Current issues in the use of theophylline

Decrease of the affinity of theophylline bind to serum proteins induced by flavonoids and their synergies on protein conformation

In this study, the single and simultaneous interactions of theophylline and flavonoids with human serum albumin (HSA) were studied by multi-spectroscopic and molecular docking approaches. The influences of flavonoids on the binding constant (K_b) and the binding distance (r) of theophylline bind to HSA were determined and the changes of HSA conformation caused by the synergies of theophylline and flavonoids were investigated. Because theophylline, rutin and baicalin are all bond to the same binding site, the competitive bind of theophylline and flavonoids to HSA leads to the reduction of the K_a value of theophylline binding to HSA. The addition of rutin and baicalin can increase the value of r of theophylline binding to HSA, which further confirm the existence of the competitive bind of theophylline and flavonoids to HSA. Additionally, the results of synchronous fluorescence, three-dimensional fluorescence and circular dichroism spectra indicate that the presence of rutin and baicalin can give rise to the further changes of HSA conformation. These results suggest that the intake of flavonoid-rich food and beverages can increase the serum concentrations of theophylline and induce a high incidence of toxic symptom in clinic.

Pneumocystis Carinii Pneumonia in Adult Non-HIV Disorders

Pneumocystis carinii pneumonia (PCP) remains a serious infection in the immunocompromised host (in the absence of HIV infection) and presents significant management and diagnostic challenges to ICU physicians. Non-HIV PCP is generally abrupt in onset, and follows a fulminate course with high rates of hospitalization, ICT admission, respiratory failure, and requirement for intubation. Mortality is generally high, especially if mechanical ventilation is required. Non-invasive ventilatory support may be considered, although the rapid progression to respiratory failure often necessitates intubation at the time of presentation. Bronchoscopy is often required to establish the diagnosis, and empirical antimicrobial treatment specifically targeted to P. carinii should be initiated while awaiting confirmation. Adjunctive corticosteroids may accelerate recovery, although their use has not yet been established in non-HIV PCP. For the ICU physicians to diagnose PCP, the non-specific presentation of an acute febrile illness and respiratory distress with diffuse pulmonary infiltrates requires a high clinical index of suspician, familiarity with clinical conditions associated with increased risk for PCP, and a low threshold for bronchoscopy to establish the diagnosis.

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.

A review of the use of adjunctive therapies in severe acute asthma exacerbation in critically ill children

Asthma is a common and potentially life threatening childhood condition. Asthma involves not only chronic airway remodeling, but may also include frequent exacerbations resulting from bronchospasm, edema, and mucus production. In children with severe exacerbations, standard therapy with β2-agonists, anti-cholinergic agents, oxygen, and systemic steroids may fail to reverse the severe airflow obstruction and necessitate use of adjunctive therapies. These therapies include intravenous or inhaled magnesium, inhaled helium-oxygen mixtures, intravenous methylxanthines, intravenous β2-agonists, and intravenous ketamine. Rarely, these measures are not successful and following the initiation of invasive mechanical ventilation, inhaled anesthetics or extracorporeal life support may be required. In this review, we discuss the mechanisms and evidence for adjunctive therapies in the setting of severe acute asthma exacerbations in children.

Therapeutic management of allergic diseases

Allergic diseases are characterized by the activation of inflammatory cells and by a massive release of mediators. The aim of this chapter was to describe succinctly the modes of action, indications, and side effects of the major antiallergic and antiasthmatic drugs. When considering the ideal pharmacokinetic characteristics of a drug, a poorly metabolized drug may confer a lower variability in plasma concentrations and metabolism-based drug interactions, although poorly metabolized drugs may be prone to transporter-based disposition and interactions. The ideal pharmacological properties of a drug include high binding affinity, high selectivity, and appropriate association and dissociation rates. Finally, from a patient perspective, the frequency and route of administration are important considerations for ease of use.

