Atropine: Features And Side Effects

Atropine is a drug that acts as an antagonist to the muscarinic acetylcholine receptors and has many pharmacological effects. Read all about this in this article!
Atropine: Functions and side effects

Atropine is a type of medicine. Doctors use it for many different things. It has mydriatic, antispasmodic, anti-diarrhea, anti-catarrhal and anesthetic properties.

This active substance comes from the belladonna plant and other plants in the sweet pea family. Since ancient times, Hindus have used preparations made from the belladonna plant. Later, in the Roman Empire and the Middle Ages, they used them for toxic purposes.

Throughout this article, we will explain the following about atropine in more detail:

  • How it works
  • Its pharmacokinetics
  • Its pharmacological effects
  • Side effects

Before we begin, however, you need to know what acetylcholine receptors are to better understand how they work.

Acetylcholine receptors

atropine - features and side effects

Acetylcholine receptors are a group of receptors that also include two other types of receptors. These are muscarinic and nicotinic acid. Basically, they are located in the synaptic cleft. They are mostly at the postganglionic level. However, there are some at the presynaptic level.

All neurotransmitter systems have receptors at the presynaptic level. This is because they  modulate the amount of acetylcholine to be released.

Acetylcholine is a substance that is synthesized in the cytoplasm of motor neurons and activates acetylcholine receptors directly. However, very few presynaptic receptors trigger the secretion of this substance.

Atropine: How does it work?

Basically, atropine is an antagonist of the muscarinic acetylcholine receptors. As we have seen, acetylcholine is a substance that activates these receptors directly.

This means that it  inhibits the parasympathetic nervous system. The main explanation for this lies in the fact that acetylcholine receptors are in parasympathetic effectors. So when someone takes atropine, it affects the heart, eyes and digestive tract, among other organs.


fetus in the womb

Overall, this medicine can be taken orally, intravenously and in many other ways. If administered orally, it is easily absorbed in the digestive tract. Then it travels through the blood.

It is a very soluble substance. This means that it is able to cross the blood-brain barrier and the placenta. Thus, pregnant women should be especially careful  if they are being treated with atropine.

It has a half-life of about two to three hours. Furthermore, the liver metabolizes between 50 and 75%. The body then excretes both metabolites and the fraction of non-metabolised substances in the urine.

Pharmacological effects

Atropine  blocks the activity of muscarinic acetylcholine receptors. Basically, this means that it does not allow acetylcholine to interact with these receptors.

It does this gradually in a variety of structures such as saliva, submucosa and sweat glands, vascular smooth muscle, cardiovascular system, digestive system and urinary tract, gastric glands and autonomic ganglions.

Since it is an anti-cholinergic agent in all these body parts, some of the things it triggers are:

  • Tachycardia. This is why it is used to increase the heart rate in emergencies.
  • At the digestive level  , it minimizes peristaltic and gastrointestinal spasms, cramps and secretions.
  • This  makes urination difficult. This is problematic in patients with benign prostatic hyperplasia.
  • Mydriasis. It blocks the ciliary muscle, causing spasms. However, the drug does not inhibit the muscarinic receptors in the eyes if administered orally.

Side effects of atropine

The side effects of this drug are related to the dose. They are common reactions, especially in children. Furthermore, atropine can build up and produce systemic effects after multiple doses by inhalation in the elderly.

In adults, the most common side effects are:

  • Dry mouth
  • Red and hot skin due to lack of sweat
  • Fever
  • Constipation

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