Theophylline. A review of its potential steroid sparing effects in asthma

An investigation of the drug release kinetics of 3D-Printed two compartment Theophylline and Prednisolone tablets

Pharmaceutical 3D printing (3DP) not only offers the possibility of dose personalization but also the co-administration of multiple active pharmaceutical ingredients (APIs) in one combination tablet. In this study, Theophylline (TPH) and Prednisolone (PSL) were printed as bi-tablets, which are single tablets with two distinct separate compartments. New findings show that the combination therapy of TPH with systemic corticosteroids shows a highly synergistic effect in the treatment of pulmonary diseases. For TPH, a drug with a narrow therapeutic window (NTW), precise sustained release requirements are mandatory, while PSL requires immediate drug release and is individually administered in doses specifically tied to the treatment progression. The study aims to understand the extent to which the combination of two tablet compartments influences the individual drug dissolution kinetics of the respective single compartments. Utilizing a full factorial statistical experimental design, various practically relevant doses were produced, investigated for their drug release, analyzed using different mathematical model fits, and compared with respective mono-tablets. The results show that the sustained drug release of TPH is not significantly influenced by the addition of a second compartment in relationship to respective doses. Individualization of bi-tablet doses while maintaining similar release profiles is possible with the given design setup, as release curves still show high similarity. In all tablet designs, PSL release occurred sufficiently fast, with the release rate correlating to the surface area-to-volume ratio (SA/V) as the main determining parameter.

Deoxygenative gem-difluorovinylation of aliphatic alcohols

An unprecedented deoxygenative gem-difluorovinylation of aliphatic alcohols using α-trifluoromethyl alkenes is achieved under photocatalytic conditions. Inexpensive Ph₃P acts as an efficient O-atom transfer reagent to facilitate the deoxygenation of alcohols for the generation of reactive alkyl radical species. Remarkable features of this reaction include mild conditions, simple operation and broad scope. The synthetic utility of this reaction was validated by the success of two-step one-pot reactions, scale-up synthesis and chemoselective monodeoxygenation of diols.

Pharmacology and Therapeutics of Bronchodilators Revisited

Bronchodilators remain the cornerstone of the treatment of airway disorders such as asthma and chronic obstructive pulmonary disease (COPD). There is therefore considerable interest in understanding how to optimize the use of our existing classes of bronchodilator and in identifying novel classes of bronchodilator drugs. However, new classes of bronchodilator have proved challenging to develop because many of these have no better efficacy than existing classes of bronchodilator and often have unacceptable safety profiles. Recent research has shown that optimization of bronchodilation occurs when both arms of the autonomic nervous system are affected through antagonism of muscarinic receptors to reduce the influence of parasympathetic innervation of the lung and through stimulation of β 2-adrenoceptors (β 2-ARs) on airway smooth muscle with β 2-AR-selective agonists to mimic the sympathetic influence on the lung. This is currently achieved by use of fixed-dose combinations of inhaled long-acting β 2-adrenoceptor agonists (LABAs) and long-acting muscarinic acetylcholine receptor antagonists (LAMAs). Due to the distinct mechanisms of action of LAMAs and LABAs, the additive/synergistic effects of using these drug classes together has been extensively investigated. More recently, so-called "triple inhalers" containing fixed-dose combinations of both classes of bronchodilator (dual bronchodilation) and an inhaled corticosteroid in the same inhaler have been developed. Furthermore, a number of so-called "bifunctional drugs" having two different primary pharmacological actions in the same molecule are under development. This review discusses recent advancements in knowledge on bronchodilators and bifunctional drugs for the treatment of asthma and COPD. SIGNIFICANCE STATEMENT: Since our last review in 2012, there has been considerable research to identify novel classes of bronchodilator drugs, to further understand how to optimize the use of the existing classes of bronchodilator, and to better understand the role of bifunctional drugs in the treatment of asthma and chronic obstructive pulmonary disease.

