Metacolina Lofarma (Methacholine Chloride)

Methacholine chloride is used in respiratory diagnostic testing to evaluate airway hyperresponsiveness.

• Bronchial challenge test for asthma diagnosis: provokes controlled bronchoconstriction to assess airway hyperresponsiveness.
• Evaluation of suspected asthma in adults: helps differentiate asthma from other respiratory conditions.
• Research studies of airway physiology: provides a standardized agent for experimental bronchial provocation.

• Methacholine chloride acts as a direct muscarinic (M3) receptor agonist on airway smooth‑muscle cells. Binding to these receptors triggers intracellular calcium release, causing contraction of the bronchial smooth muscle and resulting in a measurable decrease in airflow, which is used to assess airway hyperreactivity during diagnostic testing.

Methacholine chloride may cause several adverse reactions during bronchial challenge testing.

Common Side Effects

• Cough: transient irritation of the airway.
• Throat irritation: mild discomfort after inhalation.
• Transient wheezing: short‑lasting airway narrowing.
• Mild dyspnea: temporary shortness of breath.
• Headache: occasional post‑procedure symptom.
• Nausea: mild gastrointestinal upset.

Serious or Rare Side Effects

• Severe bronchospasm: marked airway constriction requiring emergency treatment.
• Hypoxemia: significant drop in blood oxygen levels.
• Cardiac arrhythmias: irregular heart rhythms in susceptible individuals.
• Anaphylaxis: rare systemic allergic reaction.
• Pulmonary edema: fluid accumulation in lungs.
• Persistent respiratory distress: prolonged difficulty breathing after the test.

When using methacholine chloride for bronchial challenge testing, several safety measures are essential.

• Patient selection: avoid in individuals with severe obstructive lung disease.
• Baseline lung function: perform spirometry before the test to establish reference values.
• Rescue medication: have a short‑acting bronchodilator readily available.
• Monitoring: observe the patient continuously during and after administration.
• Contraindications: do not use in patients with known hypersensitivity to methacholine or related compounds.
• Store at room temperature: keep in the original container, protect from light and moisture.

Methacholine chloride can interact with other medications that affect airway tone or bronchial reactivity.

Major Interactions (Avoid)

• Beta‑agonists: may blunt the bronchoconstrictive response, reducing test sensitivity.
• Anticholinergics: may inhibit methacholine effect, leading to false‑negative results.
• MAO inhibitors: potential for exaggerated bronchospasm.

Moderate Interactions (Monitor Closely)

• Corticosteroids: may reduce airway reactivity, requiring interpretation adjustment.
• Theophylline: may modify response; monitor lung function closely.
• ACE inhibitors: can increase cough, potentially confounding test results.