Constipation osmotic laxatives

Polyethylene glycol (PEG, MiraLax) is an osmotic laxative available only by prescription. It is useful in patients who are experiencing acute constipation and who have had inadequate response to more traditional agents. Principal adverse effects include upset stomach, bloating, cramping, and gas. 

Slow-transit constipation can be treated with chronic administration of osmotic laxatives. Tegaserod maleate 6 mg orally twice daily is an acceptable treatment. Senna, bisacodyl, and other stimulants should be used only when the others fail to deliver the desired effect. 

Bisacodyl is a stimulant laxative that does not take long to act and is therefore useful in acute constipation. The bulk-forming laxative ispaghula husk takes longer to act when compared with bisacodyl but is useful for long-term administration. Lactulose, which is an osmotic laxative, has a lag time of about 48 hours before onset of action. Loperamide and kaolin and morphine mixture are antidiarrhoeals used in acute diarrhoea. 

Polyethylene Glycol [PEG] 3350 (MiraLax) [Laxative] Uses Occasional constipation Action Osmotic laxative Dose 17 g powder (1 heaping tbsp) in 8 oz (1 cup) of H2O drink max 14 d Caution [C, ] R/0 bowel obst before use Contra GI obst, allergy to PEG Disp Powder for recons bottle cap... 

These agents may be used for the treatment of acute constipation or the prevention of chronic constipation. Magnesium oxide (milk of magnesia) is a commonly used osmotic laxative. It should not be used for prolonged periods in patients with renal insufficiency due to risk of hypermagnesemia. Sorbitol and lactulose are nonabsorbable sugars that can be used to prevent or... 

D. Constipation. For this syndrome osmotic laxatives seems efficient and erythromycin might be effective as well in some patients. 

Since food has a buffering effect, antacids are taken between meals (e.g., 1 and 3 h after meals and at bedtime). Nonabsorbable antacids are preferred. Because Mg(OH)2 produces a laxative effect (cause osmotic action, p. 170, release of cholecystokinin by Mg, or both) and Al(OH)3 produces constipation (cause astringent action of AP, p. 178), these two antacids are frequently used in combination. 

If drugs are used, the first choice should be a bulk laxative, e.g. isphagula or sterculia gum. Nonabsorbent carbohydrates with osmotic activity also work well but often cause flatulence. Salinic laxatives like polyethylene glycol and magnesium oxide are very effective but often cause stomach upsets like flatulence and abdominal pain. Tegaserod, a 5-HT4 partial agonist, appears to improve the frequency of bowel movements in those with chronic constipation (see Evans et ah, 2007). 

Lactulose (Constulose, Generlac, Enulose, Others) [Laxative/ Osmotic] Uses Hepatic encephalopathy constipation Action Acidifies the colon, allows ammonia to diffuse into colon Dose Acute hepatic encephalopathy. 30-45 mLPO qlh until soft stools, then tid-qid Chronic laxative therapy 30-45 mL... 

Antacid preparations based on aluminium hydroxide sometimes contain magnesium salts (and carbonate or oxide) to offset the constipating effect of the alumina. This laxative effect of salts such as magnesium sulphate (or citrate) and other saline cathartics such as potassium sodium tartrate is due to their incomplete absorption from the digestive tract so that, by osmotic forces, they retain water in the intestinal lumen. 

C Calcium and iron supplementation are common causes of constipation. Polycarbophil, a bulk-forming laxative, exerts its therapeutic effect by increasing the mass and water content of stool and by speeding transit time in the colon. Cascara sagrada and sennosides are cathartics, which speed colonic transit time and alter water and electrolyte transport across the colonic mucosa. Sodium biphosphonate is a saline cathartic, which increases intestinal peristalsis by osmotic properties. Docusate sodium is a stool... 

Glycerin is usually administered as a 3-g suppository and exerts its effect by osmotic action in the rectum. As with most agents given as suppositories, the onset of action is usually less than 30 minutes. Glycerin is considered a very safe laxative, although it may occasionally cause rectal irritation. Its use is acceptable on an intermittent basis for constipation, particularly in children. 

Lactulose is a hyperosmotic agent, which produces increased osmotic pressure within colon and acidifies its contents, resulting in increased stool water content and stool softening. It causes migration of ammonia from blood into colon, where it is converted to ammonium ion and expelled through laxative action. It is indicated in the treatment of constipation and prevention and treatment of portal-systemic encephalopathy, including stages of hepatic precoma and coma. 

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