Administration of phosphodiesterase inhibitors and an adenosine A1 receptor antagonist induces phrenic nerve recovery in high cervical spinal cord injured rats

High cervical spinal cord hemisection interrupts the descending respiratory drive from the medulla to the ipsilateral phrenic motoneurons, consequently leading to the paralysis of the ipsilateral hemidiaphragm. Previous studies have shown that chronic oral administration of theophylline, a phosphodiesterase inhibitor and an adenosine receptor antagonist, can restore function to the quiescent phrenic nerve and hemidiaphragm ipsilateral to hemisection. Both of these actions of theophylline result in an increase in 3'-5'-cyclic adenosine monophosphate (cAMP). Furthermore, the chronic theophylline-mediated respiratory recovery persists long after the animals have been weaned from the drug. To date, the precise cellular mechanisms underlying the recovery induced by theophylline are still not known. Since theophylline has two modes of action, in the present study we tested whether chronic administration of pentoxifylline, a non-selective phosphodiesterase inhibitor, rolipram, a phosphodiesterase-4 specific inhibitor, and 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), an adenosine A1 receptor antagonist, would induce recovery similar to that induced by theophylline in male Sprague-Dawley rats following a left C2 spinal cord lesion. Recovery of left phrenic nerve activity was assessed at 5 or 10 days after the last drug administrations to assess the persistent nature of the recovery. Pentoxifylline, rolipram and DPCPX, all capable of modulating 3',5'-cyclic monophosphate (cAMP) levels, brought about long-term respiratory recovery in the phrenic nerve ipsilateral to the left C2 lesion at 5 and 10 days after the last drug administration. Therefore, these results suggest that compounds capable of regulating cAMP levels may be therapeutically useful in promoting functional recovery following spinal cord injury.

Theophylline versus terbutaline in treating critically ill children with status asthmaticus: a prospective, randomized, controlled trial

OBJECTIVE

To compare the efficacy of theophylline, terbutaline, or theophylline combined with terbutaline treatment in critically ill children with status asthmaticus who are already receiving continuous nebulized albuterol and intravenous corticosteroids.

DESIGN

Randomized, prospective, controlled, double-blind trial.

SETTING

Pediatric intensive care unit of a tertiary-care children's medical center.

PATIENTS

Forty critically ill children between the ages of 3 and 15 yrs with impending respiratory failure secondary to status asthmaticus.

INTERVENTIONS

All patients received intravenous methylprednisolone and continuous nebulized albuterol. The three study groups received theophylline plus placebo (group 1), terbutaline plus placebo (group 2), or theophylline and terbutaline together (group 3).

MEASUREMENTS AND MAIN RESULTS

Differences in baseline characteristics, change in clinical asthma score over time, length of pediatric intensive care unit stay, and incidence of adverse events were determined. The three study groups were similar in age, gender, race, asthma severity, and treatment. There were no differences in clinical asthma score over time, length of pediatric intensive care unit stay, or incidence of adverse events between the three groups, with the exception of a higher incidence of nausea in children in group 3. The median hospital cost of medication and theophylline blood levels was significantly lower in group 1 compared with groups 2 and 3 (280 US dollars vs. 3,908 US dollars vs. 4,045 US dollars, respectively, p < .0001).

CONCLUSIONS

Theophylline, when added to continuous nebulized albuterol therapy and intravenous corticosteroids, is as effective as terbutaline in treating critically ill children with status asthmaticus. The addition of theophylline to baseline therapy is more cost-effective when compared with terbutaline alone or terbutaline and theophylline together. Theophylline should be considered for use early in the management of critically ill asthmatic children.

