Avapena: Formula, Presentation, Indications, Mechanism of Action, Dosage, Side Effects and Interactions

It is a first generation antihistamine medication certified in some Eastern European countries.

The active ingredient in avapena is chloropyramine hydrochloride.

Chemical formula

  • ‎C16H20ClN3.


  • Box containing 20 25 mg tablets.


  • When there are conditions such as allergic rhinitis , allergic conjunctivitis , hay fever, pruritus , acute skin allergies, urticaria , Quincke’s edema, acute eczema and other conditions.
  • In case of allergies to food or drugs.
  • In case of bites or insect bites.
  • As a preventive measure for the reactions induced by the use of contrast media, as a pre-operative treatment in patients with allergy problems.
  • In the processes of bronchial asthma .

Mechanism of action

Avapena is distinguished as an antagonist that competes with the reversible histamine H1 receptor, known as the inverse agonist H1.

This means that Avapena exerts its pharmacological action competing with histamine for subtype H1 which is the receptor for histamine.

By blocking the effects produced by histamine, the drug prevents the occurrence of vasodilation, an increase in vascular permeability and the appearance of tissue edema, which is associated with the release of histamine in the tissue. Avapena also has anticholinergic properties .

The drugs that are responsible for blocking the receptors for histamine are classified as pharmacological antagonists.

They seem to act by inhibiting the receptors in the cell that performs the action, excluding the agonist molecules, without actually initiating any response by themselves. In this case of the histamine antagonists, the action that is carried out is competitive and reversible.

These blockers H1 are absorbed very well by the gastrointestinal tract, so after oral administration, the effects can appear in 15 to 30 minutes, maximum in 1 to 2 hours and the effect lasts from 3 to 6 hours.

Plasma concentrations have a direct relationship with the antagonistic effect of histamine and the sedative effect.

This drug is distributed throughout the body including in the central nervous system.

It is excreted without change through urine and for the most part occurs in the urine as a degradation product, which are excreted in 24 hours.

The place where the metabolic transformation takes place mainly is in the liver.


The dose should be individualized for each case in relation to the therapeutic response of each of the patients.

However, as a general rule, the following doses are recommended:

In adults:

An initial dose of two to three tablets a day.

In children:

From 5 to 10 years, administer one to two tablets a day. Over 10 years, two to three pills a day. In children under 5 years of age Avapena should not be administered.

Side effects

The anticholinergic properties of chloropyramine are intimately related to the side effects caused by treatment such as:

Weakness, dizziness , fatigue, dizziness, drowsiness, dry mouth, nausea, constipation, diarrhea, stomatalgia, lack of coordination and rarely, visual disturbances and increased intraocular pressure.

Warnings and contraindications

Special caution should be exercised for possible secondary reactions such as drowsiness in patients, mainly when driving vehicles or operating precision machinery.

This drug should not be administered in case of hypersensitivity to the active substance ( chloropyramine hydrochloride ), high blood pressure , prostatic hyperplasia , respiratory failure.

Peptic ulcers in the gastrointestinal tract, cardiac arrhythmia , angle-closure glaucoma, simultaneous reception of monoamine oxidase inhibitors and other drugs that depress the central nervous system.

The safety in the use of this drug in pregnancy and in the period of lactation has not yet been determined, therefore for administration the relationship of the beneficial effects expected and the risks must be carefully evaluated.

It should not be administered to children under 5 years of age.

During treatment, potentially risky activities that require more attention should be avoided.


This drug interacts with alcohol, tricyclic antidepressants, barbiturates or any central nervous system depressant drug.

Improves the action of drugs for general anesthesia, hypnotics, sedatives, opioid analgesics and local anesthetics.

High doses can be altered laboratory tests showing signs of agranulocytic thrombocytopenia, hemolytic anemia and aplastic anemia.


In case of overdose, in children it causes anxiety, hallucinations, athetosis, ataxia , seizures, excitement, mydriasis , immobility of the pupils, facial flushing, hyperthermia, vascular collapse, coma, etc.

And in adults it causes depression, lethargy, hyperthermia and hyperemia of the skin, psychomotor agitation, seizures, coma, etc.

There is no specific treatment for an overdose of blockers, the treatment is usually a gastric lavage, mechanical support with ventilation is essential in the case of respiratory failure.

If seizures occur, it is best to fight them with a depressant such as thiopentalo diazepam, whose effects are rapid, transient and controllable.