Why Opiates Cause Constipation

Constipation isn’t just a side effect of opiates. Several other types of medicines that are used to treat pain and illnesses can also cause constipation. However, opiate-induced constipation is often more common than constipation associated with other medications.

Also relevant to answering the question “Why opiates cause constipation?” is the fact that unlike many of the other side effects of opiates, like nausea, constipation doesn’t go away over time with continued use of the medicine or drug. One of the reasons this is believed to be the case is because the gastrointestinal system doesn’t seem to be able to get used to the presence of opioids the way other parts of the body do.

As a result, the longer a person takes opiates, the more likely they are to become constipated from opioids.

So, what are the specific reasons why opiates cause constipation?

The gastrointestinal (GI) tract is often called the second brain because of its complicated neural network. The neurons found in the GI can be heavily impacted by the use of opioids. Muscles that surround the intestines are responsible for pushing stool through the body. When a person takes opioids, the squeezing movements of these muscles slow or even stop altogether because of the way opioids impact the messages sent to the nerves in the intestines and spine. The messages tend to get confused to the extent that both ends of the stools are being squeezed, causing the stool to become trapped in the intestines.

Taking opioids can also paralyze the stomach partially, leading to a condition called gastroparesis. When this happens, food lingers in the digestive tract for longer than usual. When the action of the gut slows, the intestines can absorb too much water, causing hard, dry stools to form.

What differentiates opiate-related constipation from other forms of constipation is the fact that opiate-related constipation affects opioid receptors throughout the body, as well as the functionality of the brain. Because of this, taking fiber or other supplements often can’t remedy the problem.

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