Angiotensin-converting enzyme (ACE) inhibitors are medications that help blood vessels to relax. ACE inhibitors help the body to reduce the production of Angiotensin II, a substance that narrows blood vessels and increases blood pressure, resulting in high blood pressure, or hypertension. ACE inhibitors have been alleged to exacerbate the asthma condition in asthmatic patients, but the exact relationship has not been verified yet.

A common side-effect of ACE inhibitors is to trigger dry, chronic coughs. A kind of respiratory activity, called ‘asthma equivalent’ has been known to cause this kind of cough. This means that the activities inside the respiratory system imitate that of asthma. Although serious effects of ACE inhibitors to people with asthma are uncommon, they have been reported. For this reason, ACE inhibitors are not used as the preferred drug with asthmatic patients.  For elderly patients, it is even more important to avoid ACE inhibitors as medications for high blood pressure and diabetes, as it can trigger or even worsen asthmatic condition in them.

Besides, any cough that can cause the stomach acid to flow back into the esophagus (reflux), can in turn facilitate the production of more cough and worsen asthma. Thus, any cough caused by ACE inhibitors should be reported immediately to a healthcare professional.