Current status of beta-adrenergic agonists in bronchial asthma

Drug therapy approaches in the treatment of acute severe asthma in hospitalised children

Acute severe paediatric asthma remains a serious and debilitating disease throughout the world. The incidence and mortality from asthma continue to increase. Early, effective and aggressive outpatient therapy is essential in reducing symptoms and preventing life-threatening progression. When complications occur or when the disease progresses to incipient respiratory failure, these children need to be managed in a continuous care facility where aggressive and potentially dangerous interventions can be safely instituted to reverse persistent bronchospasm. The primary drugs for acute severe asthma include oxygen, corticosteroids, salbutamol (albuterol) and anticholinergics. Second-line drugs include heliox, magnesium sulfate, ketamine and inhalational anaesthetics. Future therapies may include furosemide, leukotriene modifiers, antihistamines and phosphodiesterase inhibitors. This review attempts to explore the multitude of medications available with emphasis on pharmacology and pathophysiology.

Has asthma medication use in children become more frequent, more appropriate, or both?

OBJECTIVE

Despite national initiatives to improve asthma medical treatment, the appropriateness of physician prescribing for children with asthma remains unknown. This study measures trends and recent patterns in the pediatric use of medications approved for reversible obstructive airway disease (asthma medications).

DESIGN

Population-based longitudinal and cross-sectional analyses. Setting. A nonprofit staff model health maintenance organization located in the Puget Sound area of Washington state.

PARTICIPANTS

Children 0 to 17 years of age enrolled continuously during any one of the years from 1984 to 1993 (N = 83 232 in 1993). PRIMARY OUTCOME MEASURES. Percent of enrollees filling prescriptions for asthma medications and fill rates by medication class and estimated duration of inhaled antiinflammatory medication use.

RESULTS

Between 1984 and 1993, the frequency of asthma medication use increased: the percent of children filling any asthma medication prescription increased from 4. 0% to 8.1%, whereas the percent filling an inhaled antiinflammatory inhaler rose from 0.4% to 2.4%. In contrast, the intensity of inhaled antiinflammatory use decreased among users; 37% of users filled more than two inhalers during the year in 1984, and 29% in 1993. In high beta-agonist users (filling more than two beta-agonist inhalers each quarter per year), the estimated duration of inhaled antiinflammatory use increased slightly from a mean of 4.1 months per year in 1984-1986 to 5.0 months in 1991-1993; estimated duration of use in adolescents 10 to 17 years of age was approximately half that of children 5 to 9 years of age.

CONCLUSIONS

The proportion of children using asthma medications increased substantially during the study period, but the use of inhaled antiinflammatory medication per patient remained low even for those using large amounts of inhaled beta-agonists. These findings suggest that most asthma medications were used by children with mild lower airway symptoms and that inhaled antiinflammatory medication use in children with more severe disease fell short of national guidelines.

Comparison between epinephrine and terbutaline injections in the acute management of asthma

A randomized clinical trial comparing subcutaneous epinephrine and terbutaline injections was conducted in asthmatic children at The Methodist Hospital, Brooklyn, New York. Clinical evaluation using the Asthma Scoring System was done at baseline and serially, every 15 minutes, following injection of either drug. Reversal of wheezing, and changes in respiratory and heart rates were assessed using strict a priori criteria. The patients' differential response to both drugs was assessed by a crossover study when the same patients came subsequently for another episode of wheezing. Our results show terbutaline to be more efficacious at a dose comparable to epinephrine dose.

Protective effect of tulobuterol on methacholine-induced bronchospasm in asthmatic children

In a single-blind, placebo-controlled trial 19 asthmatic children aged 10-14 years were studied during a stable phase of the disease. All patients were tested with a methacholine inhalation test on two consecutive days, on the first day after oral administration of a placebo, and on the second day following an oral dose of tulobuterol HCl. The cumulative methacholine dose required to produce at least a 20% decrease in FEV1 was significantly higher after tulobuterol than after the placebo. It is concluded that tulobuterol HCl reduces methacholine-induced bronchospasm in children.

