Dual mechanism of action on cholesterol metabolism
To successfully dissolve cholesterol stones, it is necessary to sharply reduce the inflow of cholesterol into bile. Cholelitholytic agents achieve this through a powerful dual mechanism of action affecting two key points of lipid metabolism:
- At the intestinal level: the drugs purposefully disrupt the processes of cholesterol absorption from the lumen of the digestive tract. Thus, exogenous cholesterol does not enter the systemic circulation.
- At the liver level: there is direct inhibition of endogenous cholesterol synthesis. This is achieved through the pharmacological suppression of a specific enzyme — 3-hydroxy-3-methylglutaryl-CoA reductase (the abbreviation HMG-CoA reductase is more commonly used).
The result of this double blow is a pronounced decrease in cholesterol concentration in bile. Bile loses its lithogenic properties, the growth of old and the formation of new stones stops. In parallel, the drugs interact with the cholesterol already present in the calculi, forming liquid crystals or micellar solutions with it, which leads to the gradual dissolution of the stones.
Characteristics of main drugs
In modern clinical practice, drugs based on two bile acids are used for medical litholysis. A common rule for them is the time of administration: the medications are prescribed before bedtime. This is strictly justified by physiology, since it is during the night hours that the peak increase in cholesterol content in bile is observed.
- Chenodeoxycholic acid (trade name — Chenofalk). The main mechanism of dissolution is that the drug forms a micellar solution with cholesterol.
- Ursodeoxycholic acid (trade name — Ursofalk). Unlike the previous agent, it forms liquid crystals with cholesterol. It is taken once a day before bedtime. When comparing the two drugs, ursodeoxycholic acid demonstrates higher clinical efficacy. In addition, it has a better safety profile, since side effects during its administration are significantly less pronounced.
Principles of therapy and strict contraindications
The course of medical dissolution of gallstones requires discipline from the patient, as the therapy is very long. Depending on the clinical picture, treatment ranges from 3 months to 2 years of continuous drug administration.
At the same time, litholytic therapy has a number of strict contraindications. The drugs must not be prescribed in the following conditions:
- Pathologies of the gallbladder and ducts: the presence of stones whose diameter exceeds 2 cm, acute inflammatory processes in the biliary tract, as well as the syndrome of the «excluded» (completely non-functioning) gallbladder.
- Concomitant gastrointestinal diseases: any liver diseases, gastric ulcer and duodenal ulcer, chronic pancreatitis, and acute intestinal inflammations.
- Systemic body conditions: pregnancy and the presence of diabetes mellitus in the patient.
Side effects and management upon their occurrence
Despite general safety, undesirable reactions may develop during the administration of cholelitholytic agents (this is especially typical for chenodeoxycholic acid).
The main clinical manifestations include digestive system disorders: diarrhea, nausea, and epigastric pain. A temporary increase in liver transaminases may be recorded in blood laboratory parameters.
It is important to understand the dynamics of these conditions: as a rule, the listed undesirable reactions do not require specific treatment or discontinuation of the drug. They disappear completely on their own 2–3 weeks after the start of litholytic therapy.
Briefly: answers to topical questions
What are the indications for the use of ursodeoxycholic acid besides cholelithiasis?
In addition to cholelithiasis, ursodeoxycholic acid is used in non-alcoholic fatty liver disease to reduce lipid content in hepatocytes, reduce inflammation, and prevent the progression of fibrosis. It is also prescribed for primary sclerosing cholangitis as a hepatobiliary complication of inflammatory bowel diseases, and for cholestatic forms of acute viral hepatitis with a confirmed leading cholestasis syndrome and a protracted course of the icteric period.
What instrumental and laboratory methods are used to monitor the efficacy of litholytic therapy?
The provided guidelines lack data on specific instrumental and laboratory methods for monitoring the efficacy of litholytic therapy.
The «Two Barriers» rule: the drugs set up a block in the intestine (inhibit cholesterol absorption) and in the liver (inhibit its synthesis via HMG-CoA reductase). As a result, cholesterol simply has nowhere to come from to form stones.
Class and exam questions
Why must stone-dissolving drugs be taken specifically before bedtime?
This is due to the physiological rhythms of the body: it is during the night hours that the peak increase in cholesterol content in bile is observed.
What stones can be dissolved using these agents?
Litholytic therapy is aimed exclusively at dissolving cholesterol stones, while their diameter must not exceed 2 cm.
What to do if diarrhea and nausea appear in the first weeks of administration?
As a rule, nothing needs to be done. Side effects from the gastrointestinal tract and a temporary increase in transaminases usually disappear on their own after 2–3 weeks of therapy.
What else to study on this topic
- Biochemical foundations of the formation of micellar solutions and liquid crystals
- The role of the enzyme HMG-CoA reductase in lipid metabolism
- Criteria and diagnosis of the «excluded» gallbladder syndrome
- Comparative characteristics of the safety profile of chenodeoxycholic and ursodeoxycholic acids
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 «Cholelitholytic agents» and 5,304 more 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 section «Drugs Affecting Digestive System Functions»
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.