Lactulose Vs. Miralax: What's The Difference?

Lactulose and Miralax are both osmotic laxatives used to treat constipation and high ammonia levels. However, they have different mechanisms of action and varying degrees of effectiveness. Lactulose, a synthetic sugar, works by drawing water into the large bowel, softening stools, and increasing bowel movement frequency. On the other hand, Miralax, or Polyethylene Glycol, acts similarly to fibre laxatives, retaining water in the stool, making it softer, and stimulating more frequent bowel movements. While Lactulose can take up to 48 hours to work, Miralax usually works within 6 hours.

Dosage and administration

Lactulose and Miralax are both laxatives used to treat constipation. However, they are not the same and have different dosage instructions.

Lactulose

Lactulose is available as an oral solution or a powder that you mix with water and drink. It is typically taken once or twice a day, with doses depending on age and condition:

• For constipation in adults, the starting dose is 15ml, taken twice a day.
• For children aged 5-17 years, the dose is 5ml to 20ml, taken twice a day.
• For children aged 1-4 years, the dose is 2.5ml to 10ml, taken twice a day.
• For babies aged 1 month to 11 months, the dose is 2.5ml, taken twice a day.
• For adults with hepatic encephalopathy, the dose is 30ml to 50ml, taken three times a day.

Lactulose can be taken with or without food. It has a sweet taste, which some people may not like, so it can be mixed with half a glass of water or fruit juice. It is important to stay hydrated while taking lactulose, drinking 6 to 8 glasses of water or other liquids per day. The dosage can be adjusted depending on how well the medicine is working, and it can be taken long-term for severe constipation or hepatic encephalopathy.

Miralax

Miralax is an over-the-counter powder that is mixed with 4 to 8 ounces of water, juice, or other liquids. It is typically taken once daily, with a usual dose of 17 grams. It should not be used for more than two weeks unless directed by a doctor. It is important to follow the manufacturer's instructions and not to increase the dose or take it more frequently than prescribed. Miralax is not recommended for children under 16 years old.

Both medications can be taken with or without food. They should not be used for more than a week without consulting a doctor, and it is important to seek medical advice if constipation persists or worsens.

Effectiveness

Lactulose and Miralax are both osmotic laxatives, which work by drawing water into the large bowel (colon) from the surrounding tissue, thereby increasing fluid content and softening stools. However, they differ in their effectiveness.

Lactulose is a synthetic, non-digestible, sugar-like agent that helps to empty the bowel at a slow rate, taking 6 hours to 2 days to take effect. It can be taken orally or rectally. It is the first-choice treatment for brain conditions caused by high ammonia levels, as it pulls water into the bowel and also affects brain function by removing ammonia, a potent neurotoxin. However, it can cause severe dehydration and depletion of electrolytes, which can affect the heart. It also has a very sweet flavour that most people don't like.

On the other hand, Miralax (Polyethylene Glycol) is a polymer compound that consists of large molecules that help retain water in the stool, and it usually works within 6 hours. It is the most recommended laxative by pharmacists and doctors. It provides effective relief of constipation without causing cramping, bloating, gas, or feelings of urgency. It is also gluten and sugar-free. However, it is not for children 16 years or younger, and it can take up to 2-4 days to have a bowel movement. It is also not recommended for more than a week of use.

A meta-analysis of 10 separate studies found that polyethylene glycol (PEG), the active ingredient in Miralax, is more effective than lactulose in treating chronic constipation. PEG resulted in increased stool frequency, higher scores on the Bristol Stool Chart (which measures stool softness), and more effective relief of abdominal pain. Individuals using PEG also needed fewer additional products to relieve constipation than those taking lactulose.

Another randomized multicenter study comparing PEG and lactulose for functional constipation found that PEG was more effective and had fewer side effects, such as abdominal pain and bloating.

Side effects

Lactulose and Miralax are both laxatives used to treat constipation. However, they are not the same medication. Lactulose is a prescription medication, while Miralax is available over the counter.

Both medications may cause side effects, some of which can be serious.

Lactulose Side Effects

According to the NHS, diarrhoea is a very common side effect of lactulose, occurring in more than 1 in 10 people, especially at high doses. Other common side effects, which occur in more than 1 in 100 people, include wind (farting and burping) and feeling or being sick (nausea and vomiting). These side effects are usually mild and go away after a few days.

Serious side effects are rare, occurring in less than 1 in 100 people. However, if you experience severe diarrhoea or vomiting for more than a couple of days, along with muscle cramps or weakness, or an irregular heartbeat, this could be a sign of a dangerous electrolyte imbalance.

In rare cases, a serious allergic reaction (anaphylaxis) may occur. Symptoms of a serious allergic reaction include sudden swelling of the lips, mouth, throat or tongue, breathing difficulties, a tight throat, skin discolouration, confusion, dizziness, or fainting. If you experience any of these symptoms, seek immediate medical attention.

Miralax Side Effects

Miralax may also cause mild side effects, including bloating, gas, and an upset stomach.

Serious side effects are rare but may include severe or bloody diarrhoea, blood in stools, and severe and worsening stomach pain.

