Chapter 79: Laxatives

Senna (Senokot, Ex-Lax)

*Classification:* Stimulant Laxactive (Group II: Produce Semifluid Stool in 6-12 Hr) *Mechanism of Action:* plant-derived laxative that contains anthraquinones as active ingredients. The actions and applications of senna are similar to those of bisacodyl. Anthraquinones act on the colon to produce a soft or semifluid stool in 6 to 12 hours. *Therapeutic Uses:* *Facts:* -Systemic absorption followed by renal secretion may impart a harmless yellowish-brown or pink color to the urine. *Adverse Effects:* harmless yellowish-brown or pink color to the urine. *Patient Teaching:* Inform patients that senna can impart a harmless yellowish-brown or pink color to urine. *Assessment:*

Glycerin Suppository

*Mechanism of Action:* Glycerin is an osmotic agent that softens and lubricates inspissated (hardened, impacted) feces. The drug may also stimulate rectal contraction. Evacuation occurs about 30 minutes after suppository insertion. *Therapeutic Uses:* Glycerin suppositories have been useful for reestablishing normal bowel function following termination of chronic laxative use. *Facts:* *Adverse Effects:* *Patient Teaching:* *Assessment:*

Bowel-Cleansing Products for Colonoscopy

Colonoscopy is the most effective method for early detection of colorectal cancer, the second leading cause of cancer deaths in the United States. Before the procedure, the bowel must be cleansed to permit good visualization. Three kinds of bowel cleansers are used: (1) sodium phosphate (2) a combination of sodium picosulfate, magnesium oxide, and citric acid (3) PEG plus electrolytes (ELS) -The PEG-ELS products are isotonic with body fluids, and hence *do not alter water or electrolyte status*. -In contrast, the sodium phosphate and combination products are hypertonic and *can cause dehydration and electrolyte disturbances*. -In addition, the *sodium phosphate products can cause kidney damage*. However, despite their greater potential for harm, the *sodium phosphate products have better patient acceptance* because the PEG-ELS products require ingestion of a large volume of liquid, whereas the sodium phosphate products do not. -Nonetheless, *sodium phosphate products should be avoided by patients at risk*, including those with electrolyte abnormalities, renal impairment, and hypovolemia.

Precautions and Contraindications to Laxative Use

Laxatives are contraindicated for individuals with certain disorders of the bowel. Specifically, laxatives must be avoided by individuals experiencing abdominal pain, nausea, cramps, or other symptoms of appendicitis, regional enteritis, diverticulitis, and ulcerative colitis. Laxatives are also contraindicated for patients with acute surgical abdomen. In addition, laxatives should not be used in patients with fecal impaction or obstruction of the bowel, because increased peristalsis could cause bowel perforation. Lastly, laxatives should not be employed habitually to manage constipation. *Laxatives should be used with caution during pregnancy (because GI stimulation might induce labor) and during lactation (because the laxative may be excreted in breast milk).*

Reducing Laxative Abuse

Patient education is a key factor in reducing laxative abuse. Educate patients about normal bowel function to correct misconceptions. Provide instruction on establishing good bowel habits (heeding the defecatory reflex, establishing a consistent time for bowel movements). Advise patients to exercise—especially after meals—and to increase consumption of fluids and fiber (bran, fruits, vegetables). Inform patients that laxatives should be used only when clearly necessary and then only briefly in the lowest effective dosage. Warn patients against using cathartics.

Four Major Categories of Laxatives:

(1) bulk-forming laxatives (2) surfactant laxatives (3) stimulant laxatives (4) osmotic laxatives

Lactulose (Constulose, Enulose)

*Classification:* Osmotic Laxative (Laxative Salts) *Mechanism of Action:* Lactulose is poorly absorbed and cannot be digested by intestinal enzymes. In the colon, resident bacteria metabolize lactulose to lactic acid, formic acid, and acetic acid. These acids exert a mild osmotic action, producing a soft, formed stool in 1 to 3 days. *Therapeutic Uses:* -In addition to its *laxative action*, lactulose can enhance *intestinal excretion of ammonia*. This property has been exploited to lower blood ammonia content in patients with portal hypertension and hepatic encephalopathy secondary to chronic liver disease. *Facts:* -reserved for patients who do not respond adequately to a bulk-forming agent -although lactulose can relieve constipation, this agent is more expensive than equivalent drugs (bulk-forming laxatives), and causes more unpleasant side effects (flatulence and cramping are common) *Adverse Effects:* -flatulence and cramping are common *Patient Teaching:* *Assessment:*

Polyethylene Glycol (PEG) (MiraLax, GlycoLax, Peglax)