Histone deacetylase 2 (HDAC2) attenuates lipopolysaccharide (LPS)-induced inflammation by regulating PAI-1 expression

Background

Sepsis is a life-threatening organ dysfunction caused by dysregulated host response to infection, and is primarily characterized by an uncontrolled systemic inflammatory response. In the present study, we developed an effective adjunct therapy mediated by a novel mechanism, to attenuate overt inflammation. LPS-treated macrophages were adopted as an in vitro model of endotoxin-induced inflammation during sepsis. Experiments were carried out using primary mouse peritoneal macrophages and the murine macrophage cell line RAW264.7, to elucidate the mechanisms by which HDAC2 modulates endotoxin-induced inflammation.

Results

Results revealed that PAI-1, TNF, and MIP-2 expression were inhibited by theophylline, an HDAC2 enhancer, in a RAW macrophage cell line, following LPS-induced inflammation. Thus, HDAC2 plays an important role in immune defense by regulating the expression of inflammatory genes via the c-Jun/PAI-1 pathway. During LPS-induced inflammation, overexpression of HDAC2 was found to inhibit PAI-1, TNF, and MIP-2 expression. Following LPS stimulation, HDAC2 knockdown increased nuclear translocation and DNA binding of c-Jun to the PAI-1 gene promoter, thereby activating PAI-1 gene transcription. Furthermore, inhibition of PAI-1 by TM5275 alone or in combination with theophylline notably suppressed TNF and MIP-2 expression.

Conclusion

HDAC2 can attenuate lipopolysaccharide-induced inflammation by regulating c-Jun and PAI-1 expression in macrophages.

Theophylline action on primary human bronchial epithelial cells under proinflammatory stimuli and steroidal drugs: a therapeutic rationale approach

Theophylline is a natural compound present in tea. Because of its property to relax smooth muscle it is used in pharmacology for the treatment of airway diseases (ie, chronic obstructive pulmonary disease, asthma). However, this effect on smooth muscle is dose dependent and it is related to the development of side effects. Recently, an increasing body of evidence suggests that theophylline, at low concentrations, also has anti-inflammatory effects related to the activation of histone deacetylases. In this study, we evaluated the effects of theophylline alone and in combination with corticosteroids on human bronchial epithelial cells under inflammatory stimuli. Theophylline administrated alone was not able to reduce growth-stimulating signaling via extracellular signal-regulated kinases activation and matrix metalloproteases release, whereas it strongly counteracts this biochemical behavior when administered in the presence of corticosteroids. These data provide scientific evidence for supporting the rationale for the pharmacological use of theophylline and corticosteroid combined drug.

Concurrent oral and inhalation drug delivery using a dual formulation system: the use of oral theophylline carrier with combined inhalable budesonide and terbutaline

A novel approach to concurrently deliver oral and inhaled drugs as a single formulation is presented. A triple therapy containing theophylline (THEO; orally delivered) with budesonide (BUD) and terbutaline (TERB; as single and co-spray-dried inhaled powders) was prepared as an ordered mix, with THEO acting as a carrier. The aerosolisation performance of THEO formulations containing BUD and TERB alone, physical mix and co-spray-dried powder was evaluated using a next-generation impactor (NGI). Physicochemical properties were investigated using electron microscopy, laser diffraction, dynamic vapour sorption and thermal analysis. NGI analysis indicated that >99 % of the THEO powder was >4.46 μm, with >90 % dissolved within 5 min. Particle size analysis showed TEB and BUD samples were of a suitable size for inhalation. Thermal and moisture analysis suggested powders to be stable at room temperature up to 70 % RH. Aerosol studies indicated a different performance of BUD and TERB depending on the mixing procedure. The co-spray-dried formulation showed the highest performance, with a fine particle fraction (≤4.46 μm) of BUD and TERB of 34.39 ± 3.56 and 33.61 ± 5.67 %, respectively. Such observations suggest that this multicomponent drug delivery system could be developed to concomitantly deliver oral and inhaled drugs, an approach that, to date, does not exist. Ultimately, this technology potentially reduces the requirement for multiple therapies and increases patient compliance.

