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Medications That May Cause Constipation as a Side Effect

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You may be surprised to find out that many things can cause constipation. Medications that may cause constipation as a side effect are more common than you think. Due to the national effort to increase awareness of the opioid epidemic, opioid-induced constipation has become a well-known fact.

Along with several other medications, your lifestyle and dietary preferences can cause or worsen constipation. Please continue reading to find out which commonly-used drug classes are associated with this unpleasant side effect. 

What is constipation?

Constipation is a widespread condition affecting 16% of adults in the US. Adults 60 years and older have an even higher risk-- approximately 33% of this population reports having symptoms of constipation. Many factors can contribute to the higher rate of constipation in older adults -- this is believed to be the combination of reduced gut motility, medication side effects, and a sedentary lifestyle. 

Constipation is defined as having three or fewer bowel movements per week. In addition to the frequency, the following symptoms can be indications of constipation:

  • Dry, hard stools, lumpy or “pebble-like” feces
  • Needing to push hard during a bowel movement
  • Difficult or painful bowel movements 
  • Having a feeling of incomplete emptying after a bowel movement 

The above symptoms are good indications of constipation; however, remember that defecation patterns can differ from person to person. If you have always had a bowel movement twice a week your entire life, this could be considered your normal, assuming there is no belly pain or bloating, you don’t have the sensation of incomplete emptying, and there is no pain or discomfort every time you go.

What causes infrequent bowel movements?

You might have been dealing with constipation for a long time or recently started experiencing infrequent stools with constant bloating and discomfort. So you try to figure out the cause of this condition to stop it; the answer is constipation has many causes. Besides lifestyle and certain health conditions, constipation can be a side effect of some medications. 

In some cases, people experience chronic idiopathic constipation (CIC); this bowel disorder causes chronic symptoms of constipation, but there are no clear causes. Generally, as mentioned above, constipation is a symptom of certain medical conditions or a side effect of some medicines. 

Medical conditions:

You might have heard of irritable bowel syndrome (IBS); people with IBS may have the subtype that causes diarrhea symptoms (IBS-D), and others might suffer constipation due to the IBS-C (irritable bowel syndrome with constipation) subtype. These two subtypes of IBS cause mixed symptoms. So IBS-C is an example where constipation is a symptom of this bowel disorder.

Health conditions affecting the nerves around the rectum and colon can also lead to constipation; examples of these neurological disorders include Parkinson’s disease, strokes, spinal cord injury, and multiple sclerosis (MS).

Keep in mind certain people have higher risks of developing constipation: pregnant women and older adults.


Lifestyle is one of the major causes of constipation.  


Both prescription and over-the-counter (OTC) medications can cause constipation. Many people are aware of opioid-induced constipation; however, several other drug classes cause constipation as a side effect.

Which OTC and prescription drugs can cause constipation?

Here are some of the medications that are commonly known to cause constipation:


Opioid pain medications, such as oxycodone (OxyContin, Percocet), tramadol (Ultram), and combination product like hydrocodone/acetaminophen (Vicodin), are associated with an increased risk of constipation--this is called opioid-induced constipation (OIC). Opioid pain medicines relieve pain by activating the opioid receptors in the body, including your digestive tract.

Activating these opioid receptors in the stomach leads to a few responses that contribute to constipation symptoms. First, the process of moving and emptying the stomach content is delayed causing the stools to remain in the intestines longer; as a result, more fluids get absorbed into the gut walls causing dry, hard stools. In addition,  the feeling of incomplete emptying with constant bloating also results from activating the opioid receptors in your digestive tract.

Opioid-induced constipation is an example of constipation due to the medication’s side effects. Keep in mind that this side effect can happen at any point of therapy, meaning constipation can occur soon after someone starts taking opioid medications, or it can happen gradually during opioid pain management.

If you take opioid pain medications, unfortunately, constipation is a very common side effect. Long-term treatment with opioids carries an even higher risk of opioid-induced constipation. The good news is that there are things you can do to help manage this risk and prevent chronic constipation. Most of the time, a laxative or a stool softener is prescribed for patients who are going to be on chronic opioid treatment. 

Laxatives are available over the counters and can be used as needed to relieve constipation. Senna and Dulcolax are first-line treatments for opioid-induced constipation. In addition to laxatives, lifestyle modification plays a major role in preventing chronic constipation. Drinking plenty of water, eating a high-fiber diet, and staying as active as possible are a few things you can do to prevent chronic constipation. Maintaining these lifestyle changes is also beneficial for your long-term health.     

