- Lubricant laxatives lubricate intestinal mucosa and soften stool.
- Caution: Administer on empty stomach at bedtime. Mineral oil prevents absorption of oil-soluble vitamins and drugs. With older patients, aspiration potential suggests that mineral oil should be avoided because it can cause lipid pneumonitis. It can interfere with postoperative healing of anorectal surgery. Avoid giving with docusate sodium. Docusate sodium causes increased systemic absorption of mineral oil.
- Use: Prophylactically to prevent straining in patients for whom straining would be dangerous.
- Drugs and dosages:
- Mineral oil: 5 to 30 cc at bedtime.
- Fecal softeners promote water retention in the fecal mass, thus softening the stool. Up to 3 days may pass before an effect is noted. Stool softeners and emollient laxatives are of limited use because of colonic resorption of water from the forming stool.
- Fecal softeners should not be used as the sole regimen but may be useful given in combination with stimulant laxatives.
- Caution: May increase the systemic absorption of mineral oil when administered together.
- Use: Prophylactically to prevent straining. Most beneficial when stool is hard.
- Drugs and dosages:
- Docusate sodium: 50 to 240 mg taken with a full glass of water.
- Docusate calcium: 240 mg each day until bowel movement is normal.
- Docusate potassium: 100 to 300 mg each day until bowel movement is normal; should increase daily fluid intake.
- Poloxamer 188: 188 mg (480 mg at bedtime).
Lactulose (Cholac, Cephulac)
- Lactulose is a synthetic disaccharide that passes to the colon undigested. When it is broken down in the colon, it produces lactic acid, formic acid, acetic acid, and carbon dioxide. These products increase the osmotic pressure, thus increasing the amount of water held in the stool, which softens the stool and increases the frequency of passage.
- Onset: 24 to 48 hours.
- Caution: Excessive amounts may cause diarrhea with electrolyte losses. Avoid giving to patients with acute abdomen, fecal impaction, or obstruction.
- Dosage: 15 to 30 cc each day (contains 10-20 g of lactulose).
Polyethylene glycol and electrolytes (Golytely, Colyte)
- Five packets are mixed with 1 gallon (3.785 L) of tap water and contain the following: polyethylene glycol (227.1 g), sodium chloride (5.53 g), potassium chloride (2.82 g), sodium bicarbonate (6.36 g), and sodium sulfate (anhydrous, 21.5 g). Do not add flavorings. Serve chilled to improve palatability. Can be stored up to 48 hours in the refrigerator.
- Use: To clear bowel with minimal water and sodium loss or gain.
Opioid antagonists (naloxone, methylnaltrexone)
Caution: Administer only if other drugs have failed.
- Subcutaneous methylnaltrexone, 0.15 mg per kilogram of body weight, can be administered daily or every other day to treat opioid-induced constipation. In a study of palliative care patients, including those with cancer and noncancer etiologies, approximately one-half of patients defecated within 4 hours of receiving the injection, with 30% of patients having a bowel movement within the first 30 minutes.
- In two studies of palliative care patients-one a single-dose trial and the other a 2-week every-other-day-dose trial-there was no evidence of withdrawal or other central effects of the opioid, and pain scores remained unchanged.[6,7]
- Caution: This drug is contraindicated in patients with bowel obstruction.
- The most common side effects are dizziness, nausea, abdominal pain, flatulence, and diarrhea.
- A study of prolonged-released naloxone in an oxycodone:naloxone ratio of 2:1 (average results of 40:20 mg, 60:30 mg, and 80:40 mg oxycodone:naloxone combination relative to placebo) demonstrated improved bowel function without reversal of analgesia.