Principles of Therapy
Treatment should be instituted primarily to obtain regular and complete spontaneous bowel movements to improve quality of life, and secondarily to palliate symptoms of anorexia, bloating, and abdominal pain. The efficacy, safety and drug dependency should all be considered when deciding which laxative to use. Bulk-producing and osmotic laxatives are generally the first choice. Osmotic or stimulant laxatives may be used alone or in combination with bulking agents. Other agents for the management of chronic constipation may be considered after a therapeutic trial of fiber supplementation and laxatives. If pharmacological therapy is ineffective, consider ruling out motility disorder-associated constipation (eg chronic pseudo-intestinal obstruction, rectal intussusception) or outlet obstructive constipation.
Pharmacological therapy
Bulk-Producing Laxatives
Example drugs: Calcium polycarbophil, Ispaghula (Psyllium), Methylcellulose, Sterculia
Bulk-producing laxatives increase the volume of stool and increase GI motility. Psyllium has been shown to increase stool frequency and improve stool consistency in patients with chronic constipation. Therapy should be started with two daily doses in the morning and evening with fluids; the dose may be adjusted after 7-10 days. Patients should be informed that an immediate response should not be expected and that bloating and abdominal distension may occur, especially at the start of fiber therapy, but may decrease over time or with a dose reduction.
Osmotic Laxatives
Example drugs: Lactitol, Lactulose, Macrogol/Polyethylene glycol (PEG), Milk of Magnesia, Sodium chloride, Sodium phosphate, Sorbitol
Osmotic laxatives are poorly absorbed or non-absorbed substances that cause secretion of water into the intestines osmotically increasing intraluminal fluids that ease transport of colonic content. Osmotic laxatives may be attempted if an increase in fiber or use of bulk-producing laxatives fails to relieve symptoms. Non-absorbable carbohydrates (eg Lactitol, Lactulose and Sorbitol) can be used safely for the long-term and in special cases (eg elderly patients, pregnant and lactating women, and patients with DM or chronic kidney disease). Lactulose has been shown to be effective at increasing stool frequency and stool consistency in patients with chronic constipation. This may have a prebiotic effect (ie growth of colonic probiotic bacteria is supported) that could bring about bowel function improvement.
Polyethylene glycol has been demonstrated in a Cochrane analysis to be superior to Lactulose in patients with chronic constipation. It is not metabolized or absorbed and its effect is increased with an increase in dose. It is also effective for fecal impaction in the elderly and pregnant women and is safe for long-term use.
Constipation in Adults_Management 1Combination therapy may also be considered with either a stimulant or an enterokinetic agent (eg Prucalopride) plus an osmotic agent. Patients may be instructed to adjust the dose so that soft, but not liquid stools are achieved and that these agents may take several days to work. Hypermagnesemia may result from high intake of magnesium salts in patients with renal function impairment. It is recommended to perform periodic measurements of serum magnesium level.
Stimulant Laxatives
Example drugs: Bisacodyl, Glycerin, Senna, Sodium picosulfate
Constipation in Adults_Management 2Stimulant laxatives are active metabolites that have both secretory and anti-absorptive effects, increasing intestinal motility. Glycerin or Bisacodyl suppository cause local rectal stimulation thus inducing defecation. These are used as rescue or short-term therapy in patients who are unresponsive to bulk-producing and/or osmotic laxatives due to concerns about long-term safety and abuse. These work within a few hours but may cause abdominal cramps, watery diarrhea and dehydration. Bisacodyl and Sodium picosulfate may be used as rescue therapy in combination with other treatment agents for chronic idiopathic constipation. Short-term use of Senna is considered safe during pregnancy and no increased risk of congenital abnormalities was observed with its use during pregnancy. Long-term (ie >4 weeks) oral use of stimulant laxatives should be avoided.
Other Agents for Constipation
Ileal Bile Acid Transporter Inhibitor
Example drug: Elobixibat
An ileal bile acid transporter inhibitor enhances bile acid supply in the proximal colon, where it induces secretory and motor effects. The efficacy has been investigated in older adults and patients with cancer and chronic renal failure.
