Opioid Side Effects: How Do Opioids Affect The Body And Brain?

Last Updated: May 5, 2020

Reviewed by Michael Espelin APRN

Opioids are substances that help with pain management by producing pain-relieving and euphoric effects. These include both prescription painkillers as well as some illicit substances. Although they provide temporary relief to the user, opioid side effects can affect a patient’s well-being. Side effects of opioids that can be risky in both short term and long term. Find out how do opioids affect the body, can they be taken during pregnancy, and how to manage adverse effects of opioids?

What Are The Common Side Effects Of Opioids?

Taking opioid medication on a regular basis can have the following side effects:


This is the most common side effect of opioids. Taking them on a regular basis can lead to a change in bowel movements, and thus the user may suffer from stomach issues, such as constipation, for the time period in which they were. Opioid-induced constipation treatment should be sought if this side effect appears in the patient.


Side effects of opioids often appears as stomach discomfort and the sensation to vomit, commonly called nausea. According to research, after constipation, this is the most common side-effect observed. This may also lead to a lack of appetite and deteriorating health, consequently.

 nausea from opioids


Another common side effect of opioids is dizziness. The euphoric effect of the substance is likely to make the user feel tired and sleepy. As a result, the user may sleep for long periods (until the effect of the pill wears off). Extreme dizziness is known among the signs of an opioid overdose. This condition can be deadly and requires immediate professional help.

Opioid-induced Hyperalgesia

This is perhaps the riskiest side effect of opioids. Opioid-induced hyperalgesia refers to a condition where taking a high dose results in a lowering of pain threshold. As a result, the pain worsens and becomes unmanageable even with accelerating the doses. The user may also experience unusual pain symptoms such as allodynia. If the current medication isn’t working anymore, a patient should ask a doctor to use opioid conversion for switching the medicine.

Dry Mouth

Frequent use may also lead to less production of saliva in salivary glands. As a result, the user may have a dry and parched sensation in the mouth. In medical terms, this condition is called xerostomia.

Itching and Other Allergies

Another common opioid side effects are allergies. In some cases, it results in an allergic reaction such as opioid itching, which can cause discomfort. The user must consult the doctor about this side effect, even if a mild symptom is observed.


This is another one of the most common opioid side effects. It might sound ironic that a substance used to relieve pain causes a headache – but it’s true. Headaches caused by this medication are known as rebound headaches.

suffering from opioids headache
These are some common side effects of opioids experienced in the short-term. However, long-term use can pose a severe threat to the health of the user.

Long Term Side Effects Of Opioids

When opioid or opiate is taken for a long time period, they can have some serious side effects on the user’s health, such as:

Erectile Dysfunction

One of the side effects of opioids on prolonged use is erectile dysfunction. The research found out that men who were using them were about 50% more likely to experience sexual dysfunction as a side effect as compared to those who do not use this medication. Opioid substances do not only interfere with the production of testosterone but also lessen interest, excitement, and sensation – resulting in erectile dysfunction in men.

Cardiac Problems

Although no direct link between opioid usage and heart failure has been established, there are many severe cardiac problems linked to the long-term side effects of opioids, including impaired functioning of the heart muscle, slower heart rate and dilation of blood vessels. Apart from these, ventricular tachycardia, a type of cardiac arrhythmia, atrial fibrillation, and infectious endocarditis are also fairly common heart side effects associated with prolonged use.

Kidney Damage

Long-term side effects of opioids can result in chronic kidney damage. This is because it leads to a decrease in fluid intake, which can result in severe dehydration (if not noticed early). Furthermore, by causing multiple interruptions in the micturition reflex, opioid side effects can result in urinary retention, where a significant amount of residual urine is left behind due to impaired emptying of the bladder. Both of these factors lead to kidney damage.

 renal replacement therapy

Respiratory Depression

How do opioids cause respiratory depression? According to research, prolonged use of this medication can alter the functioning of specific components of the user’s central nervous system, including the pre-Bötzinger complex, a respiratory rhythm generating area in the pons. This is called opioid respiratory depression.
Use of drugs that activate the mu-opioid receptor cause analgesia linked to respiratory depression. Different medicine contains different amounts of opioids. Thus, their effect on the respiratory system varies.


