Effect of theophylline on respiratory neuromuscular drive

Acute action of aminophylline in patients with amyotrophic lateral sclerosis

OBJECTIVE

This study investigated whether aminophylline has an acute effect on the muscle performance of patients with amyotrophic lateral sclerosis (ALS). The study was a randomized, double-blind, crossover against placebo.

MATERIALS AND METHODS

Twenty-five patients (48.5 +/- 14.1 years) with ALS were evaluated by means of forced vital capacity (FVC), maximal mouth inspiratory and expiratory pressures (P(Imax)/P(Emax)) and endurance, maximum voluntary ventilation (MVV) and handgrip strength (HS); variables were measured before and after the patients received an intravenous infusion of aminophylline or placebo.

RESULTS

MVV (P<0.02) and HS of the right and left hands (P=0.05) increased after aminophylline infusion. There was a positive correlation between FVC and P(Imax) (r=0.80; P<0.05); between MVV and P(Imax) post-aminophylline, respectively (r=0.77; P<0.05). Serum aminophylline levels ranged from 5.3 to 10.5 microg/mL (mean 7.30).

CONCLUSION

The acute administration of aminophylline improves the endurance of respiratory muscles and increases handgrip strength in patients with ALS.

Use of theophylline in chronic obstructive pulmonary disease: examining the evidence

PURPOSE OF REVIEW

The role of theophylline in the management of chronic obstructive pulmonary disease remains controversial. This review was undertaken to determine the efficacy of theophylline in patients with stable disease.

RECENT FINDINGS

Twenty-two good quality randomized controlled trials were included in this systematic review. The review showed that theophylline significantly improved forced expiratory volume in 1 s and forced vital capacity (weighted mean difference 0.10 L; 95% confidence interval 0.04-0.16 and weighted mean difference 0.21 L; 95% confidence interval 0.10-0.31, respectively). V also improved with theophylline (weighted mean difference 195.27 mL/min; 95% confidence interval 112.71-277.83), as did Pa and Pa (weighted mean difference 1.45 mmHg; 95% confidence interval 0.26-2.65 and weighted mean difference -1.09 mmHg; 95% confidence interval -1.83 to -0.35, respectively). Patients preferred theophylline over placebo (relative risk 2.27; 95% confidence interval 1.26-4.11). Theophylline increased the risk of nausea, however, compared with placebo (relative risk 7.67; 95% confidence interval 1.47-39.94).

SUMMARY

This review has shown that oral theophylline plays an important role in the management of patients with stable chronic obstructive pulmonary disease by improving lung function, arterial blood gas tensions and ventilatory capacity. Patients also preferred treatment with theophylline when compared with placebo. The benefits of theophylline in stable chronic obstructive pulmonary disease, however, have to be weighed against the risk of adverse effects, particularly nausea.

Efficacy of theophylline in people with stable chronic obstructive pulmonary disease: a systematic review and meta-analysis

OBJECTIVES

To determine the efficacy of oral theophylline compared with placebo in people with stable chronic obstructive pulmonary disease (COPD).

METHODS

Systematic review of randomized-controlled trials comparing oral theophylline with placebo for a minimum of 7 days in people with stable COPD.

RESULTS

Twenty randomized-controlled trials were included in this review. The following outcomes showed significant improvement with theophylline compared with placebo: FEV1 and FVC both improved with theophylline (weighted mean difference [WMD] 0.10 L; 95% confidence interval [95% CI] 0.04-0.16 and WMD 0.21 L; 95% CI 0.10-0.32, respectively). VO2 max also improved with theophylline (WMD 195.27mL/ min; 95% CI 112.71-277.83), as did PaO2 and PaCO2 (WMD 3.18 mmHg; 95% CI 1.23-5.13 and WMD -2.36mmHg; 95% CI -3.52 to -1.21, respectively). Patients preferred theophylline over placebo (relative risk 2.27; 95% CI 1.26-4.11). Theophylline increased the risk of nausea compared with placebo (RR 7.67; 95% CI 1.47-39.94).

CONCLUSION

This review has shown that theophylline still has a role in the management of stable COPD, and is preferred by patients over placebo. However, the benefits of theophylline in stable COPD have to be weighed against the risk of adverse effects.

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.

