inhaled corticosteroid

An inhaled corticosteroid, or ICS, is the controller inhaler that calms the underlying inflammation in the airways. Unlike a rescue inhaler that quickly relaxes muscle, it works quietly in the background day after day, gradually settling the swelling and twitchiness that make airways prone to flare-ups.

Delivered straight into the lungs at low doses, the steroid suppresses the inflammatory cells and chemicals that drive asthma, reducing airway swelling and hyperreactivity over days to weeks. Because it is preventive, it must be taken regularly even when you feel well; it does little for a sudden attack. In asthma it is the cornerstone of treatment, and it is added in selected COPD patients, particularly those with frequent exacerbations or eosinophilic inflammation.

Inhaling the drug rather than swallowing it keeps doses low and largely confines the effect to the lungs, so serious whole-body steroid side effects are uncommon at usual doses. The main local nuisances are oral thrush and a hoarse voice, both reduced by using a spacer and rinsing the mouth after each dose.