Drug’s for constipation
Reading File
Finding Sources
Finding Sources
Searching PubMed
"constipation"[MeSH Terms] AND "laxatives"[MeSH Terms]
Reading File
Reading File
Reading File
Reading File
Reading File
Reading File
I now have comprehensive content from both Lippincott and Goodman & Gilman. I also have enough for newer drugs (lubiprostone, linaclotide, plecanatide from G&G). Let me compile a thorough response.
Drugs for Constipation
Laxatives are the primary pharmacological tools for constipation. They work by three broad mechanisms: retaining intraluminal fluid (osmotic/hydrophilic), decreasing net fluid absorption, or altering motility (stimulating propulsive contractions or inhibiting segmenting contractions). Current guidelines recommend osmotic or stimulant laxatives as first-line strategies; dietary fiber (20-35 g/day) and adequate fluid intake should always be tried first.
- Lippincott Illustrated Reviews: Pharmacology, p. 1438; Goodman & Gilman's, p. 1110
1. Irritants / Stimulant Laxatives
These act directly on intestinal mucosa to stimulate propulsive contractions and increase fluid/electrolyte secretion into the bowel.
| Drug | Brand | Notes |
|---|---|---|
| Senna | Ex-Lax, Senokot | Anthraquinone glycosides; oral onset 6-12 h; useful for opioid-induced constipation (combined with docusate) |
| Bisacodyl | Dulcolax, Correctol | Diphenylmethane; available as oral tablets or suppositories; acts on mucosal nerve fibers; potent colonic stimulant |
| Castor oil | Generic | Converted to ricinoleic acid in small intestine; irritates GI tract strongly; NOT recommended routinely due to poor palatability and GI side effects; contraindicated in pregnancy (can trigger uterine contractions) |
| Sodium picosulfate | - | Diphenylmethane class (G&G); similar to bisacodyl |
| Cascara | - | Anthraquinone class; similar to senna |
Use stimulant laxatives at the lowest effective dose for the shortest period to avoid dependency and chronic diarrhea.
2. Bulk-Forming Laxatives
Hydrophilic colloids from indigestible plant matter. They absorb water in the intestine, swell to form gels, cause distension, and stimulate peristalsis. Onset: 1-3 days (slowest).
| Drug | Brand |
|---|---|
| Psyllium | Metamucil |
| Methylcellulose | Citrucel |
| Bran | - |
| Calcium polycarbophil | - |
Cautions: Use with caution in immobile patients (risk of obstruction). Psyllium can reduce absorption of other oral medications - separate administration by at least 2 hours.
3. Saline and Osmotic Laxatives
Nonabsorbable ions or sugars draw water into the intestinal lumen by osmosis, distend the bowel, and accelerate evacuation. Onset: 1-3 hours (fastest conventional laxatives at cathartic doses).
| Drug | Brand | Notes |
|---|---|---|
| Polyethylene glycol (PEG) | MiraLax, GoLytely | Osmotic; electrolyte-free powder causes less cramping/gas; high-volume PEG solutions used for colonoscopy prep |
| Lactulose | Constulose, Enulose | Semisynthetic disaccharide; not hydrolyzed by GI enzymes; colonic bacteria ferment it to organic acids increasing osmotic pressure; also used for hepatic encephalopathy (reduces ammonia) |
| Magnesium citrate | Citroma | Saline cathartic; rapid acting |
| Magnesium hydroxide | Milk of Magnesia | Saline cathartic |
4. Stool Softeners (Emollient Laxatives / Surfactants)
Surface-active agents that emulsify with stool, allowing water to penetrate. They soften stool but do not stimulate motility. Used for prophylaxis rather than acute treatment. Onset: 1-3 days.
| Drug | Brand |
|---|---|
| Docusate sodium | Colace |
| Docusate calcium | Surfak |
Caution: Do NOT take with mineral oil (risk of mineral oil systemic absorption).
5. Lubricant Laxatives
Coat/lubricate stool surface to ease passage of hard stools.
| Drug | Notes |
|---|---|
| Mineral oil | Oral; must be taken upright to avoid aspiration and lipoid pneumonia |
| Glycerin suppositories | Rectal; provides lubrication and mild osmotic effect |
6. Chloride Channel Activators (Prosecretory Agents)
Newer agents that work by stimulating intestinal fluid secretion.
| Drug | Mechanism | Use |
|---|---|---|
| Lubiprostone | Activates ClC-2 chloride channels in intestinal epithelium - increases luminal fluid secretion | Chronic idiopathic constipation, IBS-C; minimal drug interactions; no tolerance/dependency |
| Linaclotide | Guanylate cyclase-C (GC-C) activator - increases cGMP - stimulates CFTR chloride channel and intestinal secretion | Chronic constipation, IBS-C |
| Plecanatide | GC-C activator (pH-sensitive) | Chronic constipation |
| Tenapanor | NHE3 (sodium-hydrogen exchanger 3) inhibitor - reduces sodium absorption causing fluid secretion into lumen | IBS-C |
7. Prokinetic Agents
Primarily act on gut motility rather than fluid secretion.
| Drug/Class | Mechanism |
|---|---|
| 5-HT4 receptor agonists (e.g., prucalopride) | Stimulate propulsive contractions in colon |
| Dopamine receptor antagonists | Metoclopramide (mainly upper GI) |
| Motilides (erythromycin) | Motilin receptor agonist; accelerates gastric emptying |
8. Drugs for Opioid-Induced Constipation (OIC)
A special category - peripherally acting mu-opioid receptor antagonists (PAMORAs) that block opioid receptors in the gut without reversing analgesia:
| Drug | Notes |
|---|---|
| Methylnaltrexone (Relistor) | Subcutaneous injection |
| Naloxegol (Movantik) | Oral |
| Naldemedine (Symproic) | Oral |
Summary Table: Onset of Action
| Laxative Class | Onset |
|---|---|
| Stimulants (oral) | 6-12 hours |
| Osmotic/Saline (cathartic dose) | 1-3 hours |
| Osmotic (laxative dose, e.g. PEG) | 1-2 days |
| Bulk-forming | 1-3 days |
| Stool softeners | 1-3 days |
| Suppositories/enemas | 15-60 min |
Key Clinical Points
- First line: Osmotic laxatives (PEG, lactulose) or stimulant laxatives (senna, bisacodyl)
- Stimulant laxatives are recommended when osmotic agents fail
- Chronic laxative use risks electrolyte imbalance (hypokalemia), secondary hyperaldosteronism, protein-losing enteropathy, and dependency
- Newer prescription agents (lubiprostone, linaclotide, prucalopride) are reserved for chronic constipation unresponsive to standard laxatives
- Many drugs cause constipation (opioids, anticholinergics, calcium-channel blockers, iron, antacids with aluminum/calcium) - stopping or reducing these is an important step
Sources: Lippincott Illustrated Reviews: Pharmacology, pp. 1438-1440; Goodman & Gilman's Pharmacological Basis of Therapeutics, pp. 1108-1112
This is a shared conversation. Sign in to Orris to start your own chat.