How enalapril works
Enalapril affects one of the most important systems in the human body for regulating blood pressure: the renin-angiotensin-aldosterone system (RAAS).
To maintain blood pressure, the enzyme renin is produced in the kidneys. It converts the protein angiotensinogen from the liver into the hormone precursor angiotensin I. In a second step, another enzyme – angiotensin-converting enzyme (ACE) – converts angiotensin I into the active hormone angiotensin II. This then causes a rise in blood pressure via various mechanisms, namely it ensures that:
- less water is excreted via the kidneys,
- small arterial vessels constrict, and
- the production of aldosterone is suppressed.
All together, this causes blood pressure to rise.
ACE inhibitors such as enalapril block ACE. As a result, less angiotensin II is produced – the blood pressure-increasing effects are reduced. This relieves the heart.
In addition to their blood pressure-lowering effect, ACE inhibitors also reduce unwanted enlargement (hypertrophy) of the heart. Such hypertrophy can occur, for example, due to the increased strain of high blood pressure or as a result of cardiac insufficiency.
Absorption, degradation and excretion
After ingestion, about two-thirds of enalapril is rapidly absorbed through the intestine into the blood, where it reaches peak levels after one hour. Absorption is not impeded by food.
In the blood, enalapril, which is actually an inactive precursor of the active ingredient enalaprilat, is first converted into it. The highest levels of the active form are found in the blood after about four hours. Excretion of enalapril and enalaprilat occurs via the kidneys in the urine.
When is enalapril used?
Enalapril is used to treat high blood pressure and heart failure (congestive heart failure) and to prevent heart failure if certain pre-existing conditions are present.
As a rule, enalapril must be taken on a long-term basis in order to permanently relieve the heart and blood vessels and thereby protect them.
How enalapril is used
Enalapril is taken in the form of tablets. Usually, a low dose is started, which is then slowly increased to the maintenance dose – if the enalapril dose is initially too high, a sharp drop in blood pressure with dizziness or even fainting may occur.
The tablet is taken once daily. In the case of very high dosages of 40 milligrams of enalapril (maximum daily dose), the administration should be divided between morning and evening.
What are the side effects of enalapril?
During treatment, blurred vision, dizziness, cough, nausea, and/or weakness occur in more than one in ten people treated.
Side effects that manifest in one in ten to one in one hundred patients include headache, depression, low blood pressure, heart arrhythmia, fast heartbeat, diarrhea, abdominal pain, skin rash, hypersensitivity reactions, fatigue, and increased potassium and creatinine blood levels.
Some of the side effects can be directly attributed to the lowered blood pressure caused by enalapril. Especially during the first period of treatment, normal blood pressure often feels subjectively too low.
Notify your doctor in case of cough, rash or hypersensitivity reactions. The medication may need to be changed.
What should I watch for while taking enalapril?
Contraindications
Enalapril should not be used in:
- angioneurotic edema in the past (special form of water retention in the tissue; also called Quincke’s edema)
- concomitant treatment with valsartan/sacubitril (drug for heart failure)
- Pregnancy in the second and third trimester
Interactions
Combined use of enalapril and potassium-sparing dehydrating agents (such as spironolactone, triamterene, amiloride) or potassium supplements may result in greatly increased potassium blood levels. Ciclosporin (immunosuppressant), heparin (anticoagulant), and cotrimoxazole (antibiotic) may also increase potassium levels in combination with enalapril.
Combination therapy with other antihypertensive drugs, often prescribed for severe hypertension, should always be staggered so that blood pressure does not drop too much at the beginning.
Alcohol enhances the blood pressure-lowering effect of enalapril. Dizziness, blurred vision, and falls may result.
Use of tricyclic antidepressants, neuroleptics (for psychotic symptoms such as hallucinations), and anesthesia medications may also result in an increased drop in blood pressure. Use of the mood stabilizer lithium should be monitored by blood level controls.
Taking painkillers and anti-inflammatory drugs from the group of non-steroidal anti-inflammatory drugs (NSAIDs) such as acetylsalicylic acid, ibuprofen or coxibe (selective COX-2 inhibitors) may weaken the effect of enalapril.
Certain drugs increase the risk of angioneurotic edema in combination with enalapril. These agents include racecadotril (anti-diarrheal agent) and vildagliptin (anti-diabetic agent).
Age Limitation
Enalapril is approved in children weighing 20 kilograms or more.
Pregnancy and breastfeeding
The use of enalapril in the first three months of pregnancy is not recommended for safety reasons – even though data from more than 6000 pregnancies did not indicate a risk of malformation in the first trimester.
Enalapril is strictly contraindicated in the second and third trimesters. The agents of choice for hypertension in this case are methyldopa and metoprolol.
Data on the use of enalapril in lactation are limited. Because the drug is unlikely to pass into breast milk, symptoms in the breastfed infant are unlikely. Nevertheless, enalapril is used in breastfeeding as a precaution only after better studied drugs have failed.
How to obtain medicines containing enalapril
Enalapril is available by prescription in Germany, Austria and Switzerland in any dosage.
Since when is enalapril known?
However, the active ingredient still had some unpleasant side effects such as skin rashes and taste disturbances. Just two years later, enalapril came onto the market as a direct competitor product. It has a better side effect spectrum.
