Mechanism of action and physiological principles
The action of the drug Acidin-pepsin (Acidin-pepsini) is based on the replacement effect — it artificially compensates for the deficiency of the stomach's own secretion (gaster).
Under physiological norms, parietal cells secrete hydrochloric acid (HCl). The mechanism of proton ($H^+$) transport from the cell cytoplasm across the membrane occurs in exchange for potassium ions ($K^+$). This creates a colossal gradient: inside the cell, the pH is 7.8, while in the gastric lumen, it is 0.8.
This sharply acidic environment is absolutely necessary for the functioning of proteolytic enzymes. The main one is pepsin, which carries out proteolysis (breakdown of protein structures). By taking the drug orally (per os), we deliver the ready-made enzyme and substrate to the stomach to create an acidic environment, triggering the digestive process even in the event of atrophy of the body's own glands.
Pharmacokinetics
The drug exerts its effect prior to absorption. Unlike most medicinal substances, for which the small intestine is the main site of absorption into the venous bed (portal vein for the first-pass effect) or the lymphatic duct, Acidin-pepsin works exclusively in the gastric lumen. It interacts with the food bolus and is subsequently destroyed or inactivated in the alkaline environment of the intestine.
Indications and place in combination therapy
The main indication is hypoacid conditions (reduced acidity) and insufficient enzyme production.
Gastric acidity directly affects the efficacy of other drugs. For example, the herbal preparation Nigedaza (a lipolytic from black cumin seeds) is less active at low acidity. In such cases, it is recommended to wash it down with gastric juice. Acidin-pepsin can serve as a pharmacological alternative, creating the required pH background for lipolytics to work.
Also, the drug is conceptually close to agents containing bile (where the gastric mucosa extract contains pepsin and cathepsin), which are prescribed for the comprehensive replenishment of gastric and pancreatic secretion deficiencies.
Mucosal defense factors and adverse effects
The introduction of exogenous acid and pepsin is the delivery of aggressive factors into the stomach. Normally, the epithelium is protected by a powerful gastroprotection system, the regulation of which depends on prostaglandins ($E_2$ and $I_2$):
- Mucus: Hydrophilic glycoproteins form a physical gel that protects the wall from acid and pepsin.
- Blood supply: Ensures the "washout" of hydrogen ions (back diffusion).
- Bicarbonates: Neutralize acid on the cell surface.
If the drug is taken on an empty stomach or the dose is exceeded, the aggressiveness of pepsin and HCl may exceed the protective potential of the mucosa.
Clinical parallel: Excess acid and pepsin lead to mucosal damage. This is clearly manifested during long-term therapy with systemic glucocorticoids, which stimulate the secretion of HCl and pepsin, causing an ulcerogenic effect ("steroid" ulcers).
In hyperacid conditions and peptic ulcer disease, Acidin-pepsin is strictly contraindicated. In such situations, drugs with the opposite effect are used: antacids (magnesium oxide, algeldrate), $H_2$-histamine receptor blockers (reduce basal secretion of acid and pepsin), or gastroprotectors (sucralfate, which locally neutralizes HCl and reduces pepsin activity).
Prescribing and administration rules
The drug is available in 0.25 g tablets.
- Dosage: Orally 0.2–0.5 g per single dose.
- Frequency: 3–4 times a day.
- Relation to food: Strictly during or immediately after meals. This is critically important so that the enzyme breaks down food proteins rather than attacking the gastric mucosa.
ACIDin (acidum — acid) + PEPSIN (enzyme) = artificial gastric juice for protein digestion.
Class and exam questions
Why should Acidin-pepsin be taken strictly during or after meals?
So that exogenous hydrochloric acid and the proteolytic enzyme (pepsin) interact with the food bolus. Taking it on an empty stomach will lead to an aggressive effect on the gastric mucosa.
How does the gastric mucosa normally protect itself against the aggression of pepsin and acid?
The basis of gastroprotection is mucus (hydrophilic glycoproteins), bicarbonate secretion, and adequate blood supply. A key role in stimulating this defense is played by prostaglandins E2 and I2.
In which iatrogenic pathologies is an excess of pepsin and HCl observed?
During long-term therapy with systemic glucocorticoids. They stimulate the secretion of hydrochloric acid and pepsin, which leads to an ulcerogenic effect (formation of ulcers).
What else to study on this topic
- Physiology of hydrochloric acid secretion: the work of the proton pump and ion exchange.
- Aggression and defense factors of the gastric mucosa (the role of prostaglandins).
- Ulcerogenic effect of medicinal products (using glucocorticoids as an example).
- Pharmacology of antacids (absorbable and non-absorbable drugs).
- Mechanism of action of H2-histamine receptor blockers and sucralfate.
Master the entire topic in the «Pharmacology» course
This is a summary. The course covers everything tested in classes and exams.
- Complete study guide on "Acidin-pepsin" and 5,304 more subject pages
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 116 video lessons on the subject
Other topics in the «Drugs and Prescriptions» section
Free video lessons: pharmacologyShort lessons with study notes — no registration required.
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.