Constipation in the general population is quite a common problem. It is even more common for women, older people, African Americans, and those with lower socioeconomic status. In addition, there are many medical conditions and drugs that can cause constipation. The focus here will be constipation caused by medications.
What is Constipation?
Constipation is not a disease, it is a symptom. It is poorly defined but constipation is generally considered to be a decrease in the frequency of bowel movements. Television, radio and now many internet sites will lead people to believe a daily bowel movement is required for a healthy digestive tract. In fact normal bowel movements can range between 3 per day to one every 3 days and still be considered normal. In an attempt to give constipation a better definition the Rome III criteria were developed. These guidelines generally describe increased straining, lumpy and hard stools, sensations of incomplete evacuations, blockage, the need for manual evacuation and three or fewer stools per week. See the above link for more details.
Drugs That May cause Constipation
There is are many medications which list constipation as a side effect. Some of the more common classes (with a couple of examples) include
- Narcotic pain medications: hydrocodone, oxycodone, codeine, morphine, methadone, meperidine, propoxyphene
- Some antacids: calcium carbonate, aluminum hydroxide
- Anticonvulsants: phenytoin, carbamazapine
- Antidepressants: amitriptyline, imipramine
- Blood pressure medications: clonidine, verapamil, diltiazem, nifedipine
- Some chemotherapy medications
- Iron supplements
- Parkinson’s medications
- Non-steroidal anti-inflammatory medications: ibuprofen, naproxen, diclofenac
Treatment of Drug Induced Constipation
There are many ways to treat constipation caused by medications. First you should talk to the doctor who prescribed the medication. A change in drug therapy may be in order if the problem persists or treatment of the constipation is not successful. Also, constipation in combination with nausea, vomiting or abdominal pain could indicate appendicitis and using a laxative could cause it to rupture.
Diet
Increasing fiber in the diet will help for most cases of drug induced constipation. The US Department of Agriculture recommends 14 grams of fiber per 1000 calories consumed. As a result a 2500 calorie diet requires 35 grams of fiber. The primary source of increased fiber should be from food such as grains, fruits and vegetables. Along with an increase in fiber comes an increase in fluids. If there are not enough fluids consumed, the fluid in the bowels are absorbed into the body resulting in hardening of the stool making it more difficult to pass. The standard recommendation for fluids is 6 to 8 eight ounce glasses of non-caffeinated beverages per day. .High fiber diet resources
Exercise
In general, people who walk less than 0.3 miles per day have more constipation while those who are physically active have less problems. Exercise, such as walking, helps the muscles in the intestines move the contents along reducing the chance of constipation. The benefit appears to be proportional to the amount of activity. As a result, moderate exercise should be introduced as tolerated.
Training
Keeping a set toilet routine can help lead to regular bowel patterns. After a meal the bowels undergo an increased in activity known as the gastro-colic reflex. This phenomenon is most pronounced after breakfast. Drinking a hot beverage may help to strengthen this reflex. Also when using the toilet, the knees should be higher than the hips (use a stool if needed), lean forward with elbows on knees, bulge the stomach out and keep the spine straight. This technique can make it easier to have a bowel movement.
Laxatives
Fiber and Bulk laxatives (psyllium, methylcellulose, bran) are usually considered to be safe and effective. They dissolve or swell in the intestines forming gels that promote bowel movements. When the constipation is due to medications, this class of drugs does not work well and may increase the risk of intestinal obstruction. As a result this class of laxative should be avoided for drug induced constipation.
Lubricant laxatives (mineral oil) coat the fecal materials with oil. This retains water in the stool and makes it more easily passed. Mineral oil must be taken while in an upright position and remain upright for 30 to 60 minutes after taking to prevent aspiration into lungs. Avoid use in people with hiatal hernia, difficulty swallowing, or reflux.
Osmotic laxatives (glycerin, magnesium hydroxide, sodium phosphate) draw water into the the bowels causing a loose or watery bowel movement. Some of these ingredients may be absorbed and cause electrolyte problems. Also, they may cause excessive fluid loss and dehydration. Check with your doctor if you have heart problems, kidney problems, or liver problems.
Emollients (softeners) (docusate sodium, docusate calcium) help water in the bowels to mix with the feces to help soften the stool. These should never be mixed with mineral oil. They are a good choice in combination with a stimulant.
Stimulant laxatives (senna, bisacodyl, castor oil) increase the activity of the bowels therefore pushing the contents along. They also help secretion of fluids into the bowels which is an added benefit. This is the preferred class of laxatives to treat drug induced constipation. It is especially useful in combination with one of the docusate products above.
In conclusion, there are numerous medications which may cause constipation. The most notable is the narcotic pain medications. If you are given pain medication, talk to your doctor from the start about using a laxative to prevent constipation.


