Medications are a major reason for constipation. Pain medications are the biggest culprit with opioids (Vicodin, Norco, Tylenol with codeine, etc) and nonsteroidal anti-inflammatory drugs (NSAIDS) leading the pack. Constipation can become a bigger struggle for you than the illness that led you to take the medications causing it, and will make any post-operative course miserable. So, why does this happen and what works for the treatment of medication-induced constipation?
Why does this happen?
Opioids and other medications affect parts of the stomach and intestine (particularly the colon), altering nerve input to the gastrointestinal tract which inhibits movement. Opioids also increase the absorption of electrolytes and water (making drier and thus harder poops), increase anal sphincter tone, and reduce sensitivity to the presence of stool. These factors lead to constipation, hard stools, and misery.
What really works?
- Stimulant Laxatives: Senna (sennosides, Ex-Lax) and bisacodyl (Dulcolax) increase intestinal motility and help with the flow of water INTO the bowel which improves constipation. SENNA is more commonly used and slightly more effective than bisacodyl for opioid-induced constipation. Both are available over the counter and cheap.
- Osmotic Laxatives: These include magnesium or phosphate-containing laxatives, non-absorbable sugars (lactulose, sorbitol, glycerin), and polyethylene glycol (Miralax). Osmotic laxatives work by increasing fluid accumulation in the colon and small intestine, which improves constipation. These are all effective for treatment of opioid-induced constipation but some evidence shows that lactulose is better than sorbitol, and Miralax is better than lactulose. Hmmm, so is Miralax the best?
- Emollient Laxatives: These include Colace (docusate), or mineral oil. Know that emollient laxatives are inferior to the osmotic and stimulant laxatives for the treatment of drug-induced constipation. So, this should be your third choice.
- The newest: Methylnaltrexone (Relistor) is an injection and the newest medication for opioid-induced constipation. Relistor is expensive, but has been found to provide good relief of constipation in terminally ill patients who do not respond to laxatives. Relistor is your last choice if all else has failed.
What doesn’t work?
Fiber and bulk laxatives (psyllium, metamucil, bran, fibercon, Citrucel, etc.) are generally not effective for the treatment of drug-induced constipation. Don’t go there.
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