Active Ingredients

Astemizole – Effect, Application & Risks


Astemizol is a so-called antihistamine that is used to treat allergies symptomatically. However, this drug is no longer available on the German market.

What is astemizole?

Astemizole is an H1-receptor antagonist and second-generation antihistamine. By blocking the histamine receptors , the formation of the messenger substance histamine is canceled or at least weakened by astemizol.

Unlike first-generation preparations, astemizol cannot cross the blood-brain barrier and thus cannot enter the central nervous system. Astemizol, like similar preparations, came onto the market from 1984. In Germany and Austria, this preparation was sold under the brand name Hisamanal.

This preparation has now been withdrawn from the market in most countries. The reason: In rare cases, there can be strong interactions with some enzyme inhibitors . However, research into the drug continues. A possible area of ​​application could be tumor therapy in the future .

Pharmacological action

Astemizole has been used to treat allergic conjunctivitis , allergic rhinitis , hay fever , and hives , and has been administered orally.The active ingredient binds the H1 receptors in the blood vessels , in the muscles of the bronchi , in the gastrointestinal tract and in the uterus . Astemizole is rapidly absorbed by the body from the gastrointestinal tract, so it has a half-life of only 24 hours.

Because the drug binds to a receptor, astemizole is called a competent antagonist. The active ingredient therefore occupies the receptors and forms a complex with them. By displacing the messenger substance histamine from the H1 receptors, astemizol has an antiallergic effect. This prevents symptoms such as itching , swelling and reddening of the skin.

In addition, the preparation has an anticholinergic effect because it also docks to the muscarinic receptors. This is a membrane-resistant receptor in which acetylcholine, one of the most important neurotransmitters in the human organism, is produced. This plays an important role in the transmission of stimuli between nerves and muscles . This messenger substance is linked to numerous cognitive processes, which is why it is also an important factor in connection with diseases such as Alzheimer’s disease . Because this disease is also expressed by a lack of that messenger substance.

Medical Application & Use

The preparation Astemizol was used to weaken or completely neutralize the effect of the messenger substance histamine. The most important application is the treatment of allergic symptoms. In addition to itching and reddening of the skin, this also includes inflammation of the body and the conjunctiva of the eye.

The first-generation H1 antihistamines were replaced by preparations such as Astemizole, because the former could very easily cross the blood-brain barrier, allowing the active ingredients to penetrate quickly into the central nervous system . This significantly reduced the possible side effects.

Second-generation preparations such as Astemizol have now been taken off the market in Germany and many other countries and have been replaced by newer preparations. These cause fewer side effects and also offer other therapeutic advantages.

Due to the relatively long half-life of 24 hours, astemizole offered patients who tolerated the preparation the advantage that a single daily dose was sufficient. The preparation, which was mainly absorbed by the body in the gastrointestinal tract, was excreted in the faeces.

Risks & side effects

In addition to minor side effects such as dry mouth , fatigue and disturbances in the gastrointestinal tract, astemizol had mainly cardiological side effects. In addition to cardiac arrhythmias , the preparation could also cause cardiac arrest or ventricular fibrillation .Although these side effects were rare, they were very severe. As a result, the use of astemizole has been completely phased out in many countries and greatly reduced in others.

The side effects affecting the heart have proven to be particularly severe in patients who have suffered from liver damage or QT prolongation. This is because the potassium channels are blocked within the heart muscle . In extreme cases, this blockage can lead to a torsades de pointes tachycardia, which becomes noticeable through a heart rate of 150 beats per minute. In extreme cases, this can turn into ventricular fibrillation and thus represent a life-threatening situation for the patient.


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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.