Bronchoprotective effect of vilanterol against methacholine-induced bronchoconstriction in mild asthmatics: A randomized three-way crossover study

Short-term effect of once-daily fluticasone furoate on methacholine-induced bronchoconstriction in mild asthmatics

BACKGROUND

Inhaled corticosteroids (ICS) decrease airway inflammation and airway hyperresponsiveness (AHR). Previous studies have generally investigated the effect of ICS on methacholine-induced AHR following weeks or months of medium to high dose treatment.

PURPOSE

The short-term effects of once-daily fluticasone furoate (FF) 100 mcg on methacholine-induced AHR and airway inflammation were examined over the course of one week.

METHODS

Eleven mild asthmatics completed this randomized, double-blind crossover study. Once-daily FF (100 mcg) and identical appearing placebo Ellipta® inhalers were given for 7 days with a 2-week washout. Methacholine challenges were performed before and 24 h after the first, third and seventh doses. Fractional exhaled nitric oxide (FeNO) was measured initially and at 7 days.

RESULTS

FF significantly (p = 0.0009-0.0078) increased methacholine PD₂₀ (provocative dose causing 20% fall in forced expiratory volume in 1 s) at all times. Doubling dose shifts (95% CI) were 1.23 (0.60-1.86), 1.17 (0.68-1.67) and 1.44 (0.93-1.94) after the first, third and seventh dose respectively. FeNO (geometric mean, 95% CI) decreased significantly (p = 0.0049) following FF treatment from 37.9 ppb (23.7-60.5) initially to 22.9 ppb (14.8-35.5) at 7 days. Placebo did not affect methacholine PD₂₀ or FeNO.

CONCLUSION

Single-dose FF 100 mcg decreased methacholine AHR at 24 h without significant further improvement with continued daily use over 7 days. The inhibition in AHR after one week of daily dosing coincided with a significant decrease in FeNO at 7 days. Contrary to past assumptions, the ICS FF appears to rapidly reduce AHR to methacholine.

Ultra-LABAs for the treatment of asthma

The term ultra-LABA indicates once-daily β2-AR agonists (abediterol, indacaterol, olodaterol and vilanterol) that are single enantiomers of the (R)-configuration. All have a near full-agonist profile at human β2-AR. They can be prescribed in asthmatics only when associated with an with ICS, although further confirmations need to clarify what really these agents add if used in association to ICS and in what asthmatic patients this association may have more value. They are also under development in triple inhalers that include an ultra-LABA, a LAMA and an ICS. The once-daily posology might increase adherence in long-term treatment of asthma but superiority to twice-daily LABAs has not yet been fully demonstrated. In any case, still no ultra-LABA can be recommended as preferred.

Direct bronchoprovocation test methods: history 1945-2018

INTRODUCTION

Bronchoprovocation inhalation challenge tests with direct acting stimuli (e.g. methacholine) are widely used clinically to aid in the diagnosis of asthma. Areas covered: The history of direct challenges with histamine and muscarinic agonists is reviewed. This began with parenteral administration of stimuli with responses monitored clinically and by VC, progressing to inhalation dose-response challenges monitored by FEV₁ and FEV₁/VC ratio, both (the challenge method and the technology to measure FEV₁) developed by Robert Tiffeneau in the mid-1940s. Careful standardization of methods has become appreciated albeit after-the-fact. Recent guidelines recommend standardizing the methacholine PD₂₀ at 400 μg above which a methacholine challenge is considered negative.

CONCLUSIONS

The methacholine inhalation test is highly sensitive for a diagnosis of current asthma when symptoms under evaluation are clinically current and when methacholine is inhaled without deep inhalations. Under these circumstances, a methacholine PD₂₀ > 400 μg excludes current asthma with reasonable certainty. PD₂₀ values >25 μg and ≤400 μg will have a variable specificity and positive predictive value for asthma which increases the lower the PD₂₀ and the higher the pre-test probability for a diagnosis of asthma. A PD₂₀ ≤25 μg has high specificity and low sensitivity for asthma.