Five different mechanisms, one shared goal: relieve constipation. This is the mirror image of the Anti-diarrheal page — instead of slowing motility and drying secretions, laxatives pull water in, irritate the bowel wall, or add bulk to speed things up. Pick the class by how fast you need it to work.
Dehydrates local tissue → irritation, ↑ peristalsis
Lactulose (oral) / Glycerin (rectal)
Oral 24–48 hr; rectal 15–60 min
Saline
Pulls water into intestine osmotically → ↑ pressure, ↑ peristalsis
Magnesium hydroxide (MOM)
30 min – 6 hr
Stimulant / irritant
Direct action on intestinal wall → ↑ peristalsis
Bisacodyl, Senna, Cascara sagrada
Oral 6–12 hr; rectal 15–60 min
Stool softener
Promotes water retention in the fecal mass — softens without stimulating
Docusate (Colace)
12–72 hr
Lubricant / emollient
Coats stool & intestinal wall; does not add water to stool
Mineral oil
6–8 hr
🧠 "BOSS-L" — Bulk, Osmotic/saline, Stimulant, Softener, Lubricant. Onset roughly matches how aggressive the mechanism is: gentle bulk-forming is slowest, saline/stimulant rectal routes are fastest.
✅ Indications by class
Stimulant, emollient, saline — evacuate the colon before rectal/bowel exams or surgery
Psyllium / polycarbophil — IBS and diverticular disease
Hyperosmotic (lactulose) — reduces blood ammonia in hepatic encephalopathy
🧠 "Don't strain that heart or that stoma." Stool softeners are the classic answer for the post-MI or post-rectal-surgery patient.
🔗 Mirror image: Laxatives vs. Anti-diarrheal
🚽 Laxatives
🚫💧 Antidiarrheals
Pull water INTO the gut
Promote water reabsorption
↑ peristalsis
↓ peristalsis
Treats constipation
Treats diarrhea
🧠 Same gut, opposite dial. If you can explain one page, you can explain the other by just flipping every arrow.
⚠️
WATCH FOR
STEP 2 · KNOW THE RISKS
"Natural" and "OTC" doesn't mean risk-free — electrolytes, obstruction, and dependence are all real.
🚨 Adverse reactions & the obstruction trap
Constipation (paradoxically), diarrhea with water/electrolyte loss, abdominal pain or discomfort, nausea, vomiting, perianal irritation, fainting, bloating, flatulence, cramps, and weakness. Prolonged use can cause serious electrolyte imbalances and the "laxative habit" — dependence on a laxative to have a bowel movement.
🧠 "Bulk without water is a brick, not a broom." Always pair bulk-forming laxatives with a full glass of water or more.
❌ Contraindications
Known hypersensitivity
Persistent abdominal pain
Nausea or vomiting of unknown cause
Signs of acute appendicitis
🧠 "Don't clear an appendix that's about to burst." Never give a laxative for an undiagnosed acute abdomen — it can worsen a surgical emergency.
🔀 Interactions
Mineral oil impairs absorption of fat-soluble vitamins A, D, E, K
Laxatives may reduce absorption of other drugs present in the GI tract
Surfactants (like docusate) given with mineral oil can increase mineral oil absorption
Milk, antacids, H2 antagonists, and PPIs should not be given 1–2 hours before bisacodyl tablets — the enteric coating can dissolve early, causing gastric irritation/dyspepsia and a weaker laxative effect
🧠 "ADEK gets locked out" with chronic mineral oil use — the fat-soluble vitamins ride out with the oil instead of being absorbed.
⚠️ Caution & harmless side notes
Magnesium products — use cautiously in any degree of renal impairment (risk of accumulation)
Tartrazine (yellow dye) in some products may cause allergic reactions, including bronchial asthma, in susceptible patients
Cascara sagrada or senna can cause pink-red, red-violet, red-brown, yellow-brown, or black urine — expected, harmless discoloration
🧠 Weird urine color after senna? Expected, not an emergency. Reassure, don't panic.
🎓
TEACH
STEP 3 · PREVENT DEPENDENCE
The best long-term laxative is fiber, fluid, and movement — drugs are the backup plan.
✅ Nursing management ladder
1
⛔ Avoid long-term use unless recommended by the HCP — risk of "laxative habit" / dependence
2
⚖️ Not for weight loss — read and follow label directions
3
🚫 Do not use with abdominal pain, nausea, or vomiting present
4
📞 Notify the HCP if constipation isn't relieved, or if rectal bleeding/other symptoms occur
5
💧 Prevent the need: plenty of fluids, exercise, high-fiber/roughage diet — the real long-term fix
🧠 "Fiber, fluid, feet." The three F's prevent constipation without a single pill.
🧪 Bulk-forming laxative safety
Take with a full glass of water or more, every time. Without enough fluid, the swelling mass can obstruct the esophagus, stomach, small intestine, or colon — especially in a patient with known intestinal stenosis.
🚨 Neverwith abdominal pain, N/V, or suspected appendicitis
💧 Fluid = safetyespecially with bulk-forming agents
⚠️ Short-term onlylong-term use → dependence + electrolyte loss
🎯 Cover & check — 4 rapid-fire questions
Q1: Name one key clue that tells bulk-forming apart from stimulant laxatives.
Bulk-forming absorbs water and adds mechanical bulk (onset 12–72 hr); stimulant laxatives directly irritate the intestinal wall to trigger peristalsis (onset 6–12 hr oral, much faster rectally).
Q2: Name one priority — when should a laxative be withheld?
Persistent abdominal pain, nausea/vomiting of unknown cause, or signs of acute appendicitis — never mask a possible surgical abdomen.
Q3: Name one teaching point about bulk-forming laxatives.
Take with a full glass of water every time — without enough fluid it can obstruct the esophagus, stomach, small intestine, or colon.
Q4: How does the laxative mechanism mirror the anti-diarrheal page?
Laxatives pull water into the gut and increase peristalsis; antidiarrheals promote water reabsorption and decrease peristalsis — same organ, opposite direction.