Assessment and management of dyspnoea

The terms 'dyspnoea' or 'breathlessness' refer to an individual's subjective awareness of discomfort related to the act of breathing. Elevations in CO2 above normal levels have been shown to cause breathlessness although it is unlikely to be the sole cause of breathlessness in a clinical setting. Several studies suggest that supplemental O2 during exercise will diminish the sensation of breathlessness although not all work has confirmed this finding. Much about the role of gas exchange in dyspnogenesis remains controversial. Phrenic blockade can abolish dyspnoea in response to breath-holding, while work in quadriplegics suggests that the intercostal muscles are not involved. A separate and direct pathway from the respiratory centre to the sensory cortex has also be implicated. Threshold discrimination has established that patients with chronic airflow limitation (CAL) have a blunted response to the addition of resistive loads to breathing, while category scaling methods (e.g. the Borg scale) have added descriptive terms to these physiological measures. Questionnaires often appear limited by their subjectivity and lack of correlation with physiological changes, but remain a useful tool in the clinical setting. In regard to therapy of dyspnoea high fat diets have a theoretical advantage in the CAL group but are generally not well tolerated. Resistive training devices and exercise training in CAL have been widely researched but in general, measures of lung remain unaltered and many of the studies would suggest that they have little, if any, inpact on functional status. Beta-agonists have been widely shown to be useful in CAL patients, despite the fact that bronchodilatation is not always demonstrable. Anticholinergics have be shown to be effective bronchodilators, but whether there is an improvement in dyspnoea above that expected from improvement in lung function is unclear. Animal studies and work in normal individuals would suggest that methylxanthines have a theoretical role in CAL possibly by increasing diaphragmatic muscle strength and decaying fatigue, but toxicity and lack of clear benefit in this group suggest that they should not be used as monotherapy. There is little evidence to support the use of opioids in chronic CAL although their role in the acute dyspnoea of end-stage CAL remains defined. The use of benzodiazepines has also been disappointing. Bullectomy remains widely accepted in clinical practice. New techniques such as 'reduction surgery' for diffuse emphysema are showing promise, although still in need of further testing and validation.

Effect of theophylline on exercise performance in patients with severe chronic obstructive pulmonary disease

BACKGROUND

Theophylline is a well known bronchodilator which has been used for more than 50 years in the treatment of obstructive pulmonary diseases. In patients with severe chronic obstructive pulmonary disease whose cardiopulmonary performance is limited by their ventilatory capacity the administration of theophylline may improve exercise performance.

METHODS

A randomised, placebo controlled, double blind, crossover trial was conducted in 22 patients with severe but stable disease. The patients (mean age 68 years) were studied before and after one month of placebo and one month of treatment with a sustained release preparation of theophylline administered orally. The theophylline dose was adjusted until a blood level above 55.5 mumol/l was achieved. The two treatments were administered in random order and separated by a two week washout period. After theophylline was administered for one month a mean level of 68.2 mumol/l was achieved. Pulmonary function tests, arterial blood gas measurements, maximal voluntary ventilation (MVV), and an incremental exercise test were performed before (baseline) and at the end of the first and second month of treatment.

RESULTS

Pulmonary function tests showed no improvement in the flow parameters but showed an improvement in MVV after treatment with theophylline. Pulmonary gas exchange was improved after theophylline (resting arterial PO2 8.91 v 8.59 kPa, PCO2 5.38 v 5.56 kPa). The incremental exercise study showed improvement in maximal work rate (86.5 v 75.0 watts) and maximal ventilation (VEmax) (46.7 v 43.01/min). The dyspnoea index on maximal effort (VEmax/MVV), anaerobic threshold, and oxygen pulse remained unchanged. Resting and exercise heart rate were higher after theophylline.

CONCLUSIONS

Theophylline improved cardiorespiratory performance in these patients with severe chronic obstructive pulmonary disease mainly by increasing the ventilatory capacity.

Serum doxapram and respiratory neuromuscular drive in normal man

To investigate the means by which doxapram affects the control of ventilation, ventilatory function and P0.1 have been related to serum doxapram concentration during a 45-min infusion of doxapram hydrochloride in 7 healthy, conscious subjects under normoxic conditions. Serum doxapram concentrations increased during the infusion: 1.88, 2.48, 3.42, and 3.97 micrograms/ml after 5, 10, 30 and 45 min, respectively. The majority of significant changes in the measurements from the baseline were observed at 30 and 45 min: VE, VT, P0.1, P0.1/end-tidal CO2 tension, VT/Ti and blood pressure were increased, and end-tidal CO2 tension was decreased. No significant changes in Pdimax, Ti/Ttot, VE/P0.1, and P0.1/(VT/Ti) were observed. A correlation was observed between the % increases in P0.1 and VE and doxapram concentration, and between VE and P0.1. The doxapram-induced increase in VE appears to be caused by increased neural drive. It is related to the serum drug concentration in the conscious subject.