My wife and I walk our Goldendoodle at least 3–4 times a day, no matter the weather. Maybe I am weird, but I praise my dog for peeing and pooping. When it comes to the rest of us humans, we feel embarrassed to mention constipation or diarrhea. It is embarrassing and sometimes painful. We may also have to spend a lot of time in the bathroom, trying to nip the problem in the bud as soon as possible.
The American Gastroenterological Association (AGA) defines constipation as infrequent bowel movements (typically fewer than 3 per week), difficulty passing stools, hard or lumpy stools, and a sensation of incomplete evacuation. Constipation is a syndrome, not a disease. It can be a primary GI issue or secondary to a preexisting disorder, such as irritable bowel syndrome with constipation (IBS-C). In my experience in hospital and outpatient settings, medications can be the culprit in constipation (e.g., opioids). Chronic idiopathic constipation (CIC) affects 9%–20% of adults in the United States (Am J Gastroenterol. 2020 Apr 23;115(6):895–905).
Constipation is a quality-of-life issue. Risk factors that cannot be modified by medications or diet include female gender. Women are more than twice as likely as men to develop CIC (American Family Physician, 2022;106(3):299-306). Older age significantly increases the risk, especially among adults 65 and older or those living in nursing homes. When I worked as a pharmacist at five nursing homes, the residents’ most common complaint was difficulty with regular bowel movements. Pre-existing medical conditions, such as IBS-C and colonic dysfunction, increase the risk of constipation.
A first-line, OTC treatment for CIC is polyethylene glycol (PEG), sold under the trade name MiraLAX. PEG can also be used with a bulk laxative. PEG is typically taken daily as a powder and acts as an osmotic laxative. Osmotic laxatives draw water into the colon, hydrating the stool and increasing transit time to the anus. PEG has moderate evidence of long-term efficacy and safety. PEG is also available in gummy form. PEG can take 1–3 days to take effect. If you have ever had a colonoscopy, you are probably familiar with PEG as a bowel prep. Side effects of PEG include bloating, loose stools, flatulence, and nausea. Magnesium oxide supplements are osmotic laxatives and have been found to soften stool and increase the frequency of bowel movements. Magnesium oxide supplements should be taken at night and will take 6–12 hours to start working.
Bisacodyl (Dulcolax) can be used for short-term (< 4 weeks) constipation. It is available as a tablet or suppository. Bisacodyl is a colon irritant that stimulates the large-intestine mucosa, increasing colonic peristalsis (movement) and promoting the accumulation of water and electrolytes. This stimulates defecation, reduces transit time, and softens the stool. Psyllium (Metamucil) is a bulk-forming laxative and is recommended as first-line for mild constipation only. Senna is an over-the-counter stimulant laxative used to treat occasional constipation by triggering intestinal muscles to push stool out, typically producing a bowel movement within 6 to 12 hours. Senna is available in tablets, tea, chewables, liquids, syrups, and capsules. Senna is cost-effective, easy to take, and works well. Every cancer or surgical patient I saw in the hospital who was receiving opioids for pain received senna to prevent constipation. There is also grandma’s favorite laxative, castor oil. Castor oil binds to the smooth muscle of the intestines, causing the intestinal muscles to contract and push stool through the colon. Castor oil usually works in 6 to 12 hours. You must chill the castor oil in the refrigerator and mix it with orange juice. Common side effects include abdominal cramping, nausea, vomiting, and diarrhea.Bisacodyl (Dulcolax) can be used for short-term (< 4 weeks) constipation. It is available as a tablet or suppository. Bisacodyl is a colon irritant that stimulates the large-intestine mucosa, increasing colonic peristalsis (movement) and promoting the accumulation of water and electrolytes. This stimulates defecation, reduces transit time, and softens the stool. Psyllium (Metamucil) is a bulk-forming laxative and is recommended as first-line for mild constipation only. Senna is an over-the-counter stimulant laxative used to treat occasional constipation by triggering intestinal muscles to push stool out, typically producing a bowel movement within 6 to 12 hours. Senna is available in tablets, tea, chewables, liquids, syrups, and capsules. Senna is cost-effective, easy to take, and works well. Every cancer or surgical patient I saw in the hospital who was receiving opioids for pain received senna to prevent constipation. There is also grandma’s favorite laxative, castor oil. Castor oil binds to the smooth muscle of the intestines, causing the intestinal muscles to contract and push stool through the colon. Castor oil usually works in 6 to 12 hours. You must chill the castor oil in the refrigerator and mix it with orange juice. Common side effects include abdominal cramping, nausea, vomiting, and diarrhea.