Management of asthma during pregnancy

Asthma is an inflammatory lung condition that is the most common chronic disease affecting pregnancy. The changes in pulmonary physiology during pregnancy include increased minute ventilation, decreased functional residual capacity, increased mucus production, and airway mucosa hyperemia and edema. Pregnancy is also associated with a physiological suppression of the immune system. Many studies have described the heterogeneous immune system response in women with asthma during pregnancy, which partly explains why asthma has been shown to worsen, improve, or remain stable in equal proportions of women during pregnancy. Asthma may be associated with poor maternal and fetal outcomes. However, better maternal and fetal outcomes are observed with better asthma control. Asthma controller medications are generally thought to be safe during pregnancy, but limited data are available for some of the medicines. Newer medications like omalizumab open avenues for the treatment of asthma, but also pose a challenge, as there is limited experience with their use. Therefore, a multidisciplinary approach, including obstetricians, asthma specialists, and pediatricians should collaborate with the patient to carefully weigh the risks and benefits to determine an optimal management plan for each individual patient. The aim of this review article is to summarize the most recent literature about the immunological changes that occur during pregnancy, physiological and clinical implications of asthma on pregnancy, and asthma management and medication use in pregnant women.

Controversies Surrounding the Potential Use of Histone Deacetylase Inhibitors for the Treatment of Asthma

Management of asthma with long-acting β2-adrenergic receptor agonists and corticosteroids is exceptionally effective for the majority of asthma patients. However, corticosteroid insensitivity or resistance remains a significant clinical problem for a significant proportion of patients, requiring the investigation of new potential therapeutics for asthma. Histone deacetylase inhibitors represent a different class of compounds that have been evaluated for their potential antiasthmatic effects. Although accumulating evidence is indicating beneficial effects in rodent models of allergic airways disease, the potential use of histone deacetylase inhibitors in asthma remains controversial given their mechanisms of action. The aim of this paper is to provide an overview of histone deacetylases and pharmacological modifiers of these enzymes. The discussion represents a balanced account of the emerging evidence indicating the beneficial effects of histone deacetylase inhibitors in inflammatory lung diseases. The potential problems associated with the use of this class of compounds in asthma are also carefully considered.

Histone deacetylases and their role in asthma

OBJECTIVE

The aim of this article is to provide an overview of the classical histone deacetylase (HDAC) enzymes and HDAC inhibitors. The discussion is focused on the potential anti-asthmatic effects of this group of compounds.

METHODS

Medline was used with the search terms, "asthma and HDAC," "asthma and Trichostatin A," "asthma and valproic acid," "allergic airways disease and HDAC," "allergic airways disease and Trichostatin A," and "allergic airways disease and valproic acid." Manuscripts from the past decade were accessed. Historical literature dating from the 1960s was accessed for the use of anti-epileptics in the treatment of asthma.

RESULTS

Preliminary clinical trials with anti-epileptic drugs including the well-known HDAC inhibitor, valproic acid, have shown long-lasting anti-asthmatic effects providing the basis for the evaluation of this class of compounds in asthma. Studies using the prototypical HDAC inhibitor, Trichostatin A, in well-established murine models of allergic airways disease have also indicated beneficial effects.

CONCLUSION

Although the precise mechanisms are still controversial, inhibition of airway hyperresponsiveness and agonist-induced contraction as well as anti-inflammatory effects have been described for HDAC inhibitors in asthma.

Nanosized rods agglomerates as a new approach for formulation of a dry powder inhaler

Background:

Nanosized dry powder inhalers provide higher stability for poorly water-soluble drugs as compared with liquid formulations. However, the respirable particles must have a diameter of 1–5 μm in order to deposit in the lungs. Controlled agglomeration of the nanoparticles increases their geometric particle size so they can deposit easily in the lungs. In the lungs, they fall apart to reform nanoparticles, thus enhancing the dissolution rate of the drugs. Theophylline is a bronchodilator with poor solubility in water.

Methods:

Nanosized theophylline colloids were formed using an amphiphilic surfactant and destabilized using dilute sodium chloride solutions to form the agglomerates.