*Classification:* Osmotic Laxative (Laxative Salts) *Mechanism of Action:* Like the laxative salts, PEG is a nonabsorbable compound that retains water in the intestinal lumen, causing the fecal mass to soften and swell. *Therapeutic Uses:* -is an osmotic laxative used widely for *chronic constipation* -products that contain PEG plus electrolytes can be used to cleanse the bowel before *colonoscopy and other procedures* *Facts:* *Adverse Effects:* -most common adverse effects are *nausea, abdominal bloating, cramping, and flatulence*. -high doses may cause *diarrhea*. *Patient Teaching:* -The recommended dosage is 17 gm once a day, dissolved in 4 to 8 ounces of water, juice, soda, coffee, or tea. -Bowel movement may not occur for another 2 to 4 days. *Assessment:*

Lubiprostone (Amitiza)

*Classification:* Selective Chloride Channel Activators *Mechanism of Action:* By activating (opening) chloride channels in epithelial cells lining the intestine, lubiprostone (1) promotes secretion of chloride-rich fluid into the intestine (2) enhances motility in the small intestine and colon -The result is spontaneous evacuation of a semisoft stool, usually within 24 hours. *Therapeutic Uses:* Lubiprostone has three indications: (1) *chronic idiopathic constipation* in adults (2) *irritable bowel syndrome with constipation* (IBS-C) in women at least 18 years old (3) treatment of *opioid-induced constipation* in chronic noncancer pain. -In clinical trials, the drug reduced *constipation severity, abdominal bloating, and discomfort*. *Facts:* -first representative of a new class of drugs: the selective chloride channel activators. -taken orally, and very little is absorbed *Adverse Effects:* -Nausea -GI effects include *diarrhea, abdominal distention, abdominal pain, gas, vomiting, and loose stools* -Headache -small percentage of patients experience difficulty breathing in association with a sense of tightness in the chest, starting 30 to 60 minutes after the first dose and resolving in a few hours -Pregnancy Risk Category C: Fetal loss *Patient Teaching:* -Nausea is the most common side effect and can be reduced by taking lubiprostone with food and water. -Drug should be taken with food and water. *Assessment:*

Castor Oil

*Classification:* Stimulant Laxative *Mechanism of Action:* -only stimulant laxative that acts on the small intestine. -drug acts quickly (in 2 to 6 hours) to produce a watery stool. Hence, unlike other stimulant laxatives, which are all group II agents, castor oil belongs to group I. *Therapeutic Uses:* limited to situations in which rapid and thorough evacuation of the bowel is desired (eg, preparation for radiologic procedures) *Facts:* -drug is far too powerful for routine treatment of constipation *Adverse Effects:* *Patient Teaching:* -should not be administered at bedtime -drug has an unpleasant taste that can be improved by chilling and mixing with fruit juice. -it is a powerful laxative and should not be used to treat routine constipation *Assessment:*

Bisacodyl (Correctol, Dulcolax)

*Classification:* Stimulant Laxatives (Group II: Produce Semifluid Stool in 6-12 Hr) *Mechanism of Action:* (1) Stimulate peristalsis (2) soften feces by increasing secretion of water and electrolytes into the intestine and decreasing water and electrolyte absorption -Site of action: Colon *Therapeutic Uses:* *Facts:* -Administered by rectal suppository as well as by mouth. -Oral bisacodyl acts within 6 to 12 hours. Hence, tablets may be given at bedtime to produce a response the following morning. -Bisacodyl suppositories act rapidly (in 15 to 60 minutes) *Adverse Effects:* Bisacodyl suppositories may cause a *burning sensation* and, with continued use, *proctitis* may develop. *Patient Teaching:* Bisacodyl tablets are enteric coated to prevent gastric irritation. Accordingly, patients should be advised to swallow them intact, without chewing or crushing. Because milk and antacids accelerate dissolution of the enteric coating, the tablets should be administered no sooner than 1 hour after ingesting these substances. Accordingly, long-term use should be discouraged. & Tell them about the adverse effect. *Assessment:*

Surfactant Laxatives

*Mechanism of Action:* -Surfactants alter stool consistency by lowering surface tension, which facilitates penetration of water into the feces. -The surfactants may also act on the intestinal wall to (1) inhibit fluid absorption (2) stimulate secretion of water and electrolytes into the intestinal lumen -In this respect, *surfactants resemble the stimulant laxatives* *Therapeutic Uses:* The surfactants (eg, docusate sodium) are group III laxatives: They produce a soft stool several days after the onset of treatment *Facts:* *Adverse Effects:* *Patient Teaching:* Administration should be accompanied by a full glass of water. *Assessment:*