Pneumocystis jiroveci Pneumonia in Adult Patients with AIDS

Pneumocystis jiroveci (P. carinii) is an opportunistic pathogen that has gained particular prominence since the onset of the AIDS epidemic. Among several important advances in diagnosis and management, appropriately targeting chemoprophylaxis to HIV-infected patients at high clinical risk for P. jiroveci pneumonia and the introduction of effective combination anti-retroviral therapy (including highly active antiretroviral therapy [HAART]) have contributed to the reduced incidence of P. jiroveci pneumonia. Despite the success of these clinical interventions, P. jiroveci pneumonia remains the most common opportunistic pneumonia and the most common life-threatening infectious complication in HIV-infected patients. Trimethoprim/sulfamethoxazole (cotrimoxazole) remains the first-line agent for effective therapy and chemoprophylaxis, and corticosteroids represent an important adjunctive agent in the treatment of moderate-to-severe P. jiroveci pneumonia. However, problems of chemoprophylaxis and treatment failures, high rates of adverse drug reactions and drug intolerance to first-line antimicrobials, high rates of relapse or recurrence with second-line agents, and newer concerns about the development of P. jiroveci drug resistance represent formidable challenges to the management and treatment of AIDS-related P. jiroveci pneumonia. With the expanding global problem of HIV infection, the intolerance or unavailability of HAART to many individuals and limited access to healthcare for HIV-infected patients, P. jiroveci pneumonia will remain a major worldwide problem in the HIV-infected population. New drugs under development as anti-Pneumocystis agents such as echinocandins and pneumocandins, which inhibit beta-glucan synthesis, or sordarins, which inhibit fungal protein synthesis, show promise as effective agents. Continued basic research into the biology and genetics of P. jiroveci and host defense response to P. jiroveci will allow the development of newer antimicrobials and immunomodulatory therapeutic agents to more effectively treat life-threatening pneumonia caused by this organism.

Nocturnal asthma uncontrolled by inhaled corticosteroids: theophylline or long-acting beta2 agonists?

Asthma is an inflammatory disease of the airways that is frequently characterised by marked circadian rhythm. Nocturnal and early morning symptoms are quite common among patients with asthma. Increased mortality and decreased quality of life are associated with nocturnal asthma. Although numerous mechanisms contribute to the pathophysiology of nocturnal asthma, increasing evidence suggests the most important mechanisms relate to airway inflammation. According to international guidelines, patients with persistent asthma should receive long term daily anti-inflammatory therapy. A therapeutic trial with anti-inflammatory therapy alone (without a long-acting bronchodilator) should be assessed to determine if this therapy will eliminate nocturnal and early morning symptoms. If environmental control and low to moderate doses of inhaled corticosteroids do not eliminate nocturnal symptoms, the addition of a long-acting bronchodilator is warranted. Long-acting inhaled beta2 agonists (e.g. salmeterol, formoterol) are effective in managing nocturnal asthma that is inadequately controlled by anti-inflammatory agents. In addition, sustained release theophylline and controlled release oral beta2 agonists are effective. In patients with nocturnal symptoms despite low to high doses of inhaled corticosteroids, the addition of salmeterol has been demonstrated to be superior to doubling the inhaled corticosteroid dose. In trials comparing salmeterol with theophylline, 3 studies revealed salmeterol was superior to theophylline (as measured by e.g. morning peak expiratory flow, percent decrease in awakenings, and need for rescue salbutamol), whereas 2 studies found the therapies of equal efficacy. Studies comparing salmeterol to oral long-acting beta2 agonists reveal salmeterol to be superior to terbutaline and equivalent in efficacy to other oral agents. Microarousals unrelated to asthma are consistently increased when theophylline is compared to salmeterol in laboratory sleep studies. In addition to efficacy data, clinicians must weigh benefits and risks in choosing therapy for nocturnal asthma. Long-acting inhaled beta2 agonists are generally well tolerated. If theophylline therapy is to be used safely, clinicians must be quite familiar with numerous factors that alter clearance of this drug, and they must be prepared to use appropriate doses and monitor serum concentrations. Comparative studies using validated, disease specific quality of life instruments (e.g. Asthma Quality of Life Questionnaire) have shown long-acting inhaled beta2 agonists are preferred to other long-acting bronchodilators. Examination of costs for these therapeutic options reveals that evening only doses of long-acting oral bronchodilators are less expensive than multiple inhaled doses. However, costs of monitoring serum concentrations, risks, quality of life and otheroutcome measures must also be considered. Long-acting inhaled beta2 agonists are the agents of choice for managing nocturnal asthma in patients who are symptomatic despite anti-inflammatory agents and other standard management (e.g. environmental control). These agents offer a high degree of efficacy along with a good margin of safety and improved quality of life.