Results:

The theophylline nanoparticles thus obtained had an average particle size of 290 nm and a zeta potential of −39.5 mV, whereas the agglomerates were 2.47 μm in size with a zeta potential of −28.9 mV. The release profile was found to follow first-order kinetics (r² > 0.96). The aerodynamic characteristics of the agglomerated nanoparticles were determined using a cascade impactor. The behavior of the agglomerate was significantly better than unprocessed raw theophylline powder. In addition, the nanoparticles and agglomerates resulted in a significant improvement in the dissolution of theophylline.

Conclusion:

The results obtained lend support to the hypothesis that controlled agglomeration strategies provide an efficient approach for the delivery of poorly water-soluble drugs into the lungs.

Aminophylline for treating asthma and chronic obstructive pulmonary disease

Aminophylline is a complex of theophylline and ethylenediamine. Its main pharmacological action is relaxation of bronchial smooth muscle. Two meta-analyses examining the efficacy of aminophylline in acute asthma attacks in children and in adults have been reported by the Cochrane Collaboration. In the meta-analysis reporting results from studies in children, it was concluded that aminophylline does not add any benefit to standard care. Yet one study, which has the largest patient population, reports that aminophylline improves lung functions within 6-8 h and reduces the risk of intubation. The meta-analysis examining adult studies revealed that there is no outstanding difference between aminophylline and standard therapy in the management of adult acute asthma. In conclusion, aminophylline may be an alternative to intravenous infusion of beta-agonists, heliox or magnesium sulfate administration in children in whom respiratory fatigue begins to develop and intensive-care unit admission and mechanical ventilation seems to be the next treatment in line. However, in adults, it is not recommended for use in the treatment of acute asthma owing to its possible adverse effects.

Challenges of treating asthma in people who smoke

Cigarette smoking is common in asthma and is associated with poor symptom control and a reduced therapeutic response to inhaled and oral corticosteroids as compared with nonsmokers with asthma. This review examines the range of adverse health effects of smoking in asthma, the inflammatory mechanisms that may influence the efficacy of current drugs and discusses potential future therapeutic directions.

Theophylline

Theophylline (3-methyxanthine) has been used to treat airway diseases for over 70 years. It was originally used as a bronchodilator but the relatively high doses required are associated with frequent side effects, so its use declined as inhaled β₂-agonists became more widely used. More recently it has been shown to have anti-inflammatory effects in asthma and COPD at lower concentrations. The molecular mechanism of bronchodilatation is inhibition of phosphodiesterase(PDE)3 and PDE4, but the anti-inflammatory effect may be due to histone deacetylase (HDAC) activation, resulting in switching off of activated inflammatory genes. Through this mechanism theophylline also reverses corticosteroid resistance and this may be of particular value in severe asthma and COPD where HDAC2 activity is markedly reduced. Theophylline is given systemically (orally as slow-release preparations for chronic treatment and intravenously for acute exacerbations of asthma) and blood concentrations are determined mainly by hepatic metabolism, which may be increased or decreased in several diseases and by concomitant drug therapy. Theophylline is now usually used as an add-on therapy in asthma patients not well controlled on inhaled corticosteroids and in COPD patients with severe disease not controlled by bronchodilator therapy. Side effects are related to plasma concentrations and include nausea, vomiting and headaches due to PDE inhibition and at higher concentrations to cardiac arrhythmias and seizures due to adenosine A₁-receptor antagonism.

Apoptosis, airway inflammation and anti-asthma therapy: from immunobiology to clinical application

T lymphocyte apoptosis is essential for maintaining immune system homeostasis. Experimental evidence suggests apoptosis control mechanisms may be impaired in inflammatory conditions, particularly airway Th2-type allergic diseases. This review briefly examines the mucosal immune system homeostasis and common apoptotic pathways and discusses impaired apoptosis, allergy, airway inflammation, remodelling and fibrosis. Finally, the paper presents an update on pharmacological targeting of apoptosis to control airway inflammation in patients with allergic asthma.

