Chemical Composition and Mechanism of Action of Lactulose


What is Lactulose?

Lactulose is a synthetic disaccharide that is commonly used as a treatment for constipation and hepatic encephalopathy. It belongs to a class of medications known as laxatives. Lactulose was developed in the 1960s as a treatment for constipation in hospitalized patients. Since then, it has become one of the standard medications prescribed to help relieve constipation and manage related issues.

Chemical Composition and Mechanism of Action

Lactulose is composed of galactose and fructose sugars that are bonded together. However, unlike most sugars, it is not broken down or absorbed by the small intestine. Instead, it passes undigested into the colon where it is fermented by the natural bacteria that reside there. During the fermentation process, lactulose promotes the growth of ‘good’ bacteria in the colon while producing organic acids like lactic acid. These organic acids help lower the colonic pH which draws fluid into the intestinal contents from surrounding tissue, resulting in softer stools that are easier to pass. The increased bacterial growth also produces gases that help stimulate bowel movements. In addition, lactulose competes with ammonia absorption in the colon, facilitating the excretion of ammonia via stools. This property makes it effective for treating hepatic encephalopathy.

Uses and Effectiveness for Constipation

Lactulose is commonly prescribed to treat occasional constipation in otherwise healthy individuals. It works gently over 1-2 days to soften stools and stimulate bowel movements without severe cramps. Studies have shown lactulose to be as effective as other commonly used osmotic laxatives for relief of constipation. It is also one of the standard first-line treatments recommended for constipation in clinical guidelines. For long-term treatment of chronic constipation, lactulose provides consistent relief of symptoms when taken as prescribed on a regular basis. It is particularly useful for the elderly and bedridden patients who are more prone to constipation due to reduced mobility and dietary changes.

Uses and Effectiveness for Hepatic Encephalopathy

Lactulose is the most preferred treatment worldwide for hepatic encephalopathy, a neurologic syndrome caused by severe liver dysfunction. It acts by reducing the levels of toxic ammonia in the body, which is normally processed by the liver but builds up in conditions of severe liver damage. By promoting bacterial fermentation in the colon, lactulose reduces the absorption of ammonia from the gastrointestinal tract and facilitates its excretion in stools. Large clinical studies have proven the effectiveness of lactulose in significantly improving neurological symptoms of hepatic encephalopathy such as confusion, disorientation and cognitive decline. It helps prevent recurrent episodes of encephalopathy and reduced mortality in patients with cirrhosis when taken on a long-term basis. Lactulose remains the gold standard treatment for all grades of hepatic encephalopathy, at least as initial therapy.

Dosage, Side Effects and Precautions

The dose of lactulose varies depending on its indication and severity of the condition being treated. For constipation, the usual starting dose is 15-30 ml taken once or twice daily. Higher doses of 30-60 ml taken 2-3 times daily are used for hepatic encephalopathy. Side effects may include abdominal cramps, excess gas, nausea and diarrhea due to its osmotic effect in the colon. These are usually mild and self-limiting. Lactulose therapy may lower serum potassium levels in some people and exacerbate existing electrolyte imbalances. It should be used with caution in patients having severe renal disease or lactose intolerance. As lactulose is not absorbed, it can usually be continued during pregnancy. However, it is always advisable to consult a healthcare provider before starting any medication during pregnancy.

Lactulose syrup has become a trusted first-line treatment for different gastrointestinal issues related to constipation as well as hepatic encephalopathy. Over 60 years of clinical use has established its efficacy and safety profile. As an osmotic laxative with colonic fermentation properties, it works gently to stimulate bowel movements and improve symptoms. Lactulose provides effective relief from constipation and helps manage complications of liver disease like hepatic encephalopathy. With regular use as prescribed by healthcare providers, it can help control related symptoms long-term with minimal side effects.

1. Source: Coherent Market Insights, Public sources, Desk research
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