Effect of Vilanterol on Methacholine Challenge Results

This will be a double-blind, three-way crossover study comparing combination vilanterol+fluticasone with fluticasone monotherapy and a placebo (vilanterol is not available as a monotherapy). The order in which the treatments are given will be randomized and each treatment will be separated by a minimum one-week washout. Fifteen asthmatic participants will be recruited from the local community. Methacholine challenge testing (MCT) with the two-minute tidal breathing protocol will be used to quantify the bronchoprotective effects (if any) of each treatment against methacholine-induced bronchoconstriction.

Each participant will undergo a total of nine methacholine challenges. After a baseline methacholine challenge, the randomized treatment (identity unknown to investigator or participant) will be administered through an Ellipta® (multi-dose dry powder inhaler). Thirty minutes following treatment administration, a second methacholine challenge will be performed. At 24 hours post-treatment, each participant must re-visit the lab for one methacholine challenge. The same process will be followed for each treatment.

Inclusion criteria

• men and women aged 18 or older
• stable mild-to-moderate asthma
• baseline methacholine PC20 less than or equal to 8mg/mL
• FEV1 greater than or equal to 65% of predicted

Exclusion criteria

• Use of long-acting anticholinergic or long-acting beta2 agonist within 30 days of study
• pregnant or nursing
• diabetes
• hypokalemia
• cardiovascular, prostate, kidney, or urinary retention problems
• lactose-intolerant
• allergy-induced asthma symptoms or upper respiratory tract infection within four weeks of study
• current smokers
• past smokers with smoking history >10 pack years