Osmotic Laxatives

*Mechanism of Action:* The laxative salts (eg, sodium phosphate, magnesium hydroxide) are poorly absorbed salts whose osmotic action draws water into the intestinal lumen. Accumulation of water causes the fecal mass to soften and swell, thereby stretching the intestinal wall, which stimulates peristalsis. *Therapeutic Uses:* --When administered in low doses, the osmotic laxatives produce a *soft or semifluid stool* in 6 to 12 hours. -High-dose therapy is employed to empty the bowel in preparation for *diagnostic and surgical procedures*. -High doses are also employed to purge the bowel of *ingested poisons, and to evacuate dead parasites following anthelmintic therapy*. *Facts:* -poorly and slowly absorbed, some absorption does take place. *Adverse Effects:* -can cause substantial loss of water -In patients with renal impairment, *magnesium* can accumulate to toxic levels. -*Sodium phosphate* can also cause *acute renal failure* in vulnerable patients, especially those with kidney disease and those taking drugs that alter renal function (eg, diuretics, angiotensin-converting enzyme [ACE] inhibitors, angiotensin receptor blockers [ARBs]) *Patient Teaching:* -To avoid dehydration, patients should increase fluid intake. -*Magnesium salts* are contraindicated in patients with kidney disease. -Sodium absorption (from *sodium phosphate*) can cause fluid retention, which in turn can exacerbate heart failure, hypertension, and edema. Accordingly, sodium phosphate is contraindicated for patients with these disorders. *Assessment:* -Renal Function -Magnesium Levels

Stimulant Laxactives

*Mechanism of Action:* Have two effects on the bowel. -First, they stimulate intestinal motility—hence their name. -Second, they increase the amount of water and electrolytes within the intestinal lumen by increasing secretion of water and ions into the intestine, and by reducing water and electrolyte absorption. *Therapeutic Uses:* -treatment of opioid-induced constipation -treatment of constipation resulting from slow intestinal transit *Facts:* -Stimulant laxatives are widely used—and abused—by the general public, and are of concern for this reason. -Most stimulant laxatives are group II agents: They act on the colon to produce a semifluid stool within 6 to 12 hours. *Adverse Effects:* *Patient Teaching:* Discourage patients from inappropriate use of these drugs. *Assessment:*

Mineral Oil

*Mechanism of Action:* Mineral oil is a mixture of indigestible and poorly absorbed hydrocarbons. Laxative action is produced by lubrication. *Therapeutic Uses:* -Mineral oil is especially useful when administered by enema to treat fecal impaction. *Facts:* *Adverse Effects:* Mineral oil can produce a variety of adverse effects. Aspiration of oil droplets can cause lipid pneumonia. Anal leakage can cause pruritus and soiling. Systemic absorption can produce deposition of mineral oil in the liver. Excessive dosing can decrease absorption of fat-soluble vitamins. *Patient Teaching:* *Assessment:*

Polyethylene Glycol-Electrolyte Solutions

*Mechanism of Action:* These bowel-cleansing solutions [CoLyte, GoLYTELY, others] contain PEG, a nonabsorbable osmotic agent, together with ELS (usually potassium chloride, sodium chloride, sodium sulfate, and sodium bicarbonate). The mixture is isosmotic with body fluids, and hence water and electrolytes are neither absorbed from nor secreted into the intestinal lumen. As a result, dehydration does not occur and electrolyte balance is preserved. Because effects on water and electrolytes are minimal, PEG-ELS solutions can be used safely by patients who are dehydrated and by those who are especially sensitive to alteration of electrolyte levels (eg, patients with renal impairment or cardiovascular disease). *Therapeutic Uses:* *Facts:* -Because PEG-ELS products don't alter water and electrolyte status, they are safer than sodium phosphate products for patients with electrolyte imbalances, heart failure, kidney disease, or advanced liver disease. -generally well tolerated -Patients have to drink so much fluid that they will prefer sodium phosphate even if it has more harmful adverse effects. *Adverse Effects:* -*nausea, bloating, and abdominal discomfort* *Patient Teaching:* *Assessment:*

