How carvedilol works
Carvedilol acts as both a beta and alpha blocker, relieving the heart in two ways:
- As a beta-blocker, it occupies the beta-1 receptors (docking sites) of the heart so that stress hormones can no longer dock there and cause the heart to beat rapidly. This allows the heart to beat at a normal pace again, which subsequently lowers blood pressure.
- As an alpha blocker, carvedilol also inhibits the alpha-1 receptors found in the blood vessels, where adrenaline would otherwise cause constriction to cause a rise in blood pressure. The active ingredient therefore ensures that the vessels relax. The heart then has to pump against a lower resistance, which protects it.
When the human body is under stress and has to perform at a high level, stress hormones such as adrenaline and noradrenaline are released into the blood by the adrenal glands. They bind to certain receptors in the target organs, setting them up for high performance:
Thus, the release of these hormones causes the heart to beat faster and blood pressure to rise due to a constriction of the vessels. The bronchioles (fine airway branches in the lungs) widen to take in more oxygen. Fat breakdown for energy is also stimulated and digestion is minimized so as not to waste energy on this.
Absorption, degradation and excretion
Carvedilol is rapidly absorbed in the intestine after ingestion by mouth. After about one hour, the highest levels are reached in the blood.
The active ingredient is metabolized mainly in the liver to inactive breakdown products, which are then excreted in the stool with the bile. After about six to ten hours, half of the absorbed amount of carvedilol has left the body in this way.
When is carvedilol used?
Carvedilol is used for diseases of the cardiovascular system such as:
- stable, chronic heart failure (congestive heart failure)
- stable, chronic angina (angina pectoris)
- essential (or primary) high blood pressure (hypertension), i.e. high blood pressure without any detectable underlying disease
Since therapy with carvedilol only combats the symptoms and not the causes of the diseases, use must be long-term.
How carvedilol is used
Carvedilol is used in the form of tablets. These are available in different dosages, as the therapy should be “gradual” – i.e. it is started with a very low dose, which is then slowly increased until the desired effect has occurred.
Depending on the severity of the disease, it may be necessary to take other medications in addition to carvedilol, for example ACE inhibitors, diuretics or cardiac glycosides.
What are the side effects of carvedilol?
During therapy with carvedilol, side effects in the form of dizziness, headache, cardiac insufficiency, low blood pressure and fatigue are seen in more than one in ten people treated.
In addition, the following side effects may occur in one in ten to one in one hundred people treated: Upper respiratory infections and inflammation, urinary tract infections, anemia, weight gain, high or low blood sugar levels in diabetics, high cholesterol levels, depression, and dry and irritated eyes.
Visual disturbances, slow heartbeat, water retention, dizziness when standing up, cold hands and feet, shortness of breath, asthmatic symptoms, nausea, diarrhea, vomiting, indigestion, pain in the limbs, kidney dysfunction, and erectile dysfunction are also possible.
What should be considered when taking Carvedilol?
Contraindications
Carvedilol should not be used in:
- unstable heart failure
- severe liver dysfunction
- metabolic acidosis (hyperacidity of the blood)
- certain excitation formation or conduction disorders in the heart (such as AV block grade II and III)
- severe hypotension (low blood pressure)
- bronchial asthma
Drug interactions
If other medications are taken during therapy with carvedilol, interactions between them may occur.
The beta-blocker carvedilol is transported in the body by certain proteins (p-glycoprotein) and broken down in the liver by certain enzyme systems (CYP2D6 and CYP2C9), which also metabolize other drugs. Therefore, taking additional drugs may result in excessively high or low drug levels of carvedilol. Examples:
When the heart drug digoxin is taken at the same time, its blood level increases. Regular blood level checks should therefore be carried out, particularly at the start of therapy.
In therapy with the immunosuppressant ciclosporin, which is used primarily after organ transplantation, concomitant treatment with carvedilol may result in higher ciclosporin blood levels. Therefore, blood level controls are also indicated in this case.
Drugs such as cimetidine (for acid-related stomach problems) and hydralazine (for example in heart failure) as well as alcohol can delay the breakdown of carvedilol in the liver. Its blood level may increase as a result.
Antiarrhythmic agents such as verapamil, diltiazem and amiodarone can cause serious conduction disturbances in the heart and cardiac arrhythmias if taken at the same time as carvedilol.
The simultaneous administration of substances that also have a blood pressure-lowering effect can cause an unexpectedly sharp drop in blood pressure. Such substances include the antihypertensive clonidine, other beta-blockers, barbiturates (sedatives and sleeping pills), tricyclic antidepressants, and alcohol.
Caution is advised for asthmatics – especially those who inhale long-acting agents for long-term treatment or short-acting bronchodilators for short-term treatment of dyspnea. In them, taking beta-blockers such as carvedilol can cause side effects such as acute dyspnea and asthmatic symptoms, as the effect of the asthma medication is cancelled out.
Age restriction
Carvedilol should not be used in children and adolescents under 18 years of age due to a lack of studies.
Pregnancy and lactation
Beta-blockers are generally among the most well-studied agents in pregnancy. This is particularly true of metoprolol. Its safety and efficacy data are better than those of carvedilol. Therefore, metoprolol should be preferred to carvedilol.
How to obtain medicines containing carvedilol
Preparations containing the active ingredient carvedilol can only be obtained from pharmacies in Germany, Austria and Switzerland after a doctor’s prescription.
How long has carvedilol been known?
Carvedilol is a third-generation beta blocker. It was approved as an active pharmaceutical ingredient in EU countries in the mid-1990s. In the meantime, numerous generics with the active ingredient carvedilol exist.