Effect of theophylline on the rate of moderate to severe exacerbations among patients with chronic obstructive pulmonary disease

AIM

To determine the effectiveness of theophyllines in real clinical practice on moderate to severe exacerbations.

METHODS

A cohort of 36,492 chronic obstructive pulmonary disease (COPD) patients aged > or =50 years was reconstructed from the health administrative databases of the province of Quebec, Canada, between 1 January 1995 and 31 December 2002 to compare users of theophyllines with users of inhaled corticosteroids (ICS) and users of long-acting beta(2)-agonists (LABA) on their rate of moderate to severe COPD exacerbations.

RESULTS

Users of theophyllines were found to be less likely than users of LABA [crude rates 84 vs. 91 per 100 patient-years, adjusted rate ratio (RR) 0.89, 95% confidence interval (CI) 0.84, 0.95] and users of theophyllines plus ICS were found to be less likely than users of LABA plus ICS (crude rates 114 vs. 112 per 100 patient-years, adjusted RR 0.89, 95% CI 0.87, 0.92) to have moderate to severe COPD exacerbations. Users of theophyllines were found to be more likely than users of ICS to have a COPD exacerbation (crude rates 84 vs. 77 per 100 patient-years, adjusted RR 1.07, 95% CI 1.04, 1.10), and this association was even stronger among patients who had at least three exacerbations in the year prior to cohort entry (crude rates 273 vs. 213 per 100 patient-years, adjusted RR 1.28, 95% CI 1.19, 1.38).

CONCLUSION

The use of theophyllines was found to be associated with a reduction in the rate of COPD exacerbations among all COPD patients, but to be less effective than ICS among patients with frequent exacerbations.

Determination of caffeine and its metabolites in urine by capillary electrophoresis-mass spectrometry

The caffeine content of foods and beverages varies considerably, interfering with our ability to obtain valid interpretations in many human studies with regard to the mechanism of action(s) of caffeine and/or its metabolites. The rate of metabolism of caffeine and other xanthine drugs also varies greatly from one individual to another. Therefore, it is extremely important to develop accurate, reliable analytical methods to quantify caffeine and its metabolites in simple and complex matrixes. A simple method is described for the separation and characterization of caffeine and its major metabolites employing capillary electrophoresis (CE) coupled to ultraviolet-absorption and mass spectrometry (MS) detection. After optimization of the electrophoresis separation conditions, a reliable separation of caffeine and 11 of its major metabolites was achieved in 50 mM ammonium carbonate buffer, pH 11.0. The volatile aqueous electrolyte system used with a normal electroosmotic flow polarity also provided an optimal separation condition for the characterization of the analytes by MS. The CE method achieved baseline resolution for all 12 compounds in less than 30 min. The CE-MS method is suitable for use as a routine procedure for the rapid separation and characterization of caffeine and its metabolites. The usefulness of this method was demonstrated by the extraction, separation, and identification of caffeine and its 11 metabolites from normal urine samples. The urine specimens were first acidified to obtain optimum binding efficiency to the sorbents of the off-line, solid-phase extraction procedure employed here, and an acidified eluent solvent was employed for the desorption step to maximize the recovery of the bound analytes.

Pharmacokinetics and pharmacodynamics of systemically administered glucocorticoids

Glucocorticoids have pleiotropic effects that are used to treat diverse diseases such as asthma, rheumatoid arthritis, systemic lupus erythematosus and acute kidney transplant rejection. The most commonly used systemic glucocorticoids are hydrocortisone, prednisolone, methylprednisolone and dexamethasone. These glucocorticoids have good oral bioavailability and are eliminated mainly by hepatic metabolism and renal excretion of the metabolites. Plasma concentrations follow a biexponential pattern. Two-compartment models are used after intravenous administration, but one-compartment models are sufficient after oral administration.The effects of glucocorticoids are mediated by genomic and possibly nongenomic mechanisms. Genomic mechanisms include activation of the cytosolic glucocorticoid receptor that leads to activation or repression of protein synthesis, including cytokines, chemokines, inflammatory enzymes and adhesion molecules. Thus, inflammation and immune response mechanisms may be modified. Nongenomic mechanisms might play an additional role in glucocorticoid pulse therapy. Clinical efficacy depends on glucocorticoid pharmacokinetics and pharmacodynamics. Pharmacokinetic parameters such as the elimination half-life, and pharmacodynamic parameters such as the concentration producing the half-maximal effect, determine the duration and intensity of glucocorticoid effects. The special contribution of either of these can be distinguished with pharmacokinetic/pharmacodynamic analysis. We performed simulations with a pharmacokinetic/pharmacodynamic model using T helper cell counts and endogenous cortisol as biomarkers for the effects of methylprednisolone. These simulations suggest that the clinical efficacy of low-dose glucocorticoid regimens might be increased with twice-daily glucocorticoid administration.