Iron Supplements

Iron tablets (Slow Fe, Feosol, Femiron, Fergon, and others) can be hard on the digestive tract. They can cause side effects like constipation, bloating, gas, nausea, and indigestion. Iron in the form of ferrous bisglycinate (Niferex Gold Tablets) has been found to be less constipating, so it is worth exploring with your healthcare provider if you need iron supplements.

Tricyclic Antidepressants 

Tricyclic Antidepressants can cause constipation due to their anticholinergic effects. Anticholinergic drugs work by blocking the effects of acetylcholine, a natural compound of the central nervous system. By blocking acetylcholine, these medications affect certain parts of the brain that control nerve endings located in different body organs, such as the digestive tract in this case; for this reason, constipation and dry mouth happen.  

Tricyclic antidepressants (TCAs) are an older class of medications used to treat depression, anxiety, and insomnia (sleep problems). Examples of tricyclic antidepressants include amitriptyline (Elavil), desipramine (Norpramin), doxepin, and nortriptyline (Pamelor).

TCAs are generally used when other antidepressants have been shown to be ineffective. Using newer antidepressants such as selective serotonin reuptake inhibitors (SSRIs) and serotonin-norepinephrine reuptake inhibitors (SSNIs) can help improve constipation.


Antipsychotics are effective at treating schizophrenia and other psychotic disorders. Constipation is one of the most common side effects of antipsychotics, especially with clozapine (Clozaril, Versacloz, FazaClo ODT). How clozapine causes constipation is not clearly understood. Similar to tricyclic antidepressants, clozapine also affects other compounds in the central nervous system, such as dopamine and serotonin.  Interestingly, antipsychotics have varying degrees of anticholinergic effects. Therefore, choosing an agent with minor or less anticholinergic activity is an option if constipation is a major concern.

Calcium Channel Blockers

Constipation is a frequent side effect in patients taking blood pressure medications called calcium channel blockers. These medications, which are used to treat high blood pressure and other heart conditions, work by relaxing the heart muscles. However, they also relax the gut muscles, causing constipation. Examples include diltiazem (Cardizem), verapamil (Verelan, Calan SR), and others.


As mentioned earlier, drugs with anticholinergic effects can cause constipation. There is a wide variety of anticholinergics medications used to treat health conditions ranging from urinary incontinence to allergies. These medicines can cause constipation by blocking the movement of gut muscles. Examples include oxybutynin (Ditropan) and tolterodine (Detrol) for urinary incontinence and diphenhydramine (Benadryl), fexofenadine (Allegra), loratadine (Claritin), and cetirizine (Zyrtec) for allergies.

Nonsteroidal Anti-Inflammatory Drugs (NSAIDs)

Over-the-counter nonsteroidal anti-inflammatory drugs like ibuprofen (Advil, Motrin) and naproxen (Aleve) can cause constipation and stomach discomfort as adverse effects by slowing down activity in the digestive system. 

Acid Reflux Medications

Certain medications used to treat heartburn, such as antacids that contain aluminum or calcium (Maalox, Tums, Rolaids) and proton pump inhibitors (Tagamet, Pepcid, Axid), can cause constipation as an adverse effect. 

Oral Contraceptives

The hormones in oral contraceptives can affect gut motility and result in constipation. 

Overuse of Laxatives

Frequent use of stimulant laxatives or bulk-forming laxatives can make these medications less effective and lead to “rebound constipation,” which is very hard to treat. Overusing laxatives can make your body dependent on these drugs to pass stool and prevent you from having normal bowel movements. 

How to treat constipation caused by medication?

If your medication makes you constipated, the most important thing you can do is add fiber-rich foods to your diet, such as fresh fruits, vegetables, and whole grains. You should also stay well hydrated by increasing your fluid intake. Besides this, it’s important to get regular exercise. If these measures do not work, try taking a fiber supplement or stool softener—these are available over the counter at every pharmacy. 

Keep in mind that untreated constipation can lead to serious complications like fecal impaction, anal fissures, and anal prolapse in severe cases. If natural remedies and non-prescription medications for constipation do not work, talk to your doctor about switching from the medication that is causing constipation or taking prescription drugs to treat your constipation.



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