Probiotics
Constipation in Adults_Management 3Bifidobacteria, Lactobacilli and Streptococci strains, alone or in combination, increase colonic transit time and stool frequency and improve stool consistency in patients with functional constipation. These inhibit pathogenic bacteria invasion of the GI tract and have immune-modulating potential and anti-inflammatory properties. Synbiotics are a mixture of probiotics and prebiotics (eg inulin, oligosaccharides, Lactulose) with demonstrated beneficial effects in patients with constipation. Adjunctive use of probiotics and synbiotics appears promising; however, further studies are needed prior to recommending a specific probiotic strain or preparation for the treatment of functional constipation.
Prokinetic Agent
Example drug: Prucalopride
A prokinetic agent is a selective serotonin (5-hydroxytryptamine [5-HT4]) receptor agonist that accelerates colonic transit time in patients with slow transit constipation. This is effective in patients with severe chronic constipation refractory to conventional laxatives. This can also be used as an adjunct to over-the-counter agents. This has demonstrated no significant adverse cardiac side effects in large trials. This may be given to elderly patients and those with stable cardiovascular disease.
Secretagogues
Example drugs: Linaclotide, Lubiprostone, Plecanatide
Secretagogues stimulate chloride and fluid secretion into the intestinal lumen, accelerating small bowel and colon transit. These can be used as an alternative or as an adjunct to over-the-counter agents. These agents have no arrhythmic effects.
Other Laxatives
Stool softeners (eg Docusate sodium) are typically used in combination with bulk-forming and stimulant laxatives. Lubricants (eg Mineral oil) may also be used.
Enemas
Constipation in Adults_Management 4Enemas distend the colon, thus inducing stool evacuation. These aid in the treatment of fecal impaction. A cleansing enema or short-term stimulant laxative can be used to relieve symptoms. Bulk-producing or osmotic laxatives may then be used to maintain bowel patency. These may be considered in patients who have failed all other treatment measures (ie refractory defecatory disorders). Avoid in patients at risk of fluid or electrolyte imbalance (eg individuals with cardiac or renal disease, elderly).
Nonpharmacological
Dietary Modification1
Constipation in Adults_Management 5
Patients should be advised to gradually increase their soluble dietary fiber. If possible, dietary fiber via fruits, vegetables, legumes and whole grains should be increased to 20-30 g/day. If this is not effective, commercial soluble fiber supplements (eg bulk-producing laxatives, Maltodextrin) may be added. Insoluble fibers (eg bran, rye bread, lignin) may aggravate constipation-related symptoms such as flatulence and abdominal distention in patients with slow transit constipation or defecatory disorders. Patients may be encouraged to maintain adequate hydration (2-2.5 L/day), though increased fluid intake does not appear to relieve chronic constipation except in those who are dehydrated. Estimate the caloric intake, as caloric restriction may result in constipation.
1Nutritional products for the dietary management of constipation are available. Please see the latest MIMS for specific formulations and prescribing information.
Patient Education
Constipation in Adults_Management 6
Engage in regular exercise and physical activity. Inform the patient that therapy is comprehensive in order to restore the defecation physiology. Reassure and explain normal bowel habits and routine toileting. Encourage patients to defecate when colonic activity is highest (eg upon waking, after meals). Advise the patient to consider reducing or stopping intake of constipating food and medications if possible. Inform the patient regarding appropriate use of other options for bowel cleansing, such as disimpaction and retrograde bowel irrigation.
Surgery
A surgical referral may be considered for treatment of constipation (evacuation disorder, slow transit constipation) if the patient is unresponsive after a prolonged trial of non-surgical measures, is without defecatory disorders or other GI motility disorders, and if symptoms affect activities of daily living. Effective in relieving constipation is a subtotal colectomy with ileorectostomy with a laparoscopic colectomy obtaining a similar success rate but less morbidity than an open colectomy. A rectovaginal repair or rectal suspension may be considered for a rectocele or rectal prolapse. Antegrade continence enema is an effective surgical option for managing constipation in cases where conservative treatments are ineffective or difficult to continue, helping to prevent the need for a colostomy or colon resection. Patients with functional constipation should have a formal psychiatric and upper GI motility evaluation with small intestine transit time measurement before undergoing surgery.