Evaluation of cytokine modulators for asthma

Th2 cytokines play an important role in producing and maintaining airway inflammation in asthma. As a consequence, there is considerable interest in developing agents that modulate their effects. Therapeutic strategies include decreasing cytokine synthesis or release, blocking their effects by antibodies or soluble receptors, as well as administration of anti-inflammatory cytokines. Initial studies of three of these approaches have shown interesting results. The first is suplatast tosilate, a selective Th2-inhibitor that suppresses the synthesis of IL-4 and IL-5 in vitro. In a randomised double-blind placebo-controlled parallel study, suplatast, given orally TID, improved lung function and symptom control when added to inhaled beclomethasone for 4 weeks and prevented deterioration when the beclomethasone dose was decreased by 50% during a second 4 weeks. The second is CDP840, a second generation phosphodiesterase type 4 inhibitor, that may decrease the release of cytokines from eosinophils and Th2 lymphocytes. In a double-blind placebo-controlled crossover study, CDP840, given orally BID for 9 days, attenuated the late response to allergen by 30% when compared to placebo. The third is a recombinant human soluble IL-4 receptor (altrakincept) that neutralises endogenously produced IL-4. In inhaled steroid-dependent subjects, weekly nebulisation of altrakincept prevented lung function decline and asthma exacerbations after abrupt withdrawal of inhaled corticosteroids. In contrast, studies of anti-IL-5 monoclonal antibodies (mepolizumab and SCH55700) indicate that this strategy only partially depletes eosinophils from the bronchial mucosa and shows no benefit on clinical markers of asthma activity. Of these novel therapeutic approaches, inhibiting Th2 synthesis of IL-4 and IL-5 (suplatast) appears to offer the greatest potential and long-term studies of this approach should be undertaken.

Differential pharmacokinetics of theophylline in elderly patients

The clinical use of theophylline as a first-line bronchodilator has declined during the last two decades. However, in many clinical settings, such as an emergency bronchial asthma attack, theophylline may have a first-line role, in combination with beta(2)-adrenoreceptor agonists and corticosteroids, for improving the asthmatic status. Furthermore, many therapeutic mechanisms of theophylline for bronchial asthma have been reported, and recent studies have suggested that theophylline therapy may have a beneficial role in the management of chronic stable asthma as well as exacerbated disease. However, theophylline has a low therapeutic index because the bronchodilation it produces has a linear relationship with logarithmic increases in serum concentration for the therapeutic range of 5-20 mg/L. Thus, the knowledge of its basic pharmacokinetics and the factors that can alter its clearance is clinically relevant for physicians. Especially when used in elderly asthmatic patients, dosage adjustment of theophylline is a requisite since the elderly have several risk factors that may increase the plasma theophylline level, such as reduced clearance, various underlying diseases and multiple coadministered drugs. After theophylline treatment has been initiated, therapeutic drug monitoring is required.

