I was recently asked by a local practitioner to address issues of chronic constipation related to medications and to discuss treatment options for this problem.

Constipation is often a side effect of medications used to treat various ailments and chronic disease states.  For example medications used for treatment of high blood pressure can cause constipation. Constipation is a common problem in patients receiving narcotics for treatment of chronic pain, pain associated with injuries and surgery as well as those taking pain medications while undergoing treatment for cancer.

The effects of these medications on motility of the GI tract lead to the symptoms of constipation such as decreased stool frequency and difficult or painful evacuation of stool.  Early symptoms of constipation may simply be abdominal distention, pain and nausea. 

To understand how constipation occurs it is necessary to know the basics of colonic motility.  The body has a built in timing mechanism that tells the colon to have peristaltic contractions.  These organized coordinated contractions serve to move waste products (stool) out of the body.  The colon does not absorb significant amounts of nutrients and essentially no calories are absorbed in the colon.  The main function of the colon is to absorb water and to transport and rid the body of waste.  If the colonic motility is slow then more water is absorbed and therefore stools are hard and small.  If colonic motility is too fast then little water is absorbed and diarrhea is the result.  Certain medications alter the body’s natural rhythmic contractions and cause significant slowing of the movement of waste through the body.  Narcotics or “pain pills” are the biggest offenders. 

Sometimes simple remedies can give relief.  Increasing water consumption can help to keep the body well hydrated and help keep the stools soft.  Daily exercise has also been shown to help improve colonic activity.  Unfortunately these simple lifestyle changes may give little relief to the patient with chronic pain.  Exercise is often not an option for patients with recent surgery or severe injuries. 

Fiber supplements ( Psyllium and polycarbophil) absorb water and help to bulk the stools.  They have not been extremely effective in treating chronic constipation.  Bloating and gas are a major side effect and they must be taken with at least 8 ounces of water.  They may decrease absorption of certain medications.


Pharmacological therapy is often needed for symptom relief.  Options for over the counter treatment include osmotic agents, stimulant laxatives and stool softeners.

Osmotic agents are large molecules that are not absorbed into the body but reach the colon and serve to draw fluid into the lumen thus making the stools softer. Polyethelene glycol or Miralax is available over the counter.  Lactulose, a large sugar molecule, is available by prescription.  These are safe and can be used daily.

Stimulant laxatives such as biscodyl (Exlax, Correctol, Dulcalax) increase muscle contractions.  Side effects include cramping, excessive fluid loss, dehydration and electrolyte disturbances.  Chronic long term use of stimulant laxatives can lead to loss of colon function.  Nerves in the colon can be damaged causing the colon muscles to weaken making constipation worse.

Saline laxatives (Magnesium citrate) use ions to draw fluid into the intestine.  These should not be used in patients with congestive heart failure or kidney disease.  The oral phosphasoda preparations have been removed from the market due to problems associated with kidney disease with use of these.

Lubricants such as mineral oil, coat the bowel and stool with a waterproof film keeping moisture in the stool.  Castor oil works in the small bowel promotes evacuation and works within 2-6 hours.  This can effect absorption of nutrients and minerals form the intestine and should not be used every day.

Stool softeners (Colace or docusate) help liquids mix into the stools.  As the name implies the stools will become more soft but will not improve stool frequency.

Starting a bowel regimen early in the treatment can help to avoid severe constipation.  If you are taking narcotics on a daily basis for short term management of pain or chronically for pain control you should discuss these treatment regimens with your physician.  Often a combination of stool softeners and laxatives are needed for symptom relief and to maintain a healthy colon.
If you are pregnant you should consult your physician before taking any over the counter regimens for constipation.  If with these simple options constipation continues to be a problem there are other prescription medications that may be used.  Further evaluation by a specialist such as a gastroenterologist may be indicated.