Mechanism of action and secretory physiology
Normally, hydrogen ion (H⁺) secretion is performed by oxyntic (parietal) cells of the stomach. This process is strictly regulated by the central nervous system and humoral factors via three main stimulation pathways:
- Neuronal: acetylcholine stimulates M₃ muscarinic receptors (the signal is transmitted via the vagus nerve).
- Paracrine: histamine locally affects H₂ histamine receptors. Histamine release itself is provided by enterochromaffin-like cells when the cholinergic system stimulates their M₁ receptors.
- Humoral: gastrin activates CCK₂ receptors.
The intracellular signaling cascade (e.g., upon H₂ receptor activation) involves receptor coupling with a Gs protein, activation of adenylyl cyclase, cAMP accumulation, and activation of cAMP-dependent protein kinases. The ultimate target is the H⁺, K⁺-ATPase enzyme ("proton pump"), which transports hydrogen ions from the cell into the gastric lumen in exchange for potassium ions.
Administration of Acidum hydrochloricum dilutum does not affect these receptor mechanisms. The drug works on the principle of replacement therapy — it physically replenishes the deficiency of endogenous hydrochloric acid in the gastric lumen.
Pharmacological effects
The drug recreates the necessary acidic environment in the stomach (gaster). This is critical for the normal digestive process: the acidic environment ensures protein denaturation and digestion, and is also necessary for the activity of proteolytic enzymes (pepsin).
From a pharmacokinetic perspective, hydrochloric acid acts as a potent chemical barrier. It destroys acid-labile substances (e.g., benzylpenicillin) and is one of the factors reducing the bioavailability of many orally administered drugs before they reach the portal vein and liver. The stomach is only the first stage of transit. The main site of drug absorption into the venous bed is the small intestine (intestinum tenue), where chyme enters after acid treatment.
Indications for use
The main indication is insufficiency of digestive gland function accompanied by a decrease or complete absence of endogenous hydrochloric acid production.
The drug is used strictly as part of replacement therapy. It is important to remember that such treatment does not eliminate the cause of the disease (etiology) and does not affect the mechanisms of its development (pathogenesis). The goal of therapy is to alleviate the manifestations of a vital substance deficiency. The nature of use in such cases is usually long-term (course-based or lifelong).
Interaction with other substances and the GI environment
- Antacids: enter into a direct chemical reaction with hydrochloric acid (extracellular mechanism), neutralizing it. This leads to impaired protein denaturation and digestion.
- Effect of food: food slows down the evacuation of gastric contents, which delays the passage of drugs into the intestine and reduces their absorption rate. Lipophilic substances are an exception: fatty foods stimulate bile secretion, improving their emulsification and absorption.
- Drug protection from acid: to protect acid-labile drugs from destruction by hydrochloric acid, enteral dosage forms (tablets or capsules with an acid-resistant coating) are used. They pass through the stomach unchanged and disintegrate only in the small intestine. An alternative is sublingual or buccal administration, in which lipophilic non-polar substances are absorbed via passive diffusion in the oral cavity, bypassing the aggressive gastric environment and the first-pass hepatic effect.
Administration features and risks
The drug is available in 15, 30, and 100 ml bottles. It is prescribed orally (per os). Recommended dosage: 10–15 drops, which must be diluted in 1/2 glass of water. Taken 3–4 times a day.
Clinical note on mucosal protection: Excess hydrochloric acid in the stomach is extremely dangerous when mucosal defense factors are reduced. For example, when taking ulcerogenic drugs (NSAIDs), there is unreactive inhibition of the COX-1 enzyme. This reduces the synthesis of prostaglandins (E2 and I2) responsible for producing protective mucus and bicarbonates. Under such conditions, acid damages the gastric wall (NSAID-gastropathy develops). Washing down drugs with milk for acid protection is an ineffective measure: milk provides only a temporary buffering effect, and calcium ions can secondary stimulate hydrochloric acid secretion. Proton pump inhibitors or prostaglandin analogues are required for gastroprotection.
Briefly: answers to topical questions
Which digestive enzymes are activated by hydrochloric acid in the stomach?
Hydrochloric acid in the stomach activates inactive proenzymes, pepsinogens, converting them into active proteolytic enzymes, pepsins.
The activation process proceeds in two stages:
- Slow stage — carried out directly by means of hydrochloric acid.
- Fast stage — proceeds autocatalytically under the action of already formed pepsin.
In addition, hydrochloric acid creates an optimal acidic environment for enzyme activity and causes denaturation and swelling of food proteins, which prepares them for hydrolysis and facilitates enzyme access to peptide bonds.
The parietal cell awaits three guests: Acetylcholine (M3), Histamine (H2), and Gastrin (CCK2) to turn on the proton pump (H+, K+-ATPase).
Class and exam questions
What type of pharmacotherapy does the prescription of diluted hydrochloric acid belong to?
This is replacement therapy. It does not eliminate the etiology of the disease, but replenishes endogenous acid deficiency in hypofunction of the digestive glands.
How to protect acid-labile drugs (e.g., benzylpenicillin) from destruction in the stomach?
It is necessary to use enteric dosage forms with an acid-resistant coating, or choose routes of administration that bypass the gastrointestinal tract (e.g., sublingual).
Why does hydrochloric acid begin to damage the stomach when taking NSAIDs?
NSAIDs block the COX-1 enzyme, which causes the synthesis of protective prostaglandins (E2, I2) to drop. Without them, the production of mucus and bicarbonates ceases, and acid aggressively affects the stomach wall.
Is it possible to wash down ulcerogenic drugs with milk to neutralize the acid?
No. Milk provides only a short-term buffering effect, and the calcium ions it contains are capable of secondary stimulating hydrochloric acid secretion.
What else to study on this topic
- Intracellular mechanism of H+, K+-ATPase (proton pump) action
- Differences between replacement, symptomatic, and pathogenetic therapy
- Gastrointestinal absorption mechanisms: passive diffusion and the role of P-glycoprotein (efflux)
- The effect of antacids on the pharmacokinetics of other drugs
- First-pass hepatic effect and presystemic metabolism
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 "Diluted hydrochloric acid" and another 5,304 pages of the subject
- 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.