A molecular mechanism of action of theophylline: Induction of histone deacetylase activity to decrease inflammatory gene expression

The molecular mechanism for the anti-inflammatory action of theophylline is currently unknown, but low-dose theophylline is an effective add-on therapy to corticosteroids in controlling asthma. Corticosteroids act, at least in part, by recruitment of histone deacetylases (HDACs) to the site of active inflammatory gene transcription. They thereby inhibit the acetylation of core histones that is necessary for inflammatory gene transcription. We show both in vitro and in vivo that low-dose theophylline enhances HDAC activity in epithelial cells and macrophages. This increased HDAC activity is then available for corticosteroid recruitment and predicts a cooperative interaction between corticosteroids and theophylline. This mechanism occurs at therapeutic concentrations of theophylline and is dissociated from phosphodiesterase inhibition (the mechanism of bronchodilation) or the blockade of adenosine receptors, which are partially responsible for its side effects. Thus we have shown that low-dose theophylline exerts an anti-asthma effect through increasing activation of HDAC which is subsequently recruited by corticosteroids to suppress inflammatory genes.

Safety of antileukotriene agents in asthma management

OBJECTIVE

This article presents information on the safety of zafirlukast, montelukast, and zileuton, three antileukotrienes (anti-LTs) approved in the United States for the prophylaxis and treatment of asthma. After reading this article, readers should have an understanding both of the general safety of anti-LTs and their specific adverse effects.

DATA SOURCES

Relevant and appropriate controlled clinical studies on the safety of anti-LTs in asthma were used. Only literature in the English language was reviewed.

STUDY SELECTION

Material was taken from academic/scholarly journals and appropriate reviews.

RESULTS

Antiasthma agents, including corticosteroids, beta2-agonists, and methylxanthines, may be categorized into two classes: those used for the long-term control and prevention of persistent asthma and those used for the prompt relief of acute symptoms and exacerbations of the disease. Although most agents are safe and well tolerated when used properly, adverse effects may occur with use at higher dose levels. The anti-LTs, including zafirlukast, montelukast, and zileuton, are the first new pharmacologic class in the therapeutic armamentarium for asthma management to be approved in the United States in the past 20 years. Both zafirlukast and montelukast carry pregnancy category B classification whereas zileuton carries pregnancy category C classification. The most common adverse effects observed in clinical trials were headache, pharyngitis, abdominal pain, dyspepsia, and cough.

CONCLUSIONS

The results of clinical trials and real-world experience indicate that these agents are generally safe and well tolerated, with an incidence of adverse effects comparable with placebo.

Montelukast: a review of its therapeutic potential in persistent asthma

Montelukast is a cysteinyl leukotriene receptor antagonist used to treat persistent asthma in patients aged > or = 6 years. The drug has a rapid onset of action. Improvements in lung function and reductions in as-needed beta2-agonist usage are apparent within 1 day of initiating montelukast treatment in adults and adolescents (aged > or = 15 years treated with 10 mg/day) or children (aged 6 to 14 years treated with 5 mg/day) with persistent asthma as shown in clinical trials. In two 12-week, multicentre, randomised, double-blind studies in adults and adolescents aged > or = 15 years with persistent asthma [forced expiratory volume in 1 second (FEV1) = 50 to 85% predicted] there was significantly (p < 0.05) greater improvement in FEV1, symptom scores, peak expiratory flow (PEF), as-needed beta2-agonist use, peripheral eosinophil counts and health-related quality of life (QOL) in patients treated with montelukast 10 mg/day than in recipients of placebo. Improvements were significantly greater in patients treated with inhaled beclomethasone 400 microg/day than in recipients of montelukast 10 mg/day in 1 of these studies. Nonetheless, 42% of montelukast recipients experienced > or = 11% improvement in FEV1, the median improvement in this parameter in beclomethasone-treated patients. In an 8-week multicentre, randomised, double-blind, study in children aged 6 to 14 years with persistent asthma (FEV1 50 to 85% predicted), montelukast 5 mg/day produced significantly greater improvements in FEV1, clinic PEF, as-needed beta2-agonist use, peripheral eosinophil counts, asthma exacerbations and QOL scores than placebo. The combination of montelukast 10 mg/day plus inhaled beclomethasone 200 microg twice daily provided significantly better asthma control than inhaled beclomethasone 200 microg twice daily in adults with poorly controlled asthma (mean FEV1 = 72% predicted) despite 4 weeks treatment with inhaled beclomethasone. Patients receiving the combination experienced significant improvements in FEV1 and morning PEF, significant reductions in daytime symptom scores, as-needed beta2 agonist usage and night-time awakenings with asthma, and had significantly lower peripheral blood eosinophil counts after 16 weeks in this multicentre, randomised, double-blind, placebo-controlled study. Among adults (FEV1 > or = 70%) treated with montelukast 10 mg/day for 12 weeks, inhaled corticosteroid dosages were titrated downward by 47% (vs 30% in placebo recipients), 40% of patients were tapered off of inhaled corticosteroids (vs 29%), and significantly fewer patients (16 vs 30%) experienced failed corticosteroid rescues in a multicentre, randomised, double-blind study. During clinical studies, the frequency of adverse events in montelukast-treated adults, adolescents and children was similar to that in placebo recipients. In conclusion, montelukast is well tolerated and effective in adults and children aged > or = 6 years with persistent asthma including those with exercise-induced bronchoconstriction and/or aspirin sensitivity. Furthermore, montelukast has glucocorticoid sparing properties. Hence, montelukast, as monotherapy in patients with mild persistent asthma, or as an adjunct to inhaled corticosteroids is useful across a broad spectrum of patients with persistent asthma.

