Understanding Why Opiates Make You Nauseous

Opiates are a class of drugs that include prescription painkillers, as well as illegal drugs like heroin. Prescription opiates are intended to be used by people who have moderate to severe levels of pain, often following surgery or an injury. While opiates do have therapeutic benefits regarding helping people manage serious or chronic pain, they also have many potential risks.

There are hundreds of millions of prescriptions written each year for opiates, which are highly addictive drugs. Because the brain develops a tolerance to opiates quickly, people are more likely to become physically dependent on opiates. This physical dependence leads to use of higher doses, or more potent opiates, to achieve the same effects.

Unfortunately, even proper use of a prescription opioid can lead to addiction and use of stronger opiates such as heroin.

Regardless of whether you’re using opiates to control pain, as prescribed by your doctor, or you’re abusing opioids, there is the potential for a lot of adverse side effects, in addition to the possibility of abuse.

How Opiates Work

Before exploring the specific reasons why opiates can cause nausea and even vomiting, it’s useful to have an overview of how these drugs work and the areas of the brain and body that are impacted by their use.

Opiates bind to opioid receptors located throughout the brain and spinal cord. They reduce messages and feelings of pain, but they can also flood the brain with dopamine, which is what causes the rush of pleasure, or euphoria, associated with opiate use.

Some common side effects of opiate use include nausea, drowsiness, and constipation. Regular use of opiates, whether for medicinal or recreational purposes, can lead to a tolerance very easily. Continued use over time can progress to opiate dependence. When one is dependent on opiates, he or she will most likely experience withdrawal symptoms when opiate use is stopped. Opiate withdrawal symptoms include nausea, vomiting, pain, anxiety and emotional disturbances, among other symptoms.

Why Opiates Make You Nauseous

Opioid-induced nausea, and sometimes vomiting, occurs because of something in the brain called the chemoreceptor trigger zone (CTZ).

The CTZ is a ventricle in the brain that is triggered when it detects substances not meant to be in the blood. It’s located in the medulla oblongata, and it works by receiving input from drugs or hormones, which trigger areas of the brain to induce vomiting. Certain neurotransmitters triggered by opiates can cause one to feel nauseated and can also induce vomiting.

Another reason why opiates cause nausea is their effect on vestibular function. This can lead to a feeling that the room is spinning, which can cause nausea.

With that being said, there are some specific things to note about why opiates make you nauseous, and why people might experience this symptom differently.

First, not all opiates necessarily create the same level of nausea. There has been some evidence indicating morphine and codeine tend to lead to the most nausea, but this could also be because they’re among the most frequently prescribed opiates.

Some people are more susceptible to this effect from opiates. An increased likelihood of nausea may be due to genetic factors.

Also, most people rapidly develop a tolerance to the effects of opiates, so within a period of days the nausea of subsides after people initially start using these drugs.

Opiate Withdrawal

Another specific scenario where opiates cause nausea is during withdrawal. If someone has been regularly using opiates and they attempt to stop using them, particularly if they go cold turkey and stop suddenly, they will very likely experience nausea and vomiting.

Many of the body’s systems are so heavily impacted by the use of opiates that when a person stops using them suddenly, those systems go into overdrive trying to stabilize and compensate for the lack of the presence of the drug.

To sum up, why opiates make you nauseous, it’s a bit of a complicated process that involves certain areas of the brain and opioid receptors that are activated when these drugs are taken, as well as an action of the brain that tends to create the feeling of spinning. While the reasons why opiates cause nausea may subside after a few days of taking them, nausea often returns when someone is in withdrawal from these drugs as well.

Editor – Megan Hull

Megan Hull is a content specialist who edits, writes and ideates content to help people find recovery. Read more

Medically Reviewed By – Patrick Moser, MSN, FNP

Patrick is a nationally-certified Family Nurse Practitioner who primarily works with adult patients with mental health conditions or problems with addiction. Read more