Laxatives and stomach cramps

Types of laxatives

There are four main classes of laxatives:¹

• Osmotic
• Stimulant laxative
• Bulk-forming
• Stool softeners

Osmotic laxatives

Osmotic laxatives are poorly absorbable substances, meaning they pass through the gastrointestinal (GI) tract relatively undigested. They draw water into the intestinal tract, which helps to hydrate, soften, and gently propel fecal matter along the tract. The process by which soluble, non-absorbable substances draw water into the lumen is called osmosis. When used inappropriately, they can cause uncomfortable to severe diarrhea, bloating, abdominal cramping, and, in some cases, significant water loss and dehydration. 

These types of laxatives are most commonly used for cleansing the colon in preparation for a colonoscopy or to remove toxic substances, like in the setting of liver failure (hepatic encephalopathy). For those who take Milk of Magnesia in the setting of kidney disease, the magnesium is partly excreted through the kidneys, so this is not recommended.^1,2,3

Stimulant laxatives

Stimulant laxatives may be prescribed for the treatment of constipation, but this category of laxatives tends to be the most commonly misused form of laxatives due to their rapid onset of action. They stimulate nerve bundles within the intestinal tract, called the Auerbach plexus and myenteric plexus. These nerves control the natural slow-moving muscle contractions that propel food from the mouth to the anus. This smooth muscle contraction is called peristalsis. Stimulant laxatives also decrease how much water is absorbed from food within the lumen of the bowel.¹

They can cause:

• Considerable abdominal pain
• Severe stomach cramps
• Severe nausea
• Vomiting

With treatment that addresses laxative weaning, some symptoms can be resolved, but someone who has misused stimulant laxatives for a long time could struggle with constipation and gut dysmotility permanently.⁷ 

Bulk-forming laxatives

These agents help to retain fluid in the stool and increase stool weight and consistency. Individuals on these types of laxatives need to drink ample amounts of water. Even slight amounts of dehydration can result in bloating, pain, and even a bowel obstruction (where stool becomes completely impacted). Some people do report common side effects like nausea, vomiting, and diarrhea from taking a bulk-forming laxative.¹

Stool softeners

This group includes sodium or calcium salts that act as anionic surfactants. This lowers the surface tension at the oil-water interface of feces, which allows water and fats to better penetrate the stool and mix. This softens fecal matter, making having a bowel movement easier. It is commonly recommended for those who should avoid straining, like after surgery. Because they do not exert stimulant actions, they are not technically considered a laxative. The onset of action takes a bit longer, usually between 1-3 days after ingestion.⁸

There are prescription medications that are not intended primarily for laxative effect but to help an underlying cause of constipation, like chronic slow transit constipation.

Side effects of laxative abuse

The most common medical problems associated with laxative abuse include electrolyte and acid/base changes. Chronic diarrhea causes the body to lose important fluids and electrolytes, which places undue pressure on the heart and kidneys. For those with anorexia nervosa who may already have the beginnings of heart and kidney damage, using laxatives can further exacerbate harm.^1,4,7

When excessive amounts of fluid are lost through diarrhea long term, hormone cascades activate to compensate. If someone abruptly stops using laxatives, the renin-aldosterone hormone system continues to tell the body to hold fluid. This will cause someone to develop significant swelling, called edema. This can make someone feel bloated, which may trigger a return to laxative abuse. They will also likely struggle with painful rebound constipation. The cycle can be difficult to break and should be done with the help of a medical professional.^1,4,7

Treating a laxative habit and misuse

When trying to correct laxative misuse, medical tests, and labs should be performed to check the status of serum electrolytes and acid/base status. After an individual begins treatment to address their eating disorder, a healthcare provider will likely have the person switch to something safer or steadily decrease the dose. This stepwise fashion of carefully withdrawing laxatives helps the body to re-establish normal bowel movements and is the best and safest way to alleviate stomach cramps from laxative abuse.^1,4,7

It can take a few weeks to months to regulate normal bowel cycles again. Recovery is a journey and takes time. If you are struggling to break the cycle of laxative overuse, reaching out for support is an important step toward healing. At Within Health, we educate our clients on what symptoms and side effects to anticipate, so they can heal from laxative abuse and any underlying eating disorders.