Oxygen desaturation in adults following inhaled metaproterenol therapy

Following bronchodilator therapy in asthmatic patients, a fall in arterial oxygen tension (PaO2) has been attributed to increased perfusion of persistently underventilated alveoli. We used continuous noninvasive pulse oximetry to evaluate the extent and timing of oxygen saturation (SaO2) decrease in adults following metaproterenol inhalation for acute bronchospasm. We also examined the effect of supplemental oxygen upon these factors. Baseline and peak drop in SaO2 after completion of the first bronchodilator therapy were measured and the percent change in SaO2 was calculated. A total of 47 patient visits were studied; 10 patients received supplemental oxygen. Mean age was 38 +/- 17.9 years. Baseline was SaO2 = 94.6 +/- 2.9%, peak drop SaO2 = 91.4 +/- 3.4%, and percent change in SaO2 = -3.4 +/- 2.5%. The mean time to peak drop was 24.4 +/- 15.4 minutes in the 40 patients, with an observed drop after initial treatment. The absolute change in SaO2 from baseline was significant both with and without oxygen (P less than .05 and less than .01, respectively). The group receiving oxygen had a significantly smaller percent drop and a larger proportion of patients showing no drop in SaO2 (P less than 0.01 and less than 0.03, respectively). Clinically significant oxygen desaturation can occur within 30 minutes of inhaled bronchodilator therapy. Supplemental oxygen (2-3 L/min) helps blunt the metaproterenol-induced drop in SaO2.

The effects of long-term infusion of salbutamol, diltiazem and nifedipine on uterine contractions in the ovariectomized, post-partum rat

The sensitivity of the uterus to the inhibition of contractions by salbutamol, diltiazem or nifedipine was assessed in the ovariectomized, post-partum rat by dose-response curves following bolus intravenous (i.v.) administration. These tests were performed before (day 1), immediately after a 20 h i.v. infusion of salbutamol, diltiazem, nifedipine or appropriate control infusate (day 2) and after a further 20 h infusion of saline (day 3). In a further group of animals sensitivity to nifedipine was assessed before and after a 20 h infusion of salbutamol. Uterine contractions were monitored throughout infusions. Infusion of salbutamol (2 micrograms kg-1 min-1) produced an initial marked inhibition of uterine contractions, an effect which was not maintained despite continued infusion. Contractions reappeared after 2 h of infusion and reached pre-infusion levels by 5 h. The dose-response curve to salbutamol on day 2 was shifted more than 100 fold to the right compared with that on day 1. Sensitivity of the uterus on day 3 did not differ from that on day 1. Nifedipine (25 micrograms kg-1 min-1) produced sustained inhibition of uterine contractions throughout the 20 h of infusion. Sensitivity of the uterus to nifedipine could not, therefore, be tested on day 2; sensitivity on day 3 did not differ from that on day 1. In addition, there was no change in sensitivity of the uterus to nifedipine after a 20 h infusion of salbutamol. 4 Diltiazem (200 Ig kg-' min-') produced a marked initial inhibition of uterine contractions, with a partial return of contractions during continued infusion in 7 out of 12 animals so that mean integral values reached 40% of those pre-infusion. The dose-response curve to diltiazem on day 2 showed a 25 fold shift to the right compared with that on day 1 in 4 out of 12 animals where the test could be performed. Sensitivity of the uterus on day 3 did not differ from that on day 1. 5 These findings suggest that marked but reversible tolerance to the inhibitory actions of salbutamol on uterine contractions occurs during long-term infusion. There was no evidence of tolerance to the uterine actions of nifedipine, but there was evidence of tolerance to diltiazem in some animals.

Arterial oxygen desaturation following salbutamol inhalation in acute asthma

The practicality and accuracy of a new ear oximeter was evaluated. The SaO2 measured with this instrument correlated significantly with simultaneous SaO2 measurements with another ear oximeter in 12 children (age three months to 20 years) with chronic pulmonary or cardiac diseases (r = 0.93, p less than 0.001), and also correlated significantly (r = 0.96, p less than 0.001) with calculated SaO2 based on blood gas measurements of blood from the left side of the heart obtained during cardiac catheterization. The SaO2 was then measured continuously and readings were taken before and five, 15, and 30 minutes after salbutamol inhalation by face mask in 18 children. Following treatment, mean PEFR increased significantly, and mean SaO2 was significantly lower than preinhalation values at five and 15 minutes postinhalation. At 30 minutes, SaO2 had returned to control values. In nine of 18 subjects, SaO2 fell greater than or equal to 5 percent. This response was not predictable on the basis of different parameters (treatment, heart rate, PEFR). The findings suggest that supplemental O2 may be required during the first 30 minutes posttreatment.