Capillary electrophoretic analysis of alkaline phosphatase inhibition by theophylline

An analytical method for studying enzyme inhibition has been developed using capillary electrophoresis with laser-induced fluorescence detection. This technique is based on electrophoretic mixing of zones of enzyme and inhibitor in substrate-filled capillaries. Enzyme catalytic activity is measured by detecting the fluorescent reaction product as it migrates past the detector. Reversible enzyme inhibition is indicated by a transient decrease in product formation. The enzyme, alkaline phosphatase, has been studied using the fluorogenic substrate AttoPhos ([2,2'-bibenzothiazol]-6-hydroxy-benzthiazole phosphate). This assay has been used to quantify theophylline, a noncompetitive, reversible inhibitor of alkaline phosphatase. The detection limit for theophylline is estimated at 3 microM, and 8.6 amole of alkaline phosphatase are required for each assay. The calculated K(i) for theophylline is 90 microM for the capillary electrophoretic enzyme-inhibitor assays.

Phosphodiesterase 4 inhibitors and the treatment of asthma: where are we now and where do we go from here?

Research conducted over the last 20 years has established that inflammation of the airways is central to the airway dysfunction that characterises asthma. Typically, the airway wall is infiltrated by a variety of cells including mast cells, eosinophils and T lymphocytes, which have deviated towards a T(H)2 phenotype. Together, these cells release a plethora of mediators including interleukin (IL)-4, IL-5, granulocyte/macrophage colony-stimulating factor and eotaxin which ultimately cause the histopathology and symptoms of asthma. Glucocorticosteroids are the only drugs currently available that effectively impact upon this inflammation and resolve, to a greater or lesser extent, compromised lung function. However, steroids are nonselective and generally unsuitable for paediatric use. New drugs are clearly required. One group of potential therapeutic agents for asthma are inhibitors of cyclic AMP-specific phosphodiesterase (PDE), of which theophylline may be considered a prototype. It is now known that PDE is a generic term which refers to at least 11 distinct enzyme families that hydrolyse cAMP and/or cGMP. Over the last decade, inhibitors of PDE4 (a cAMP-specific family that negatively regulates the function of almost all pro-inflammatory and immune cells, and exerts widespread anti-inflammatory activity in animal models of asthma) have been developed with the view to reducing the adverse effects profile associated with non-selective inhibitors such as theophylline. Such is the optimism regarding PDE4 as a viable therapeutic target that more than 100 PDE4 inhibitor patent applications have been filed since 1996 by 13 major pharmaceutical companies. This article reviews the progress of PDE4 inhibitors as anti-inflammatory agents, and identifies problems that have been encountered by the pharmaceutical industry in the clinical development of these drugs and what strategies are being considered to overcome them.