Another category of prescription-only laxatives is secretagogues. Linaclotide (Linzess) binds to the lining of the small and large intestines, stimulating the release of chloride and bicarbonate, which draws water into the gut. This action softens hard stool and helps move it through the bowel more quickly. Linaclotide also helps reduce abdominal pain, cramping, and bloating. It is prescribed for CIC associated with IBS-C. An AME can issue a CACI if qualified, provided there is a detailed clinical progress note (DCPN) from the treating physician and no side effects.
Docusate sodium (Colace) is an emollient laxative, also known as a stool softener. It lowers the stool’s surface tension, allowing water and fats to penetrate and soften hardened stool. Colace acts like a detergent, mixing water and natural oils in the stool. The onset of action for docusate sodium is 12 to 72 hours. Hydration is the most important factor for docusate to work. With each dose of docusate, you must drink 8 ounces of water, milk, or fruit juice. The total daily fluid intake when taking docusate is 64 ounces.
There are 3 types of diarrhea, namely secretory, osmotic, and inflammatory. Secretory diarrhea is a watery form caused by abnormal secretion of water and electrolytes into the intestine. The intestine becomes so overwhelmed with sodium and water that it cannot reabsorb water back into the body. Common causes of secretory diarrhea include bacterial endotoxins such as cholera or E. coli, as well as bacterial and viral gastroenteritis. I have seen hundreds of cases of bacterial gastroenteritis caused by Clostridium difficile (C. diff.). C. diff. cases are most common in elderly patients who are prescribed proton pump inhibitors (pantoprazole) and have had multiple courses of antibiotics. Patients with C. diff. are treated with oral antibiotics such as metronidazole or vancomycin.
Osmotic diarrhea occurs when salts and glucose accumulate, drawing excess water into the gut and producing watery stools. Causes include carbohydrate malabsorption, excessive intake of sugar alcohols, laxative abuse, and absorptive dysfunction diseases such as celiac disease. Crohn’s disease and ulcerative colitis cause secretory and inflammatory diarrhea. Treatment of osmotic diarrhea is rehydration and OTC antidiarrheals. The OTC antidiarrheals include bismuth subsalicylate (Pepto-Bismol), loperamide (Imodium), psyllium (Metamucil), and diphenoxylate (Lomotil). Of the 5 antidiarrheals recommended, only Lomotil is not allowed for use by the FAA. Bismuth subsalicylate is hydrolyzed to bismuth and salicylic acid. Bismuth and salicylic acid decrease water absorption into the lumen and reduce inflammation. These bismuth salts have bactericidal and antimicrobial activity and prevent bacteria from binding to and growing on stomach mucosal cells. Because of Pepto-Bismol’s bactericidal and antimicrobial activity, it is used to treat traveler’s diarrhea. This mechanism reduces intestinal secretion, promotes fluid absorption, and reduces inflammation. An interesting side effect of Pepto-Bismol is black tongue. Bismuth subsalicylate chemically reacts with the natural sulfur present in your saliva and digestive tract to form a dark substance called bismuth sulfide. Loperamide binds to the opiate receptor in the gut wall. Loperamide inhibits the release of acetylcholine and prostaglandins, reduces propulsive peristalsis (fast movement through the gut), and increases intestinal transit time. Loperamide increases the tone of the anal sphincter, thereby reducing incontinence and urgency.
Lifestyle and dietary measures to reduce the risk of constipation include increasing water intake and dietary fiber. Start with low-dose psyllium supplements and proceed gradually. For diarrhea, the guideline-recommended treatment is oral rehydration with water and electrolytes. Avoid excess caffeine and alcohol, as both worsen loose stools. After rehydration, resume a balanced diet early rather than restricting intake to a strict BRAT (bananas/rice/applesauce/toast) diet.
My hope is that you gain a solid working knowledge of how to treat constipation and diarrhea if they affect you or a loved one. Knowing what triggers these 2 syndromes is most important. Prompt, correct treatment can shorten days of bloating, straining, and abdominal pain with constipation and reduce time spent in the porcelain palace with diarrhea. Be well and fly safe.
