You know how our parents always told us to eat more vegetables and fruits when we were younger? Like it helps with digestion and all that stuff? I really hope most of us carried that through to adulthood because let’s just say constipation ain’t fun guys. But of course there may be very different reasons as to why someone has constipation. It’s not always due to one’s diet. However, more often than not, it is the lactulose syrup that comes to the rescue and that’s not all that there is to it. Allow me to break it down for you.  

Lactulose, a non-absorbable synthetic disaccharide, is available orally in the form of a sweet syrup and rectally as a suppository. Being an osmotic laxative, it greatly benefits those with constipation. Just to point it out, our small intestine’s mucosa, which has various enzymes, does not in fact have the enzymes to split lactulose. So, the lactulose reaches the large intestines unchanged. 

Anyway, do you know what leads to constipation? It’s when all the food that we’ve eaten, metabolized and digested culminates as stools and remains in the colon for way too long than what’s considered normal. Thus, causing the colon to absorb too much water from the stools, making them hard and dry (www.nhsinform.scot, 2023). That’s when we find it hard to go to the toilet as usual. Lactulose helps in this sense because of its osmotic ability whereby it pulls water from the less concentrated side outside of the colon into the colon itself (which is more concentrated due to the breakdown of lactulose into organic acids) and aids in softening the stool, allowing them to move out through peristalsis. And just like that, you’re able to go to the toilet without a worry. In adults, the oral dose usually ranges from 15 ml up to to 60 ml with varied frequencies depending on the severity of the constipation (UptoDate, 2023). 

I did mention earlier that lactulose suppositories are available, didn’t I? Well those aren’t indicated for constipation but they can be used in treatment of Hepatic Encephalopathy. Hepatic encephalopathy (HE), which presents itself as an array of neuropsychiatric abnormalities brought on by severe liver disease (can be acute or chronic) such as those with cirrhosis or transjugular intrahepatic portosystemic shunt (TIPS). To understand where lactulose fits into this equation, we will first need to understand how HE occurs.

In an individual with normal liver functions, the bacteria in the gastrointestinal tract (GIT) will produce ammonia which will be metabolised and removed via the liver. However, when advanced liver dysfunction is present, ammonia clearance is reduced, leading to hyperammonemia. This can be due to a decrease in functioning hepatocytes, portosystemic shunting or both. The elevated serum ammonia levels can cross the blood brain barrier leading to neurotoxic effects (Tranah, Paolino and Shawcross, 2015). As such, one of the major concerns here is to reduce the ammonia level in the body. Fortunately, HE is a reversible condition and lactulose comes to the rescue here. 

Lactulose when consumed, is broken down into lactic acid and several other organic acids by the gut bacteria. The presence of these acids causes acidification of the gut lumen and thus, conversion of ammonia (NH3) to ammonium (NH4+) which is in its ionised form. Therefore, preventing the ionised molecule, NH4+ from crossing the gut membrane and travelling into the bloodstream. As such, NH4+ will be excreted out through the faeces and reduce the serum ammonia levels. Works like a wonder.

According to UpToDate, the recommended dose of lactulose for prevention of recurrent HE is 30 to 45 ml twice or four times daily. Dose may be adjusted every couple of days in order to achieve 2-3 soft stools in a day. For treatment purposes, lactulose syrup of 30-45 ml every 1 to 2 hours can be administered to produce at least 2 stools per day. Subsequently, the frequency can be reduced to twice or four times daily and adjusted as for prevention (UptoDate, 2023). Alternatively, a rectal enema can be used, whereby 300ml of lactulose in 700 ml of normal saline (NS) or water is retained for 30-60 minutes in the rectum. This can be repeated once every 4 to 7 hours, depending on how responsive a patient is to it.

With that, I think it’s safe to say that the title of this article rings true to a certain extent. If you’re wondering whether diabetics can safely consume lactulose for their constipation, fret not, for a study by Pieber et al. found that non-insulin dependent T2DM diabetics need only worry about mild to moderate intensity abdominal distention and flatulence. Fortunately, no unforeseen safety issues arose and there was no concern of their blood glucose management upon consuming the normal recommended dose of  lactulose for constipation (Faerber et al., 2022).

References

1. www.nhsinform.scot. (2023). Constipation symptoms and treatments. [online] Available at: https://www.nhsinform.scot/illnesses-and-conditions/stomach-liver-and-gastrointestinal-tract/constipation#:~:text=Constipation%20usually%20occurs%20when%20stools.
2. Tranah, T.H., Paolino, A. and Shawcross, D.L. (2015). Pathophysiological mechanisms of hepatic encephalopathy. Clinical Liver Disease, 5(3), pp.59–63. doi:https://doi.org/10.1002/cld.445.
3. Faerber, V., Kuhn, K., Svehlikova, E., Kuchinka-Koch, A. and Pieber, T. (2022). Oral Lactulose -A Safe and Effective Strategy for the Management of Constipation in Individuals with Impaired Glucose Tolerance and Diabetes. Gastroenterology Research Commentary 1 Arch Gastroenterol Res, [online] 3(1), pp.1–8. Available at: https://www.scientificarchives.com/public/assets/articles/article-pdf-1663927266-408.pdf [Accessed 1 Jan. 2023].