Laxatives
Key Points
- Laxatives are classified by mechanism: bulk-forming (absorb water), osmotic (draw water into colon), stimulant (increase peristalsis), lubricant (coat stool), and stool softeners (emollients).
- Stimulant laxatives are first-line for opioid-induced constipation (OIC); stool softeners alone are insufficient for OIC.
- Adequate fluid intake (≥8 oz with bulk-forming agents) is essential to prevent bowel obstruction.
- Chronic stimulant laxative abuse causes electrolyte imbalances, dehydration, and bowel dysfunction.
- For polyethylene glycol (PEG 3350), standard OTC adult dosing is 17 g dissolved in 4-8 oz beverage once daily; prolonged unsupervised use should be avoided.
- Linaclotide is contraindicated in children younger than 2 years because severe dehydration and death have been reported in pediatric pathways.
Pathophysiology
Constipation results from reduced colonic motility, inadequate fluid intake, low dietary fiber, or drug-induced slowing of peristalsis (opioids, anticholinergics, antacids). Laxatives correct constipation through five distinct mechanisms:
- Bulk-forming: Increase stool bulk → stimulate peristalsis
- Osmotic: Draw water into colon → soften and increase stool volume
- Stimulant: Irritate colonic mucosa → increase peristalsis
- Lubricant: Coat stool and intestinal wall → facilitate passage
- Stool softener (emollient): Lower stool surface tension → allow water penetration
Classification
| Type | Examples | Onset |
|---|---|---|
| Bulk-forming | Psyllium (Metamucil), methylcellulose (Citrucel), calcium polycarbophil (FiberCon) | 12–72 hours |
| Osmotic | Lactulose, polyethylene glycol (MiraLAX), magnesium hydroxide (Milk of Magnesia) | 30 min–6 hours |
| Stimulant | Bisacodyl (Dulcolax), senna (Senokot) | 6–12 hours |
| Lubricant | Mineral oil | 8–48 hours |
| Stool softener (emollient) | Docusate sodium (Colace), docusate calcium | 12–72 hours |
| Miscellaneous | Linaclotide (Linzess), sorbitol | Varies by agent/route |
Nursing Assessment
NCLEX Focus
Patients on opioid analgesics should receive stimulant laxatives prophylactically — stool softeners alone do not counteract opioid-induced decreased peristalsis.
- Assess bowel elimination pattern, date of last bowel movement, stool consistency, and abdominal assessment before administration.
- Assess for signs of bowel obstruction or ileus (absent bowel sounds, severe pain, distension) — laxatives are contraindicated.
- Assess for appendicitis, perforation, or acute abdominal conditions — absolute contraindications.
- Assess current medications for opioids, anticholinergics, iron, calcium — common constipation causes.
- Assess fluid/food intake, activity level, and fiber consumption.
- Monitor for fecal-impaction pattern (severe bloating/cramping, small semiformed stool or watery leakage, rectal bleeding, vomiting, inability to pass flatus) and escalate before routine laxative dosing.
Nursing Interventions
- Administer bulk-forming laxatives with a full 8 oz glass of water to prevent esophageal or bowel obstruction.
- Administer bisacodyl tablets without crushing; do not give within 1 hour of antacids or dairy — enteric coating dissolves prematurely.
- Mineral oil should not be administered to bed-bound, children <6 years, or patients with dysphagia — aspiration risk causing lipid pneumonia.
- Avoid frequent long-term mineral oil use because absorption of fat-soluble vitamins (A, D, E, K) can decrease.
- Docusate (stool softener) alone is inadequate for opioid-induced constipation; combine with stimulant laxative (bisacodyl or senna).
- For PEG 3350, use measuring-cap 17 g dose dissolved in 4-8 oz liquid; typical OTC use is once daily and generally no longer than 7 days unless directed.
- For PEG 3350 in persistent constipation pathways, short supervised extension beyond OTC labeling (up to about 14 days) may be used per provider plan.
- For rectal bisacodyl, position left lateral with right knee flexed and instruct retention for about 15-20 minutes when possible.
