History of the introduction of theophylline into the treatment of asthma

Plants derived therapeutic strategies targeting chronic respiratory diseases: Chemical and immunological perspective

The apparent predicament of the representative chemotherapy for managing respiratory distress calls for an obligatory deliberation for identifying the pharmaceuticals that effectively counter the contemporary intricacies associated with target disease. Multiple, complex regulatory pathways manifest chronic pulmonary disorders, which require chemotherapeutics that produce composite inhibitory effect. The cost effective natural product based molecules hold a high fervor to meet the prospects posed by current respiratory-distress therapy by sparing the tedious drug design and development archetypes, present a robust standing for the possible replacement of the fading practice of poly-pharmacology, and ensure the subversion of a potential disease relapse. This study summarizes the experimental evidences on natural products moieties and their components that illustrates therapeutic efficacy on respiratory disorders.

•

Plant derived therapeutics for managing chronic respiratory disorders.

•

Activity of natural product based molecules on key regulatory pathways of COPD.

•

Preclinical evidence for the efficacy of natural product moieties.

•

Clinical significance of plant derived molecules in pulmonary distress.

Phosphodiesterase inhibitors: history of pharmacology

The first pharmacological investigations of phosphodiesterase (PDE) inhibitors were developed with the clinical efficacies of drugs isolated from coffee, cacao and tea but only later their relevant ingredients were identified as xanthines that act as PDE. With its diuretic, inotropic and bronchodilating clinical efficacy, use of theophylline anticipated the clinical goals, which were later approached with the first-generation of weakly selective PDE inhibitors in the period from 1980 to 1990. Pharmacological and clinical research with these early compounds provided a vast pool of information regarding desired and adverse actions - although most of these new drugs had to be discontinued due to severe adverse effects. The pharmacological models for cardiac, vascular and respiratory indications were analysed for their PDE isoenzyme profiles, and when biochemical and molecular biological approaches expanded our knowledge of the PDE superfamily, the purified isoenzymes that were now available opened the door for more systematic studies of inhibitors and for generation of highly selective isoenzyme-specific drugs. The development of simple screening models and clinically relevant indication models reflecting the growing knowledge about pathomechanisms of disease are summarised here for today's successful application of highly selective PDE3, PDE4 and PDE5 inhibitors. The interplay of serendipitous discoveries, the establishment of intelligent pharmacological models and the knowledge gain by research results with new substances is reviewed. The broad efficacies of new substances in vitro, the enormous biodiversity of the PDE isoenzyme family and the sophisticated biochemical pharmacology enabled Viagra to be the first success story in the field of PDE inhibitor drug development, but probably more success stories will follow.

Intravenous aminophylline for acute severe asthma in children over two years receiving inhaled bronchodilators

BACKGROUND

Since the advent of inhaled beta2-agonists, anticholinergic agents and glucocorticoids, the role of aminophylline in paediatric acute asthma has become less clear. There remains some consensus that it is beneficial in children with acute severe asthma, receiving maximised therapy (oxygen, inhaled bronchodilators, and glucocorticoids).

OBJECTIVES

To determine if the addition of intravenous aminophylline produces a beneficial effect in children with acute severe asthma receiving conventional therapy.

SEARCH STRATEGY

The Cochrane Airways Group register of trials was used to identify relevant studies. The latest search was carried out in December 2004

SELECTION CRITERIA

Randomised-controlled trials comparing intravenous aminophylline with placebo in addition to usual care in children met the inclusion criteria.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed studies and extracted data. Disagreement in the selection of trials was resolved by consensus. Attempts were made to contact authors to verify accuracy of data.

MAIN RESULTS

Seven trials met the inclusion criteria (380 participants). Methodological quality was high. All studies recruited children with acute severe asthma and requiring hospital admission. Six studies sought participants who were unresponsive to nebulised short-acting beta-agonist and administered systemic steroids to study participants. In two studies where some children were able to perform spirometry, baseline FEV1 was between 35 and 45% predicted. The addition of aminophylline to steroids and beta2-agonist significantly improved FEV1% predicted over placebo at 6-8 hours, 12-18 hours and 24 hours. Aminophylline led to a greater improvement in PEF% predicted over placebo at 12-18 hours. There was no significant difference in length of hospital stay, symptoms, frequency of nebulsations and mechanical ventilation rates. There were insufficient data to permit aggregation for oxygenation and duration of supplemental oxygen therapy. Aminophylline led to a three-fold increase in the risk of vomiting. There was no significant difference between treatment groups with regard to hypokalaemia, headaches, tremour, seizures, arrhythmias and deaths.

AUTHORS' CONCLUSIONS

In children with a severe asthma exacerbation, the addition of intravenous aminophylline to beta2-agonists and glucocorticoids (with or without anticholinergics) improves lung function within 6 hours of treatment. However there is no apparent reduction in symptoms, number of nebulised treatment and length of hospital stay. There is insufficient evidence to assess the impact on oxygenation, PICU admission and mechanical ventilation. Aminophylline is associated with a significant increased risk of vomiting.

