Laxatives and oral bowel

Mannitol is an osmotic diuretic that has been used in acute oliguric renal insufficiency, acute cerebral edema, and the short-term management of glaucoma, especially to reduce intraocular pressure before ophthalmic surgery. Other indications include promotion of the excretion of toxic substances by forced diuresis, bladder irrigation during transurethral resection of the prostate, and oral administration as an osmotic laxative for bowel preparation. Mannitol is used as a diluent and excipient in pharmaceutical formulations and as a bulk sweetener. 

The Austrian Adverse Drug Reactions Advisory Committee received three reports of severe electroljde disturbances associated with an oral bowel-cleansing solution containing sodium phosphate solution (Fleet Phospho-Soda Buffered Saline Laxative Mixture), used as a bowel preparation for colonoscopy (5). Prescribers are advised to be aware of complications of the use of phosphate enemas, particularly in infants, elderly or debilitated patients, patients with congestive heart failure, and patients with impaired renal function. 

Long-term use of oral opiates is not routinely recommended for several pharmacologic reasons. Some opioids such as morphine and codeine have the tendency to cause constipation by slowing down the peristaltic action of the bowels, which can also result in a functional ileus. This effect can be minimized by administering laxatives and/or stool softeners in patients who require longer-term opiate therapy. Prokinetic agents may also be helpful in treating opiate-related constipation. 

In the hospitalized patient without 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. For prompt initiation of a bowel movement, a tap-water enema or glycerin suppository is recommended, or milk of magnesia. 

Laxative effect. Seed hull, taken orally by adults at a dose of 7 g/person, increased weekly fecal mass without influencing transit time or frequency . Seedcoat, administered orally to 80 patients at a dose of 6.4 g/person three times daily, was active in a blinded placebo controlled study of efficacy of extract in treatment of irritable bowel syndrome " . Water extract of the dried kernel, administered orally to 40-year-old adults of both sexes, was active . Seed powder, administered orally to adults of both sexes, was active. Biological activity reported has been patented ". Dried seeds, administered orally to adults at a dose of 0.5 g/person, were active. Placing the seeds in water increased their volume, 90% alcohol produced a decrease in volume to normal seed size, and linseed oil had no effect on volume. The seed mucilage remained in gel form and is considered preferable to the solid form because it is more easily digested " . Dried seed powder, administered orally to 35 patients with chronic constipation at a dose of 50 mg/person, was active in a controlled, double-blind study " . Fiber, administered orally to adults, was active. Psyllium fiber and sennosides were prepared into a wafer to be... 

Aloe, senna, and cascara occur naturally in plants. These laxatives are poorly absorbed and after hydrolysis in the colon, produce a bowel movement in 6-12 hours when given orally and within 2 hours when given rectally. Chronic use leads to a characteristic brown pigmentation of the colon known as melanosis coli. There has been some concern that these agents may be carcinogenic, but epidemiologic studies do not suggest a relation to colorectal cancer. 

Niclosamide [ni KLOE sa mide] is the drug of choice for most ces-tode (tapeworm) infections. Its action has been ascribed to inhibition of the parasite s mitochondrial anaerobic phosphorylation of ADP which produces usable energy in the form of ATP. The drug is lethal for the cestode s scolex and segments of cestodes but not for the ova. A laxative is administered prior to oral administration of niclosamide. This is done to purge the bowel of all dead segments in order to preclude digestion and liberation of the ova, which may lead to cysticercosis. Alcohol should be avoided within 1 day of niclosamide. 

Sorbitol is slowly absorbed by passive diffusion in the small intestine. After oral administration, it increases osmotic pressure in the bowel by drawing in water, and is thus an osmotic laxative, sometimes leading to diarrhea... 

Sodium phosphates are considered to be dangerous (1), particularly because of their effects on electrolyte balance. An oral solution of sodium phosphates (dibasic sodium phosphate + monobasic sodium phosphate) is used as a laxative for the relief of occasional constipation and is used as part of a bowel-cleansing regimen in preparing patients for surgery or colonoscopy. 

Oral administration of large quantities of polyethylene glycols can have a laxative effect. Therapeutically, up to 4 L of an aqueous mixture of electrolytes and high-molecular-weight polyethylene glycol is consumed by patients undergoing bowel cleansing. 

Data in humans and animals suggest that acute oral exposures to sulfate exert a laxative effect (loose stool) and sometimes diarrhea (unusually frequent or unusually liquid bowel movements) following exposures to high concentrations. However, these effects are not observed for longer-term exposures. This may be because of acclimation to sulfate over time. 

Bisacodyl is a laxative that is indicated in short-term treatment of constipation evacuation of colon for rectal and bowel evaluation preparation for delivery or surgery. Bisacodyl is the only diphenyhnethane derivative available in the United States. It is marketed as an enteric-coated preparation (Dulcolax, Correctol, others) and as a suppository for rectal administration. The usual oral daily dose of bisacodyl is 10 to 15 mg for adults and 5 to 10 mg for children 6 to 12 years old. The drug requires hydrolysis by endogenous esterases in the bowel for activation, and so the laxative effects after an oral dose usually are not produced in less than 6 hours taken at bedtime, it will produce its effect the next morning. Suppositories work much more rapidly. 

Patient education should include information about dietary sources of calcium, the need to maintain physical activity to avoid bone loss, avoid ovemse of antacids, and chronic use of laxatives. Patients should be taught to use fruits and fiber for improving bowel elimination. Take oral supplements with meals or after meals to increase absorption. 

The lack of vitamin C effect on incidence of colds in the studies analyzed by Hemila (1994) may be related to the small amount of vitamin tested (Pauling, 1986). Thus, Cathcart has found that the maximum concentration of vitamin C tolerated by persons increases with illness and severity of disease. Based on initial observations made with 9000 patients who had been treated with large doses of vitamin C, Cathcart (1981) reported that while healthy persons can tolerate oral intakes from 4-15 g per day, their bowel-tolerance level—the amount slightly lower than that which produces a laxative effect—increased to values of 30-60 g during a mild cold, 60-100 g during a severe cold, and greater than 100 g during an attack of influenza or flu. In cases of severe viral illnesses such as infectious mononucleosis or pneumonia, the bowel-tolerance doses were found to approach 200 g per day. Cathcart found that vitamin C therapy for the common cold and infectious diseases was most effective when administered at the bowel-tolerance dose. Upon control of... 

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