Tianqingsuxin Methacholine Chloride Powder for Solution, for Inhalation

1. Indications and Usage
Bronchial Hyperresponsiveness: Indicated for the methacholine challenge test to diagnose bronchial hyperresponsiveness in adult patients without clinically significant asthma symptoms and in children aged 5 years and older who can cooperate well.
Diagnostic Restriction: Not recommended for use in patients with clinically significant asthma or wheezing.
2. Dosage and Administration
Route of Administration: For Inhalation ONLY. The powder must be reconstituted and diluted with 0.9% Sodium Chloride Injection.
Administration Protocol: The methacholine challenge test should be conducted under the supervision of a physician trained in challenge test techniques and management of respiratory distress.
Dosing Method: Patients inhale prepared dilute solutions via a nebulizer, starting from low concentrations and progressively increasing until a positive result is obtained or the maximum concentration is reached.
Critical Administration Instructions:
Emergency Readiness: Emergency equipment and drugs for acute respiratory distress must be readily available.
Reversal: If severe bronchoconstriction occurs, immediate administration of a short-acting inhaled beta2-agonist is required to reverse the constriction.
Baseline Measurement: Baseline pulmonary function testing (specifically FEV1) must be performed using 0.9% Sodium Chloride Injection prior to administration.
3. Mechanism of Action
Receptor Agonism: Methacholine is a cholinergic agonist that directly stimulates muscarinic receptors on airway smooth muscle cells.
Bronchoconstriction: Activation of these receptors enhances vagal nerve stimulation, leading to bronchial smooth muscle contraction and increased bronchial secretions.
Diagnostic Utility: In patients with hyperresponsive airways, this results in a significant reduction in forced expiratory volume (FEV1), confirming airway hyperresponsiveness.
4. Safety and Warnings
Severe Bronchoconstriction: Administration may cause severe bronchoconstriction (including at the lowest dose).
Absolute Contraindication: Contraindicated in patients with a baseline FEV1 <60% of predicted value (children and adults) or FEV1 <1.5 L (adults).
Asthma Restriction: Not recommended for patients with clinically significant asthma or wheezing due to the high risk of severe adverse respiratory events.
Emergency Preparedness: Immediate availability of resuscitation equipment and short-acting beta2-agonists is mandatory during testing.
5. Adverse Reactions and Clinical Research
Most Common Adverse Reactions: Bronchospasm (including chest tightness, cough, or wheezing).
Other Adverse Reactions: Headache, throat irritation, dizziness, and pruritus.
Clinical Research Highlights: Methacholine challenge testing is a highly sensitive and standard clinical tool for evaluating airway hyperresponsiveness, particularly in diagnosing asthma in patients with equivocal spirometry results.
6. Drug Interactions
Beta-Blockers: May interfere with the ability to reverse methacholine-induced bronchoconstriction.
Bronchodilators and Anticholinergics: Beta2-agonists, anticholinergics, and theophylline suppress the airway response to methacholine. These medications must be withheld for specific periods prior to testing (e.g., Short-acting beta2-agonists: 6 hours; Long-acting beta2-agonists: 36 hours; Short-acting anticholinergics: 12 hours; Long-acting anticholinergics: ≥168 hours; Oral theophylline: 12-48 hours).
Corticosteroids: Regular use of oral or inhaled corticosteroids may significantly reduce the airway response to methacholine.
7. Pharmaceutical Information
Chemical Composition: Active Ingredient: Methacholine Chloride.
Appearance: White or off-white crystalline powder.
Packaging: Available in single-use vials (e.g., 100 mg/vial).
Storage: Store in a tightly closed container, protected from light and moisture.