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Prolonged asthmatic responses to inhaled methacholine.
The Journal of Allergy and Clinical Immunology
|April 1, 1983
Summary
High doses of methacholine can trigger prolonged asthma attacks in some individuals, even after atropine pretreatment. The exact cause of these extended asthmatic responses remains unclear, warranting further investigation into asthma mechanisms.
Area of Science:
- Pulmonary Medicine
- Respiratory Pharmacology
Background:
- Asthma is a chronic respiratory disease characterized by airway inflammation and hyperresponsiveness.
- Anticholinergic agents like atropine and cholinergic agonists like methacholine are used to study airway function and reactivity.
Purpose of the Study:
- To investigate the pattern of asthmatic responses following inhaled atropine and methacholine in adult asthmatics.
- To determine if high-dose methacholine challenges after atropine can induce prolonged asthmatic responses.
Main Methods:
- Six adult asthmatic subjects inhaled atropine followed by increasing concentrations of methacholine.
- Methacholine's provocative concentration (PC20) causing a 20% fall in forced expiratory volume in 1 second (FEV1) was measured.
- Prolonged asthmatic responses were monitored for up to 7 hours post-inhalation.
Main Results:
- Atropine pretreatment significantly increased the methacholine provocative concentration (PC20 FEV1) from 0.66 to 94.90 mg/ml.
- Four out of six subjects developed prolonged asthmatic responses after inhaling high-dose methacholine.
- These prolonged responses occurred at methacholine concentrations higher than clinical doses and were not directly dose-related.
Conclusions:
- Inhaled high-dose methacholine after atropine can induce prolonged asthmatic responses in susceptible individuals.
- The mechanism underlying these prolonged asthmatic responses is not fully understood and requires further research.
- Cromolyn sodium did not prevent the prolonged response in one tested subject, suggesting a non-IgE mediated pathway.
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