Constipation and Pain Killers

Aug 20, 2019

By: Trevor Shewfelt, Pharmacist at the Dauphin Clinic Pharmacy

Lots of lingerie but no books. I was in Polo Park the other weekend. I was killing time while waiting to pick up my sister at the airport. Eric needed to buy more shorts. He is growing like a weed. He also needed sandals. But I'm not allowed to call them sandals. They are called slides. I hadn't been to Polo Park in a few years and my kids were acting like they've never been to a mall. It was so big and confusing they said. Let's go back to that food court place. I was making fun of them for being hayseeds, but maybe, like usual, I'm just being old.

Another joy of getting older is pain. From injuries to arthritis to post-surgical pain all pain seems to happen more as we age. A common side type of pain killer are opioids. An unexpected side effect of opioids is constipation. Opioids and narcotics are different names for the same thing. These medications originally came from the opium poppy. The most common of these is morphine, but opioids also include codeine, meperidine, oxycodone, hydromorphone, and several others. These medications do a very good job of suppressing pain, but they commonly cause constipation.

For opioids like morphine to kill pain, they attach to an opioid receptor in the brain. For opioids like morphine to cause constipation, they attach to a receptor outside the brain. That is how the diarrhea prevention drug loperamide or Imodium works. It binds to the same mu-opioid receptor morphine does, but it isn't able to cross the blood brain barrier. That means it just causes constipation, but doesn't do any pain killing.

Do we have to worry about constipation in everyone on every opioid? Probably not. If someone is on Tylenol #3 (which contains codeine) as needed for a sprained ankle, we probably don't need to worry about constipation. They will probably only need their opioid for 3-4 days. However, if someone is on a regular opioid for a week or longer, we should start talking about constipation prevention.

Prevention of opioid induced constipation should begin by using non-drug measures. These measures include eating more fiber. Choose fruits such as apples and oranges, vegetables such as peas and broccoli, and whole grains such as oats and brown rice to get more fiber. You can also eat foods such as cereal bars with added fiber, or fiber supplements like Metamucil. A person should also drink 6-8 glasses of water per day because the water helps the fiber do its job. Regular exercise like walking will also help with constipation.

Unfortunately, eating more fiber, drinking water and exercise might not help prevent opioid induced constipation. For opioids we reach for laxatives. The most gentle of these are the osmotic laxatives. Osmotic laxatives like PEG 3350 have brand names like Laxaday and Restoralax. They work by drawing more water into the gut. They are usually well tolerated and not that expensive. They don`t cause as much cramping as stimulant laxatives and are considered safe for long term use if a patient needs to be on an opioid pain killer for an extended period of time.

The next step up in strength is the stimulant laxatives like bisacodyl. When I was in pharmacy school, we were taught they weren`t safe for long term use. We were told they would lead to lazy bowels that wouldn`t work without laxatives if they were used long term. Lately, it has been found there is limited proof that long term stimulant laxative use will cause lazy bowels and they are considered safe in long term treatment of opioid induced constipation.

Another change has been the use of stool softeners like docusate calcium and docusate sodium. Stool softeners don't seem to be particularly useful for either treating or preventing constipation. Stool softeners aren`t what we should be reaching for when someone has opioid induced constipation.

For long term opioid pain treatment, we should offer laxative to prevent or treat constipation as an annoying side effect.

Even though I grew up in a much smaller town than Dauphin, it seems like we were in a mall every other weekend. That's where we shopped, went to the movies and had Orange Julius. My kids shop on Amazon, watch movies from Netflix on their phones and can get an Orange Julius at Dairy Queen. Maybe malls will soon be gigantic relics from a past age. Or at least what is sold in malls may change dramatically. I couldn't find a single bookstore in Polo Park. I've always loved browsing through physical bookstores. But I counted at least five lingerie shops. I'm not sure what that says about shopping in the future. But, I guess the future will be .... silky?

As always if you have any questions or concerns about these or other products, ask your pharmacist.

The information in this article is intended as a helpful guide only. It is not intended to be used as a substitute for professional advice. If you have any questions about your medications and what is right for you see your doctor, pharmacist or other health care professional.


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