ACE inhibitors, an acronym for angiotensin converting enzyme inhibitor, are a class of medicines used to treat high blood pressure (hypertension). They work by blocking or inhibiting an enzyme in the body that facilitates the production of a substance called angiotensin. This substance has powerful effects in causing blood vessels to tighten. By preventing angiotensin from exerting its effect, the blood vessels become more relaxed and consequently blood pressure is lowered. As an analogy, it is like relaxing the nozzle of a water hose, thereby lowering the water pressure. Here, the water hose represents blood vessels and water represents blood.

IS ACE INHIBITOR APPROPRIATE FOR ME?
All medicines are like double-edged swords. There are risks of side effects besides their medicinal benefits. The doctor will have to make his or her decision based on the benefits that will be derived versus potential side effects in susceptible individuals. The aim is to maximise benefits while minimising risks and there are various classes of blood pressure-lowering medicines to suit different individuals.

PROPER USE OF ACE INHIBITORS
It is important to take blood pressure control medicines like ACE Inhibitors as instructed continuously until otherwise directed. One should not stop taking the prescribed dose even after blood pressure has normalized. This is because in order for the blood pressure to remain normalized, continuous intake of the medicine is necessary. It is like maintaining a hold on the nozzle of a water hose to maintain the required pressure.

High blood pressure is a chronic condition unlike acute conditions like bacterial infections where antibiotics are taken for a limited time frame. ACE inhibitors are used for long term control of blood pressure in order to avoid secondary complications like heart failure, blood vessel disease, stroke, or kidney disease and are not used to cure the condition.

SOME COMMON SIDE EFFECTS OF ACE INHIBITORS
A commonly reported side effect of ACE inhibitors is coughing. It is not dangerous in itself but may be annoying to some. Some people may experience some minor headaches.

While the above are minor side effects, some individuals may experience side effects which may have serious implications. One would be well advised to check with the doctor immediately if there is any fever and chills, swelling of face, mouth, hands, or feet, trouble in swallowing or breathing or irregular heartbeat after taking this medicine.

ARE ALL ACE INHIBITORS THE SAME?
The different members in this class of medicine have differing properties. They are different in their onset and duration of action, the way they are eliminated from the body as well the dosing schedule, to name a few. The newer ones are dosed at once daily regimes making them more convenient to take as a routine.

OTHER USES OF ACE INHIBITORS
Besides being used as a blood pressure-lowering agent, some ACE inhibitors are preferred in patients who have had suffered a heart attack to slow down the weakening of the heart and improve survival rates. Certain ACE inhibitors have been shown to have a protective effect on the kidneys and had been used in hypertensive patients with diabetes and related kidney problems. In addition, some members of this group of medicines have been used to manage congestive heart failure or even for other conditions as elucidated by well-controlled studies and deemed fit by the doctor.

So, while there is a lot of attention on this class of medicine, the cards are primarily in the doctor's hands to prescribe as necessary and befitting the situation.

(This article first appeared in Parkway Medicine, April 2002)