No

Diagnostic Agent

Diagnosis of bronchial airway hyperactivity in subjects who do not have clinically apparent asthma

C

Concomitant use of beta-blockers; hypersensitivity to the drug; because of the potential for severe bronchoconstriction, methacholine challenge should not be performed on any patient with clinically apparent asthma, wheezing, or very low baseline pulmonary function tests (forced expiratory volume in one second less than 70% of predicted value).

Methacholine is a bronchoconstrictor for diagnostic purposes only. Perform inhalation challenge under the supervision of a physician trained in and thoroughly familiar with all aspects of the technique, all contraindications, warnings, and precautions of methacholine challenge and the management of respiratory distress. Have emergency equipment and medication immediately available to treat acute respiratory distress. Administer only by inhalation; severe bronchoconstriction and reduction in respiratory function can result. Patients with severe hyper-reactivity of the airways can experience bronchoconstriction at a dosage as low as 0.025 mg/mL (0.125 cumulative units). If severe bronchoconstriction occurs, reverse immediately by administration of a rapid-acting inhaled bronchodilator (beta-agonist).

<1%: Hypotension, complete heart block, substernal pain, tightness of the chest, syncope, headache, lightheadedness, throat irritation, itching, cough, dyspnea, wheezing

Store unreconstituted powder at 59°F to 86°F; store dilutions in refrigerator (36°F to 46°F) for up to 2 weeks

Methacholine chloride is a cholinergic (parasympathomimetic) synthetic analogue of acetylcholine. The drug stimulates muscarinic, postganglionic parasympathetic receptors, which results in smooth muscle contraction of the airways and increased tracheobronchial secretions.

Onset of action: Rapid

Peak effect: Within 1-4 minutes

Duration: 15-75 minutes or 5 minutes if the methacholine challenge is followed with a beta-agonist agent

Before inhalation challenge, perform baseline pulmonary function tests; the patient must have an FEV₁ of at least 70% of the predicted value. The following is a suggested schedule for administration of methacholine challenge. Calculate cumulative units by multiplying number of breaths by concentration given. Total cumulative units is the sum of cumulative units for each concentration given. (See breakdown below)

Serial concentration 0.025 mg/mL; No. of breaths 5; cumulative units per concentration 0.125; total cumulative units 0.125

Vial D:

Serial concentration 0.25 mg/mL; No. of breaths 5; cumulative units per concentration 1.25; total cumulative units 1.375

Vial C:

Serial concentration 2.5 mg/mL; No. of breaths 5; cumulative units per concentration 12.5; total cumulative units 13.88

Vial B:

Serial concentration 10 mg/mL; No. of breaths 5; cumulative units per concentration 50; total cumulative units 63.88

Vial A:

Serial concentration 25 mg/mL; No. of breaths 5; cumulative units per concentration 125; total cumulative units 188.88

Determine FEV₁ within 5 minutes of challenge, a postive challenge is a 20% reduction in FEV₁

Powder for reconstitution, inhalation, as chloride: 100 mg/5 mL