Bulk-Forming Laxatives

*Mechanism of Action:* have actions and effects much like those of dietary fiber (fiber makes you poop) *Therapeutic Uses:* -Bulk-forming laxatives are preferred agents for *temporary treatment of constipation*. -Also, they are widely used in patients with *diverticulosis and irritable bowel syndrome*. -In addition, by altering fecal consistency, they can provide *symptomatic relief of diarrhea and can reduce discomfort and inconvenience for patients with an ileostomy or colostomy*. *Facts:* -bulk-forming agents belong to our therapeutic group III, producing a soft, formed stool after 1 to 3 days of use -should be administered with a full glass of water or juice to prevent esophageal obstruction *Adverse Effects:* -not absorbed, systemic reactions are rare. -*Esophageal obstruction* can occur if they are swallowed in the absence of sufficient fluid. -If their passage through the intestine is impeded, they may produce *intestinal obstruction or impaction*. -Accordingly, they should be avoided if there is *narrowing of the intestinal lumen*. *Patient Teaching:* All drug under this category: Psyllium, methylcellulose, and polycarbophil should be administered with a full glass of water or juice. *Assessment:* Uses for this group include treating chronic constipation and preventing straining at stool.

Sodium Phosphate Products

*Mechanism of Action:* sodium phosphate is an osmotic laxative that draws water into the intestinal lumen, which then softens and swells the fecal mass, which then stretches the intestinal wall to stimulate peristalsis. *Therapeutic Uses:* *Facts:* -drink water or clear liquid to swallow pill -more appealing than PEG-ELS solutions, although more harmful *Adverse Effects:* -(Like PEG-ELS products) *nausea, bloating, and abdominal discomfort*. -(Different from PEG-ELS products) especially *dehydration, electrolyte disturbances, and kidney damage*. By drawing a large volume of fluid into the intestinal lumen, sodium phosphate can cause *dehydration*. -Rarely, phosphate is absorbed in amounts sufficient to cause hyperphosphatemia, which can cause acute, reversible renal damage, and possibly chronic, irreversible renal damage. Risk factors for hyperphosphatemia and kidney damage include hypovolemia, advanced age, delayed bowel transit, active colitis, preexisting kidney disease, and use of drugs that can alter kidney function, including diuretics, ACE inhibitors, ARBs, and nonsteroidal antiinflammatory drugs. Patients who have these risk factors should probably use a PEG-ELS product rather than sodium phosphate. *Patient Teaching:* To prevent dehydration, patients must drink a large volume of clear fluid before, during, and after dosing. *Assessment:*

Classification of Laxatives

-*Group I* agents act rapidly (within 2 to 6 hours) and give a watery consistency to the stool. Laxatives in group I are especially useful when preparing the bowel for diagnostic procedures or surgery. -*Group II* agents have an intermediate latency (6 to 12 hours) and produce a stool that is semifluid. Group II agents are the ones most frequently abused by the general public. -*Group III* laxatives act slowly (in 1 to 3 days) to produce a soft but formed stool. Uses for this group include treating chronic constipation and preventing straining at stool.

Indications for Laxative Use

Laxatives can be highly beneficial when employed for valid indications. By softening the stool, laxatives can reduce the painful elimination that can be associated with episiotomy and with hemorrhoids and other anorectal lesions. -In patients with cardiovascular diseases (eg, aneurysm, myocardial infarction, disease of the cerebral or cardiac vasculature), softening the stool decreases the amount of strain needed to defecate, avoiding dangerous elevation of blood pressure. -In older-adult patients, laxatives can help compensate for loss of tone in abdominal and perineal muscles. -As an *adjunct to anthelmintic therapy*, laxatives can be used for (1) obtaining a fresh stool sample for diagnosis (2) emptying the bowel before treatment (so as to increase parasitic exposure to anthelmintic medication) (3) facilitating export of dead parasites following anthelmintic use. -Additional applications include (1) emptying of the bowel before surgery and diagnostic procedures (eg, radiologic examination, colonoscopy) (2) modifying the effluent from an ileostomy or colostomy (3) preventing fecal impaction in bedridden patients (4) removing ingested poisons (5) correcting constipation associated with pregnancy and certain drugs, especially opioid analgesics

Combination Products

One combination product—magnesium oxide/anhydrous citric acid/sodium picosulfate [Prepopik]—is approved for preparation for colonoscopy in adults. Sodium picosulfate is a stimulant laxative, and magnesium oxide and citric acid combine to form magnesium citrate, an osmotic laxative. When given in a split-dose regimen, results were superior to colon preparation with PEG-ELS. Prepopik is given in a split-dose regimen. It is supplied in 2 packets containing 16.1 gm each of powder that must be mixed with water for consumption. The first dose is taken the evening before the colonoscopy and the second dose the next morning before the procedure. As with sodium phosphate products, Prepopik can cause electrolyte and fluid imbalances, renal impairment, seizures, and dysrhythmia secondary to electrolyte abnormalities. Caution must be employed in patients with reduced renal function. The most common adverse reactions are nausea, headache, and vomiting.