of 0.165-30 mg/ml for the drug. The relative standard deviation was found to be <2.0% for the UV-spectrophotometry and HPLC methods. Both these methods have been successively applied to the solid dosage pharmaceutical formulation, and were fully validated according to ICH guidelines.

Doxofylline: a promising methylxanthine derivative for the treatment of asthma and chronic obstructive pulmonary disease

BACKGROUND

Doxofylline, a methylxanthine derivative, has recently drawn attention because of its better safety profile and similar efficacy over the most widely prescribed analogue, theophylline, indicated for asthma and chronic obstructive pulmonary disease.

OBJECTIVE

This article attempts to discuss the pharmacodynamics/pharmacokinetics and clinical efficacy of doxofylline.

METHOD

An extensive search in three electronic databases (Unbound Medline, Pubmed and Sciencedirect) and internet search engines (Scirus and Google Scholar) were used to identify the clinical studies on doxofylline. The literature search was carried out without time constraints to ensure maximum coverage of existing literature on doxofylline.

RESULTS/CONCLUSION

In a relatively large number of comparative studies, doxofylline is indicated to have less affinity for alpha(1) and alpha(2) receptors than theophylline. Unlike theophylline, doxofylline does not antagonize calcium channels, nor does it interfere with the influx of calcium into the cells, which probably reduces the cardiac side effects. Moreover, it does not affect sleep rhythm, gastric secretions, heart rate and rhythm and CNS functioning. Numerous reports available regarding the better tolerability of doxofylline than theophylline prove it as a potential bronchodilator with promising pharmacological behavior. However, despite its superior safety and clinical efficacy, the potential of doxofylline has not been fully exploited.

Doxofylline: The next generation methylxanthine

Methylxanthines are widely used in the treatment of asthma. Being one of the few drugs that can be administered orally, they are especially helpful in resource restricted settings. Theophylline, the commonly used methylxanthine drug is associated with a wide range of adverse effects accounting for the poor compliance and high drop-out rates. Moreover, a narrow therapeutic index warrants routine monitoring of its levels in the blood. Doxofylline, a new methylxanthine derivative, is shown to have similar efficacy with significantly less side effects in both animal studies as well as human adults. However, there is a paucity of studies in children with asthma. Retrospective data suggest that 11% patients experienced some side effects, but only 5% reported moderate side effects. Available evidence suggests that it improves spirometric parameters in children with asthma as compared to placebo. Extrapolating data from adult patients, it may be used in place of theophylline as an add on therapy in step 3 and step 4 in children with asthma. Dosage recommended for children> 6 yrs of age is 6 mg/Kg/dose BID. Doxofylline produces stable serum concentrations, hence plasma monitoring is required only in patients with hepatic insufficiency and intolerance to xanthine drugs.

Oral theophylline for chronic obstructive pulmonary disease

BACKGROUND

Oral theophylline has, for many years, been used as a bronchodilator in patients with COPD. Despite the introduction of new drugs, and its narrow therapeutic index, theophylline is still recommended for COPD treatment.

OBJECTIVES

To determine the effectiveness of oral theophylline when compared to placebo in patients with stable COPD.

SEARCH STRATEGY

The Cochrane Airways Review Group and Cochrane Controlled Clinical Registers were searched.

SELECTION CRITERIA

All studies were randomised controlled trials (RCTs).

DATA COLLECTION AND ANALYSIS

Data were independently abstracted and the methodological quality assessed by two reviewers.

MAIN RESULTS

Twenty RCTs met the inclusion criteria. Concomitant therapy varied from none to any other bronchodilator plus corticosteroid (oral and inhaled). The following outcomes were significantly different when compared to placebo. FEV1 improved with treatment: Weighted Mean Difference (WMD) 100 ml; 95% Confidence Interval (95%CI) 40, 160 ml. Similarly for FVC: WMD 210 ml 95%CI 100, 320. Two studies reported an improvement in VO2max; WMD 195 ml/min, 95%CI 113,27). At rest, PaO2 and PaCO2 both improved with treatment (WMD 3.2 mmHg; 95%CI = 1.2, 5., and WMD -2.4 mmHg; 95%CI = -3.5, -1.2, respectively). Walking distance tests did not improve (4 studies, Standardised Mean Difference 0.30, 95%CI -0.01, 0.62), neither did Visual Analogue Score for breathlessness isn two small studies (WMD 3.6, 95%CI -4.6, 11.8). The Relative Risk (RR) of nausea was greater with theophylline (RR 7.7; 95%CI 1.5, 39.9). However, patients' preference for theophylline was greater than that for placebo (RR 2.27; 95%CI = 1.26, 4.11). Very few patient withdrew from these studies for any reason.

REVIEWER'S CONCLUSIONS

Theophylline has a modest effect on FEV1 and FVC and slightly improves arterial blood gas tensions in moderate to severe COPD. These benefits were seen in patients receiving a variety of different concomitant therapies. Improvement in exercise performance depended on the method of testing. There was a very low dropout rate in the studies that could be included in this review, which suggests that recruited patients may have been known by the investigators to be theophylline tolerant. This may limit the generalisability of these studies.