Bowel evacuants

Laxatives promote and facilitate bowel evacuation by acting locally to stimulate intestinal peristalsis, to soften bowel contents, or both. 

Misuse of laxatives. It is a widely held belief that at least one bowel movement per day is essential for health yet three bowel evacuations per week are quite normaL The desire for frequent bowel emptying probably stems from the time-honored, albeit... 

Fleet Prep Kit 1, 2, and 3 (Fleet), X-Prep Liquid, X-Prep Bowel Evacuant Kit-1 (Gray), Tridate Bowel Cleansing System (Lafayette)... 

Several studies in infants and children ranging in age from 3 to 14 years of age showed that the use of PEG-electrolyte solutions are safe and effective in bowel evacuation. 

Mechanism of Action A lactose derivative that retains ammonia in colon and decreases serum ammonia concentration, producing osmotic effect. Therapeutic Effect Promotes increased peristalsis and bowel evacuation, which expels ammonia from the colon. 

These inciude phenoiphthaiein and bisacodyl and are effective, but potential toxicity should lead to dosing being iimited to 10 days. Bisacodyl is used for bowel evacuation prior to diagnostic procedures. 

High doses of osmotically active agents produce prompt bowel evacuation (purgation) within 1-3 hours. The rapid movement of water into the distal small bowel and colon leads to a high volume of liquid stool followed by rapid relief of constipation. The most commonly used purgatives are magnesium citrate and sodium phosphate. 

Stimulant laxatives Bisacodyl, 5-15 mg daily. Senna, dosage varies, consult product labeling Correctol, Dulcolax, Ex-Lax, Senokot, various generic Stimulant laxative actions include direct irritation of intestinal mucosa or stimulation of the myenteric plexus, resulting in peristalsis. These agents may also cause alteration of fluid and electrolyte absorption, resulting in luminal fluid accumulation and bowel evacuation. 

Laxatives are typically used whenever normal bowel movements have been impaired but no obstruction exists in the GI system. For instance, laxatives may benefit patients on prolonged bed rest, patients with infrequent or painful bowel movements, patients with spinal cord injuries, or patients who should avoid straining during defecation (e.g., postpartum patients and those recovering from surgical procedures). Laxatives are also indicated for bowel evacuation prior to surgical or diagnostic procedures. 

The problem with laxatives is that they are frequently abused. The long-term, chronic use of laxatives is usually unnecessary and often unhealthy. These agents are self-administered by individuals who are obsessed with maintaining daily bowel movements. The individuals may have the misconception that daily bowel evacuation is needed to maintain normal GI function. Also, laxatives are often relied on instead of other factors that promote normal bowel evacuation, such as a high-fiber diet, adequate hydration, and physical activity.22 Consequently, laxatives serve an important but finite role in GI function, and their role in helping maintain daily evacuation should be deemphasized. 

Disturbances in the GI system, such as nausea and cramps, may occur with laxative use. With prolonged use, serious lower GI irritation, including spastic colitis, may occur. Fluid and electrolyte abnormalities are also a potential problem. Excessive loss of water and the concomitant loss of electrolytes may transpire, resulting in dehydration and possible acid-base imbalances.44 These abnormalities are especially significant in older or debilitated patients. Finally, chronic administration may result in a laxative dependence when bowel evacuation has become so subservient to laxative use that the normal mechanisms governing evacuation and defecation are impaired. 

Quinine has certain minor pharmacological actions quite distinct from its antimalarial role analgesic (in prohibitively high dosage), striated muscle relaxant, and antipyretic. Other uses of quinine are as a sclerosing agent, a bowel evacuant, and in dermatological practice. 

CATHARTICS Promote bowel evacuation, and may be divided into (a) Laxatives, which induce gentle bowel movement and (6) Purgatives, producing copious, repeated, and more watery evacuations (both of which see). 

PURGATIVES Powerful bowel evacuatives.—Bitter Root, Bryony, Mandrake (American). 

Misuse of laxatives. It is a widely held belief that at least one bowel movement per day is essential for health yet three bowel evacuations per week is quite normal. The desire for frequent bowel emptying probably stems from the time-honored, albeit mistaken, notion that absorption of colon contents is harmful. Thus, purging has long been part of standard therapeutic practice. Nowadays it is known that intoxication from intestinal substances is impossible as long as the liver functions normally. Nonetheless, purgatives continue to be sold as remedies to cleanse the blood or to rid the body of corrupt humors. ... 

Saline Sodium biphosphate Magnesium citrate Dibasic sodium Phosphate enemas 0.5-3 Nonabsorbable cations and anions increase osmotic gradient in the gut, drawing in water, causing distention that stimulates peristalsis. Oral phosphate salts contain -96.5 mEq of Na+. Use with caution in Na+-restricted patients. Use only for acute bowel evacuation. 

Bulk producing Psyllium Methyl cellulose 12-72 Adsorbs water in the gut increases stool bulk and moisture, stimulates peristalsis and bowel evacuation Appropriate for long-term, preventative therapy... 

Laxative Osmotic effect primarily in small intestine. Draws water into intestinal lumen, produces distention, promotes peristalsis, bowel evacuation... 

In the hospitalized patient withont GI disease, constipation may be related to the use of general anesthesia and/or opiate substances. Most orally or rectally administered laxatives may be used in these situations. For prompt initiation of bowel evacuation, either a tap-water enema, glycerin suppository, or oral milk of magnesia are recommended. 

The traditional classification system for laxatives and cathartics by suspected mode of action is not very useful, as this is not clearly understood for many agents. In general, most of these products induce bowel evacuation by one or more of the mechanisms associated with the etiology of diarrhea, including active electrolyte secretion, decreased water and electrolyte absorption, increased intraluminal osmolarity, and increased hydrostatic pressnre in the gnt. Laxatives convert the intestine from primarily an organ that absorbs water and electrolytes to an organ that secretes these substances. 

Bowel evacuants are known as bowel cleansing solutions. They are used before surgery or radiological procedures to empty the bowel. They can cause bloating and nausea. Examples are magnesium salts and Picolax and polyethylene glycol. 

Magnesium hydroxide, an antacid with laxative properties (6 to 20 ml/p.o.), is used as an antacid, as a laxative in constipation, and in bowel evacuation before surgery. 

ACUTE HEALTH RISKS may cause irritation to nasal passages irritation to respiratory tract flu-like illness (metal fume fever) may be caused by exposure to freshly formed fumes symptoms of metal fume fever include headache, cough, sweating, chills, fever, aching muscles, nausea, and dryness in mouth and throat may cause rapid bowel evacuation. 

Bulk-forming laxatives are substances that promote bowel evacuation by increasing the bulk volume and water... 

A 62-year-old woman with myelitis and treated with intrathecal baclofen developed vomiting, epigastric pain, and absent peristalsis 7 months after implantation of the intrathecal device. Her last bowel evacuation had occurred 24 days before. She died from complications after surgery. 

But children with VUR, nonneurogenic bladder-sphincter dysfunction and dysfunctional elimination syndromes remain at significant risk for a breakthrough UTI despite antibiotic prophylaxis, anticholinergic therapy, timed voiding and regular bowel evacuation (Koff et al. 1998). 

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