- For bisacodyl enema, target retention around 10 minutes when tolerated before toileting.
- Verify product-specific pediatric labeling for mineral-oil enema use because minimum approved age varies by brand.
- Castor oil is contraindicated in pregnancy due to uterine-contraction risk.
Bowel Obstruction Risk
Bulk-forming laxatives without adequate fluid intake can cause esophageal or intestinal obstruction, especially in patients with strictures or limited mobility.
Stimulant Laxative Abuse
Chronic misuse of stimulant laxatives causes electrolyte imbalances (hypokalemia), dehydration, and cathartic colon (loss of bowel muscle tone). Monitor for abuse in eating disorder patients.
Linaclotide Pediatric Contraindication
Linaclotide is contraindicated in clients younger than 2 years due to severe dehydration risk.
Pharmacology
| Drug | Class | Key Nursing Considerations |
|---|---|---|
| Psyllium (Metamucil) | Bulk-forming | Drink 8 oz fluid; takes 12–72 hrs; safe for daily use; may lower cholesterol |
| Docusate (Colace) | Stool softener | Insufficient for OIC alone; onset 12–72 hrs; safe in pregnancy/postpartum |
| Bisacodyl (Dulcolax) | Stimulant | Available PO and rectal; do not crush tablets; avoid with antacids or dairy |
| Castor oil | Stimulant | Oral bowel-emptying option; avoid in pregnancy because of uterotonic risk |
| Senna (Senokot) | Stimulant/herbal | Often combined with docusate for OIC prophylaxis; overuse can cause diarrhea/dehydration/electrolyte loss; may discolor urine reddish-brown |
| Lactulose | Osmotic | Also lowers ammonia in hepatic encephalopathy; target 2–3 soft stools/day |
| Magnesium citrate | Saline osmotic | Often used for rapid bowel emptying and procedure prep; usually given with water and not for long-term repeated use |
| Polyethylene glycol (MiraLAX) | Osmotic | Standard adult OTC dose 17 g in 4-8 oz beverage once daily; may cause loose watery stool; avoid prolonged unsupervised use |
| Mineral oil enema | Lubricant | Usually works within minutes; monitor for anal irritation/dehydration/electrolyte issues and aspiration risk in vulnerable populations |
| Linaclotide (Linzess) | Miscellaneous (GC-C agonist) | Used in IBS-C/chronic idiopathic constipation; stop and notify provider if severe diarrhea occurs; avoid with suspected GI obstruction |
| Sorbitol enema | Miscellaneous osmotic | Rectal osmotic option for constipation episodes when ordered; monitor for cramping/diarrhea and hydration status |
Clinical Judgment Application
Clinical Scenario
A postoperative patient on IV morphine patient-controlled analgesia has not had a bowel movement in 3 days and reports abdominal bloating.
- Recognize Cues: Opioid-induced constipation (OIC) — reduced peristalsis; not responsive to docusate alone.
- Analyze Cues: Stimulant laxative + stool softener combination is the evidence-based approach for OIC.
- Prioritize Hypotheses: Constipation vs. paralytic ileus — bowel assessment needed first.
- Generate Solutions: Assess bowel sounds; administer bisacodyl + docusate per order if bowel sounds present.
- Take Action: Implement laxative regimen; encourage ambulation and fluid intake.
- Evaluate Outcomes: Patient passes stool within 24 hours; bowel routine established.
Related Concepts
- constipation - Clinical nursing management of constipation.
- opioids - Primary cause of opioid-induced constipation requiring prophylactic laxatives.
- antidiarrheals - Opposing class for managing loose stool.
- fluid-volume-deficit-hypovolemia-and-dehydration - Osmotic laxatives increase fluid loss risk.
- fecal-incontinence-and-bowel-retraining - Bowel regimen management context.
Self-Check
- Why is a stool softener alone insufficient for opioid-induced constipation?
- What is the critical patient education point when taking psyllium?
- What adverse effects result from chronic stimulant laxative abuse?