Regulation of human mast cell and basophil function by cAMP

1. Mast cells and basophils are important in mediating allergic disorders such as asthma. Activation of these cells results in the release of a wide variety of mediators that can promote inflammatory responses. 2. Receptor-mediated activators of adenylate cyclase such as the beta-adrenoceptor agonist, isoprenaline, and prostaglandin E2 (PGE2) are effective at inhibiting mediator release from human lung mast cells (HLMC) but not basophils. In HLMC, both isoprenaline and PGE2 elevate and sustain increases in cyclic adenosine 3',5'-monophosphate (cAMP) whereas in basophils, both compounds cause transient increases in cAMP. 3. Non-selective inhibitors of phosphodiesterase (PDE) such as theophylline and 3-isobutyl-1-methylxanthine are effective inhibitors of mediator release from both HLMC and basophils and both compounds cause elevations of cAMP that are sustained in both cell types. 4. Studies with selective inhibitors of PDE indicate that the cAMP-specific PDE, PDE 4, regulates the activity of basophils but not HLMC. The nature of the PDE regulating HLMC responses is uncertain. 5. These data indicate that agents that induce and sustain elevations in intracellular cAMP attenuate the stimulated release of mediators from mast cells and basophils. However, the responsiveness of HLMC and basophils to selected cAMP-active agents differs.

Effects of theophylline on respiratory drive in patients with chronic obstructive pulmonary disease

Effects of theophylline administration on the respiratory drive were studied in seven patients with chronic obstructive pulmonary disease (COPD). End tidal CO2 (PetCO2), minute ventilation (Ve), forced expiratory volume in one second (FEV1), forced vital capacity (FVC), oxygen consumption (VO2), carbon dioxide output (VCO2), serum theophylline level (STL), ventilatory response (VeR), and mouth occlusion pressure response (OPR) to rise in PetCO2 on rebreathing were measured before and at 2-hour intervals after oral administration of 5 mg/kg anydrous theophylline or placebo. Mouth occlusion pressure response and VeR showed c significant increase after theophylline but not after placebo. Significant positive correlation between changes (delta) in STL and OPR (delta OPR = 0.025 + 0.8 delta STL; SEE = 1; r = 0.4; P < 0.005) and between STL and VeR (VeR = 0.82 + 0.055 STL +/- SEE = 0.7; r = 0.46; P < 0.01) and an inverse correlation between delta STL and delta PetCO2 (delta PetCO2 = 13.8 - 0.59 delta STL; SEE = 9.1; r = 0.61; P < 0.001) were noted. There was no correlation between the indices of respiratory drive and FEV1, Ve, VO2, or VCO2. It is concluded that theophylline increases respiratory drive in clinically employed doses independently of its bronchodilator or metabolic effects.

