bronchodilator
Meaning of bronchodilator: A medicine that relaxes the muscle squeezing the airways, so a narrowed breathing tube opens up again.
Definition of bronchodilator
A bronchodilator is a medicine that relaxes the band of muscle wrapped around the airways, widening them so air moves more freely. It relieves the wheeze, cough and chest tightness of asthma and chronic obstructive pulmonary disease. Most are inhaled, which delivers the drug straight into the lungs and keeps the amount reaching the rest of the body small.
How does an airway narrow?
Each small airway is wrapped in a ring of smooth muscle. When that muscle tightens, the tube narrows and air has to squeeze through, which produces the whistling sound of a wheeze. Pushing air out is harder than drawing it in, so the chest feels tight and overfull. Two other changes narrow airways at the same time: the lining swells, and mucus collects in the channel. A bronchodilator addresses only the muscle. It does nothing about swelling, which is why anti-inflammatory inhalers are used alongside it in asthma rather than in place of it.
What are the main kinds?
| Class | How it acts | Timing |
|---|---|---|
| Beta-2 agonist | Signals the muscle to relax | Short-acting and long-acting forms |
| Antimuscarinic | Blocks the nerve signal that tightens the muscle | Short-acting and long-acting forms |
| Theophylline | Relaxes the muscle by a separate route | Taken by mouth, needs blood level checks |
What separates a reliever from a preventer?
A short-acting bronchodilator works within minutes and lasts a few hours. It is the reliever, taken when symptoms appear. A long-acting one works for twelve hours or more and is taken on a schedule to keep the airways open, not to rescue an attack in progress. How often the reliever is needed is itself a measure of control, so that frequency is tracked at every review. In emphysema and other forms of chronic obstructive lung disease, long-acting inhalers form the backbone of daily treatment, frequently combining two classes in a single device.
What side effects do they cause?
Beta-2 agonists can produce a fine tremor of the hands, palpitations and a jittery feeling, because the receptors they act on also exist in skeletal muscle and heart tissue. Large doses can lower blood potassium. Antimuscarinic inhalers commonly cause a dry mouth. Inhaled delivery keeps all of these far smaller than they would be from a tablet, and using a spacer with a pressurized inhaler puts more of the dose into the lungs and less into the throat.
Used in a sentence
The patient was reviewed after a rise in bronchodilator use over the preceding month.
Good to know
A bronchodilator opens the airway muscle but does nothing about the inflammation and mucus that also narrow it, so rising reliever use is treated as a marker of uncontrolled disease.
Word origin
Where “bronchodilator” comes from
Broncho- comes from the Greek bronchos, meaning windpipe; dilator comes from the Latin dilatare, to widen.