How propranolol works
Propranolol belongs to the drug class of beta-receptor blockers (beta-blockers). As such, it acts in the autonomic nervous system, which controls blood pressure and heart function, among other things. In both cases, regulation takes place via certain nerve messengers (neurotransmitters), including primarily adrenaline.
This hormone is produced in the adrenal medulla and can bind to certain docking sites (beta receptors) on the heart, thus signaling an acceleration of the heartbeat. In addition, adrenaline can dilate the bronchi and stimulate and increase metabolism (glycogen and fat breakdown).
Propranolol competes with adrenaline for beta receptors and ultimately displaces the neurotransmitter. This means that adrenaline can no longer exert its heartbeat-increasing effect – with the result that the heartbeat slows down and blood pressure drops. Another important effect is that the heart’s oxygen consumption is reduced.
Unlike newer agents, propranolol is a non-selective beta blocker. This means that it inhibits both beta-1 receptors (found predominantly in the heart) and beta-2 receptors (found in the lungs, among other places). Because of this, the drug has now become less important in the treatment of heart disease.
Absorption, degradation and excretion
When is propranolol used?
Propranolol is a medication used for cardiovascular diseases. Indications for use in detail are:
- Hypertension
- Coronary heart disease
- certain forms of cardiac arrhythmia
- functional (not organically caused) heart complaints
- Muscle tremor of unknown cause (essential tremor)
- prevention of migraine
- hyperthyroidism (overactive thyroid gland)
In addition, the active ingredient can provide relief for simple anxiety (such as stress anxiety or anxiety before an exam). However, its use in this indication is off-label.
How propranolol is used
Propranolol is usually administered via the digestive tract, for example in tablet form or as a solution. How often and in what dosage the active ingredient must be taken is determined individually by the doctor.
In some cases, the active ingredient is administered intravenously, i.e. injected directly into a vein.
What are the side effects of propranolol?
Some side effects result from the effect on other receptors of the autonomic nervous system. For example, dizziness, headache, sweating, sleep disturbances, numbness and cold sensations in the limbs, and gastrointestinal complaints often occur. A drop in heart rate is also possible.
What should be considered when taking propranolol?
Contraindications
Propranolol should not be taken in the following cases:
- low blood pressure (hypotension)
- Heart muscle weakness associated with water retention in the tissues and shortness of breath (acute decompensated heart failure)
- Shock
- Disturbances in the formation or transmission of excitation in the heart (such as AV block grade II or III)
- concomitant use of calcium antagonists of the verapamil or diltiazem type (e.g., for high blood pressure or angina pectoris)
- concomitant use of MAO inhibitors = monoaminooxidase inhibitors (e.g. for depression and Parkinson’s disease)
Drug interactions
Some medicinal substances can enhance or even negatively influence the effect of propranolol on the heart and circulation and should therefore not be taken at the same time. These include:
- Cardiac glycosides (for the treatment of heart failure and cardiac arrhythmias)
- narcotics (anesthetics)
- Phenothiazines (used, for example, to treat psychosis)
- Blood pressure medications
Propranolol can increase the blood concentration of the migraine drug rizatriptan. Its dosage should therefore be no more than 5 milligrams.
Drugs that are broken down in the liver by the same enzyme system as propranolol may interact with the beta-blocker. A dose adjustment may then be necessary. This concerns, for example:
- Warfarin (anticoagulant)
- Theophylline (reserve medication for respiratory diseases)
Age restriction
Propranolol can be used in appropriate dosage from birth. If severe renal or hepatic impairment is present, the dosage must be adjusted.
Pregnancy and lactation
The beta-blocker may be used during pregnancy if necessary. Monitoring of the unborn or newborn child may subsequently be required. The use of propranolol during breastfeeding is also possible.
How to obtain medication with propranolol
Medicines containing propranolol require a prescription in Germany, Austria and Switzerland. This means they are only available by prescription.
How long has propranolol been known?
Propranolol was the first representative of the beta-blocker group of active ingredients. It was developed in the 1960s by James Whyte Black, who later won the Nobel Prize, and was launched on the market in 1964.