Pneumocystis carinii: an atypical fungal micro-organism

The purpose of this review is to assist mycologists in having a better understanding of Pneumocystis carinii and the disease that it causes. Now considered to be a fungus, P. carinii is unusual in its life cycle and relationship with the host. P. carinii pneumonia (PCP) pathogenesis, immunology and host defence mechanisms are examined, as well as epidemiological and control strategies. Most pneumocystosis pathophysiological changes result from the parasite's attachment and proliferation in the lungs, resulting in a filling of the alveoli with masses of the micro-organism. Pathological changes include an increase in alveolar capillary membrane permeability and injury to the alveolar epithelium, which may be mediated by the release of degradative enzymes from the pathogen. A host response takes place by hypertrophy, and hyperplasia involving type II epithelial alveolar cells. P carinii interacts with pulmonary surfactants by binding to the hydrophilic proteins A and D, and by modifying their phospholipid composition. Alveolar macrophages and CD4+ T cells play a key role in the host's defence against Pneumocystis. The epidemiology of PCP remains poorly understood. Airborne transmission has been established, but the actual infective form and its source remains unknown. Studies concerning P. carinii genetic diversity have shown that the parasite polymorphism is related, at least partially, to the host species. A strong host-species specificity in P. carinii has been found. From an epidemiological perspective, there appears to be no animal reservoir for the agent of human PCP. Thus, this disease should not be considered to be zoonotic. Although a significant decrease in the incidence of pneumocystosis has been obtained when employing chemoprophylaxis, anti-P. carinii drugs are not completely successful, often inducing deleterious side-effects. For these reasons, new prophylactic and therapeutic strategies need to be developed. One approach could be based on the anti-P. carinii effect of yeast killer toxins and antibiotic anti-idiotypic antibodies.

Goals of asthma management. A step-care approach

The past 15 years have seen a rise in mortality and morbidity resulting from asthma, despite a concurrent rise in general knowledge about the disease. The step-care strategy recognized these changes in its approach to asthma management; however, this approach should be used only with attempts to control environmental allergens. Step-care therapy requires that patients be categorized by the severity of illness. Step-one therapy is used for mild, infrequent symptoms and involves treatment based primarily on inhaled bronchodilators. Step-two therapy is instituted in all asthmatics except the mildest cases; it involves treatment by inhaled corticosteroids, cromolyn, or nedocromil. Step-three treatment targets cases of severe asthma through the use of oral corticosteroids. In all phases of treatment, however, it should be remembered that patient education is of critical importance. Education improves patient compliance and is critical to the successful treatment of asthma.

Application of population pharmacokinetics to the optimization of theophylline therapy

The aim of this study was to determine theophylline clearance (Cl) values in adult patients using serum concentrations gathered from routine clinical care. This information was used to estimate an a priori dosing regimen that would permit steady-state concentrations of 5-15 mg/litre, now recommended for the treatment of chronic asthma, and to evaluate the need to establish monitoring strategies when theophylline is given at these lower doses and when it can be expected that almost no adverse effects are likely. Retrospective data from 204 asthmatic and COPD patients, with a total of 517 serum concentrations, were studied. Population pharmacokinetic analysis was performed with the MULTI(ELS) computer program according to a one-compartment model. The influence of the following factors on theophylline Cl were investigated: body weight (TBW, IBW and LBM) and age as continuous variables, and gender, smoking habit and the presence of congestive heart failure (CHF) as indicator variables. To validate the results of the population pharmacokinetic analysis, a second independent group of 63 patients was studied prospectively. Hypothesis testing to evaluate potentially significant factors produced a final model in which Cl was based on IBW (kg) and age (years), and was reduced by 25% in patients with moderate CHF and increased by 28% in patients who smoked (Cl (litres/h) = (0.037 IBW-0.006 age) x 1.284 smoke x 0.751 CHF). The variability in Cl, expressed as the coefficient of variation, was 36%. In adult non-smoker and non-CHF patients, application of a maintenance dosing regimen calculated from IBW and age using the final model for Cl would theoretically afford only 1.5% of patients with potentially toxic concentrations. Thus, measurement of serum theophylline concentrations (STC) would only be required when other conditions known to alter theophylline metabolism exist, such as smoking or disease factors. These appreciations could have important clinical implications at a time when the potential immunomodulatory activity of theophylline is being emphasized and health resources should be allocated properly.