Intravenous aminophylline for acute severe asthma in children over 2 years using inhaled bronchodilators

BACKGROUND

Intravenous aminophylline was the bronchodilator of choice for many years until supplanted by more effective bronchodilators in the treatment of acute paediatric asthma. Recently there has been renewed interest in this therapy for children with acute severe asthma.

OBJECTIVES

To determine whether addition of intravenous aminophylline produces a beneficial effect in children with acute severe asthma receiving oxygen, maximised inhaled bronchodilators and oral/intravenous glucocorticoids.

SEARCH STRATEGY

The Cochrane Airways Group register of trials (based on MEDLINE, EMBASE, CINAHL and hand searched respiratory journals) and reference lists of relevant articles were used to identify relevant studies. The latest search was carried out in October 2000.

SELECTION CRITERIA

Only randomised-controlled trials comparing intravenous aminophylline with placebo in children treated with inhaled bronchodilators and systemic glucocorticoids for acute asthma were considered for this review.

DATA COLLECTION AND ANALYSIS

Full text of 35 trials were anonymized for author, date and publication and two blinded independent reviewers selected eligible studies for inclusion. Disagreement was resolved through consensus. Seven trials met the inclusion criteria. Attempts were made to contact authors to verify accuracy. Results were reported as weighted mean differences (WMD) or relative risk (RR) with 95% confidential intervals (CI).

MAIN RESULTS

Patients in these trials were predominantly school-aged children hospitalised for acute severe asthma with a baseline FEV1 at 35-40% of predicted and/or a baseline Pulmonary Index of 6-7. Aminophylline significantly improved percentage predicted FEV1 by 6 - 8 hours (WMD 8.4%; 95% CI: 0.82, 15.92%). The effect was maintained for 24 hours. Improvements were also seen in symptom scores at 6-8 hours (WMD= -0.71; 95% CI: -0.82,-0.60). There was no reduction in hospital stay or in number of nebulisers required. Vomiting was more likely with aminophylline therapy (Relative Risk = 3.69; 95% CI: 2.15, 6.33).

REVIEWER'S CONCLUSIONS

Addition of intravenous aminophylline should be considered early in the treatment of children hospitalised with acute severe asthma with sub optimal response to the initial inhaled bronchodilator therapy. Although the improvement is sustained for 24 hours, there is no apparent reduction in length of hospital stay or number of inhaled beta2-agonists nebulisations. Treatment with aminophylline is associated with an increased risk of vomiting.

Interaction between theophylline and mexiletine

Drugs influencing hepatic microsomal enzyme systems, such as mexiletine, may affect the elimination pattern of theophylline. The three patients reported here had a history of asthma and premature ventricular contractions, and were receiving theophylline therapy. A few days after starting the coadministration of mexiletine and theophylline, theophylline serum concentrations increased about twofold over concentrations during theophylline therapy. In one case, theophylline serum concentrations increased by 2.6 fold, and the patient developed nausea and anorexia. Mexiletine serum concentrations did not change. It seems that with mexiletine therapy, lower doses of theophylline may be required and careful monitoring of serum concentrations is necessary.

Effect of cimetidine on the pharmacokinetics of theophylline

1. The effect of the therapeutic doses of cimetidine (400 mg/twice daily) on theophylline metabolism in Jordanian volunteers was studied. 2. The administration of the above therapeutic cimetidine dose did not alter theophylline clearance and elimination half-life. 3. Cimetidine administration also failed to alter the elimination of theophylline metabolites in urine.

Zn(II)-theophylline-ethylenediamine: structure and pH stability

A zinc-containing salt of theophylline, Zn(II)-aminophylline, was synthesized and its structure determined by X-ray diffraction techniques. The zinc ion is coordinated to two theophylline anions and a molecule of ethylenediamine in a tetrahedral arrangement. The solubility of the compound in water at 30 degrees (0.047 mg/ml) is 180-fold lower than that of theophylline (8.40 mg/ml). The complex is relatively stable in the alkaline pH range, but it hydrolyzes, releasing theophylline in acidic environments. The rate of theophylline release is pH dependent. These properties are useful in formulating chewable tablets and liquid suspension dosage forms that overcome the characteristic bitter taste of theophylline, yet provide for efficacious treatment of diseases involving the respiratory tract.

Aminophylline therapy in children: guidelines for dosage

The oral dosage of aminophylline required for therapeutic "trough" serum theophylline levels was studied in 150 children, 16 months to 19 years old (mean 8.28 years). Dosage requirements tended to be higher for children under 10 years, but marked person-to-person variability in the relation of dose to serum level was seen at all ages. Individual patients generally maintained consistent serum levels when receiving unchanging doses, although intercurrent disease sometimes disrupted this relationship. Individualization of oral dosage based on frequent serum measurements is necessary to maintain theophylline levels in the therapeutic range and to avoid toxicity.