Since they produce pleasurable and euphoric effects, they are highly addictive and thus, long term use of this substance – especially in the form of drugs – can lead to abuse and addiction. This is a grave issue, which can cause severe physical and mental problems.
If some signs of abuse are noticed in a patient, they should immediately seek addiction treatment for opioids. This condition brings severe risks because the user becomes highly dependent on the drug and loses control of the senses and body when withdrawal occurs. Addiction can end up lethal. According to opioid crisis statistics, around 72000 people died in the US in 2017 due to opioid addiction.

Opioids And Pregnancy: Taking Opioids While Pregnant

During pregnancy, a woman’s body undergoes massive hormonal changes, and it is likely to react to medication differently than under normal circumstances. Thus, it can be said that pregnant and breastfeeding women are at a higher risk of suffering from the dangerous side effects of opioids.
The use of painkillers, such as oxycodone, hydrocodone, codeine, hydromorphone, and fentanyl, must be strictly avoided during pregnancy. These pills should be considered as a last resort. This is because not only do these pills have adverse side effects, and they are also highly addictive and prolonged use of opioids in pregnancy can lead to addiction. Pregnant women with this disorder are at an increased risk of serious complications, including placental abruption, abnormal fetal growth, premature birth, and stillbirth in extreme cases.

Dangers Of Having Neonatal Abstinence Syndrome In Baby

This is called Neonatal Abstinence Syndrome (NAS). Some of the symptoms of NAS commonly observed in infants are:

  • Shaking and tremors
  • Irritability
  • fever
  • diarrhea
  • poor sleeping patterns
  • difficulties in feeding.

NAS usually lasts for days or weeks, depending upon how severe it is. Swaddling, breastfeeding, skin-to-skin contact, and sometimes medications can help babies with NAS feel better. Although NAS can be hard to deal with, there are no known lasting physical or mental effects of it on babies.

Pregnant young woman visiting doctor
Regular usage of these meds is not safe for infants on breastfeeding as well. Generally, if the amount of a sedative drug excreted in breast milk is less than 10%, it is considered safe for the infant. It depends on opioids half-life and patients features. However, in the case of codeine and oxycodone, the infant is at risk of sedation even if the amount is less than 10%. As a result, prolonged use of opiates can adversely affect the infant’s central nervous system (CNS). Mothers who use these drugs must keep an eye on their breastfed infants for signs of CNS depression.

Managing Opioid Side Effects

Natural laxatives such as chia seeds, leafy greens and berries can be given by a doctor in case of extreme constipation. To relieve the symptoms of dry mouth, it is essential to remain hydrated by increasing the intake of water. If the medication is causing drowsiness, it should be taken during the night-time, when the user does not have to partake in chores or other activities. In the case of abuse, one should enroll in the addiction treatment program. This is considered as the best step to overcome it. Treatment facilities provide a range of detox programs and further recovery therapies at reputable rehab.

Page Sources

  1. Ajo R, Segura A, Inda MD, Margarit C, Ballester P, Martínez E, Ferrández G, Sánchez-Barbie Á, Peiró AM, Erectile dysfunction in patients with chronic pain treated with opioids, 2017, https://www.ncbi.nlm.nih.gov/pubmed/28236471
  2. Mary Mallappallil, Jacob Sabu, Eli A. Friedman, Moro Salifu, What Do We Know about Opioids and the Kidney?, 2017, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5297852/
  3. The Guardian, US drug overdose deaths rose to record 72,000 last year, data reveals, https://www.theguardian.com/us-news/2018/aug/16/us-drug-overdose-deaths-opioids-fentanyl-cdc

Published on: September 17th, 2019

Updated on: May 5th, 2020

About Author

Peter J. Grinspoon, MD

Dr. Peter Grinspoon is an experienced physician with long-term clinical practice experience. As a former analgesic addict, Dr. Grinspoon knows precisely how important it is to provide patients with effective treatment and support. Medical writing for him is the way to communicate with people and inform them about their health.

Medically Reviewed by

Michael Espelin APRN

8 years of nursing experience in wide variety of behavioral and addition settings that include adult inpatient and outpatient mental health services with substance use disorders, and geriatric long-term care and hospice care.  He has a particular interest in psychopharmacology, nutritional psychiatry, and alternative treatment options involving particular vitamins, dietary supplements, and administering auricular acupuncture.


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