Differential effects of non-selective and selective phosphodiesterase inhibitors on human eosinophil functions

1. The effect of non-selective (3-isobutyl-1-methylxanthine, IBMX; theophylline) and type IV- or type III/IV-selective (rolipram, RP 73401; zardaverine, tolafentrine) phosphodiesterase (PDE) inhibitors on human eosinophil functions was investigated. 2. For this purpose human eosinophils were purified from blood of healthy donors by a magnetic cell separation (MACS) technique to a purity > or = 99%. From the stimuli investigated (complement C5a; N-formyl-methionyl-leucyl-phenylalanine, fMLP; platelet activating factor, PAF; opsonized zymosan) C5a was selected to test the influence of the above mentioned compounds on secretion of granule constituents (eosinophil cationic protein, ECP; eosinophil-derived neurotoxin, EDN) as well as on formation of reactive oxygen species measured by luminol-enhanced chemiluminescence in intact cells. For comparison, inhibition of PDE IV activity in the cytosol of disrupted cells, which contains about 75% of total PDE IV activity, was determined. 3. Both theophylline and IBMX inhibited the two cell responses with IC50 values which were in the range of their IC50 values obtained for inhibition of PDE IV activity in the cell-free system. The beta 2-adrenoceptor agonist, salbutamol (1 mumol l-1), which by itself did not substantially influence the two cell responses, only marginally improved the potency of theophylline and IBMX in inhibiting ECP/EDN secretion. Only the IC50 value of IBMX for inhibition of chemiluminescence was lowered by about one order of magnitude in the presence of salbutamol. 4. In contrast, none of the selective PDE inhibitors tested substantially inhibited the two cell responses at concentrations up to 10 mumol l-1. This was surprising because all of the compounds investigated inhibited PDE IV activity in the cell-free system with IC50 values which were at least 30 fold lower than the highest concentration of the compounds used with intact cells. In combination with salbutamol, however, both ECP/EDN secretion and chemiluminescence was inhibited by rolipram and zardaverine with IC50 values similar to the IC50 values for inhibition of PDE IV activity. Although RP 73401 and tolafentrine also inhibited both cell responses in the presence of salbutamol, the potency of these two compounds in inhibiting eosinophil function in intact cells was at least two orders of magnitude lower than would have been expected from the inhibition of PDE IV activity in the cell-free system. 5. These results indicate that (i) C5a-stimulated human eosinophils are sensitive to inhibition by then on-selective PDE inhibitors theophylline and IBMX, (ii) the inhibitory effect of these non-selective PDE inhibitors cannot be mimicked by selective PDE IV or PDE III/IV inhibitors although human eosinophils almost exclusively contain PDE IV; (iii) the selective PDE inhibitors need an additional cyclic AMP trigger like a beta 2-adrenoceptor agonist to be effective; but (iv) under the latter conditions inhibition of cell responses in intact cells does not correspond to inhibition of PDE IV activity in the cell-free system.6. We conclude that the non-selective PDE-inhibiting xanthines may inhibit C5a-stimulated human eosinophil responses by other action(s) in addition to PDE IV inhibition, and that inhibition of PDE IV activity in the cell-free system by the selective inhibitors may not generally represent the potency of the compounds in intact cells.

Pathogenesis and host response in Pneumocystis carinii pneumonia

Pneumocystis carinii (PC) pneumonia is recognized as the leading cause of opportunistic pulmonary infections in immunocompromised hosts during the past decade. Although much remains unknown about pathogenesis and host response in PC, recent years, studies of PC have provided us with an increasing base of knowledge about this organism and its relationship to the host. These studies have led to a better understanding of mechanisms of PC attachment and injury to host cells. New information about the interaction of PC with pulmonary surfactant provides insight about the pathophysiology of PC pneumonia. The interplay of the organism, host inflammatory cells, release of cytokines, generation of toxic metabolites, and involvement of both cellular and humoral immunity is complex, but understanding the pathogenesis of PC pneumonia is necessary in order to develop new therapies for this disorder.