An allergic reaction to Miralax can be dangerous and life-threatening. Symptoms include hives, difficulty breathing, and swelling of the face, lips, tongue, or throat. If you experience any of these symptoms, seek emergency medical help.

Safety

Lactulose and Miralax are both laxatives used to treat constipation. However, they have different active ingredients and mechanisms of action, and therefore may have different side effects and safety profiles. Here is a detailed overview of the safety considerations for each medication:

Lactulose Safety:

Lactulose is a synthetic sugar that breaks down in the large intestine, drawing water into the intestine to soften stool and relieve constipation. It is available as a prescription oral solution (brand name: Generlac) and as a rectal solution administered as an enema by a healthcare provider.

Side Effects:

Common side effects of lactulose may include cramps anywhere in the body. More severe side effects may include allergic reactions, severe diarrhea, and stomach discomfort or pain. It may also cause an increase in blood sugar levels, so individuals with diabetes should use it with caution. Lactulose may also interact with other medications, such as antacids and antibiotics, reducing its effectiveness.

Precautions:

Lactulose is not suitable for those with problems digesting galactose, as it contains galactose and lactose (milk sugars). It should be used with caution during pregnancy and breastfeeding, as there are limited studies on its effects on the fetus and nursing infant. The safety and effectiveness of lactulose for constipation in children under 18 have not been established.

Miralax (Polyethylene Glycol) Safety:

Miralax is an over-the-counter medication that provides effective relief from constipation without causing cramping, bloating, gas, or an urgent need to use the bathroom. It is the most recommended laxative by pharmacists and doctors.

Side Effects:

Common side effects of Miralax may include diarrhea, bloating, and nausea. Although rare, there have been reports of neuropsychiatric problems in children who have taken Miralax, including mood and behavioral changes, depression, anger, anxiety, and mood swings. However, these effects may be due to underlying conditions rather than the medication itself, and further studies are ongoing.

Precautions:

Miralax is not recommended for children under 17 years of age, and the label advises against using it for more than seven days. It is not suitable for those on a galactose-restricted diet. While it is not approved by the FDA for use in children, this does not necessarily indicate that it is unsafe.

In summary, both Lactulose and Miralax have their own unique safety profiles, and it is important to consult a healthcare professional before taking either medication to ensure it is suitable for your individual needs and circumstances.

Drug interactions

Lactulose and Miralax are both laxatives used to treat constipation and high ammonia levels in the body. However, they are not the same drugs and have different chemical compositions. Lactulose is a prescription drug, while Miralax is available over the counter.

Lactulose Drug Interactions

Lactulose is known to interact with a total of 246 drugs, with 233 moderate interactions and 13 minor interactions. It is important to note that these numbers reflect the currently known interactions, and there may be other interactions that have not yet been identified.

Some of the most frequently checked interactions with lactulose include:

• Aspirin Low Strength (aspirin)
• Benadryl (diphenhydramine)
• Cymbalta (duloxetine)
• Fish Oil (omega-3 polyunsaturated fatty acids)
• Lantus (insulin glargine)
• Lexapro (escitalopram)
• Linzess (linaclotide)
• Lipitor (atorvastatin)
• Metoprolol Succinate ER (metoprolol)
• Miralax (polyethylene glycol 3350)
• Nexium (esomeprazole)
• Norco (acetaminophen / hydrocodone)
• Paracetamol (acetaminophen)
• Plavix (clopidogrel)
• Prilosec (omeprazole)
• Protonix (pantoprazole)
• Seroquel (quetiapine)
• Symbicort (budesonide / formoterol)
• Synthroid (levothyroxine)
• Tylenol (acetaminophen)
• Vitamin B12 (cyanocobalamin)
• Vitamin C (ascorbic acid)
• Vitamin D3 (cholecalciferol)
• Zofran (ondansetron)

In addition to these drug interactions, lactulose also has four known disease interactions:

• Inflammatory bowel disease
• Intestinal obstruction disorders
• Portal systemic encephalopathy
• Diabetes (due to the presence of lactose and galactose in the preparation)

Miralax Drug Interactions

Miralax (polyethylene glycol 3350) is known to interact with 219 drugs, with 218 moderate interactions and 1 minor interaction. Again, these numbers reflect currently known interactions, and there may be others that have not yet been identified.

Some of the most frequently checked interactions with Miralax include:

• Benadryl (diphenhydramine)
• Flonase (fluticasone nasal)
• Tylenol (acetaminophen)
• Vitamin B12 (cyanocobalamin)
• Vitamin C (ascorbic acid)
• Vitamin D3 (cholecalciferol)
• Zofran (ondansetron)

Miralax also has three known disease interactions:

• Inflammatory bowel disease
• Intestinal obstruction disorders
• GI obstruction/perforation

Both lactulose and Miralax have a moderate to high number of drug interactions, with some overlap in the types of interactions observed. It is important for patients to consult with their healthcare providers before taking either of these medications, especially if they are currently taking other prescription or over-the-counter drugs.

Frequently asked questions