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 Alpena is chloropyramine hydrochloride.

Chemical formula

  • ‎C16H20ClN3.


  • Box containing 20 25 mg tablets.


  • Allergic rhinitis, 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 contrast media, as a pre-operative treatment in patients with allergy problems.
  • In the processes of bronchial asthma .

Mechanism of action

Alpena 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 by competing with histamine for subtype H1, 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. Alpena also has anticholinergic properties.

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

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


These blockers H1 are absorbed very well by the gastrointestinal tract. 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 directly relate to 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 is passed within 24 hours.

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


The dose should be individualized for each case about 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 ten years, two to three pills a day. In children under five 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

Particular 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 pressureprostatic hyperplasia, or 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 of using this drug during pregnancy and in the period of lactation has not yet been determined; therefore, for administration, the relationship between the beneficial effects expected and the risks must be carefully evaluated.

It should not be administered to children under five 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 through laboratory tests showing agranulocytic thrombocytopenia, hemolytic anemia, and aplastic anemia.


In case of an 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, and 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 thiopental diazepam, whose effects are rapid, transient, and controllable.