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Demerol Side Effects: Common & Rare Risks to Look For

Peter Manza, PhD profile image
Reviewed By Peter Manza, PhD • Updated Aug 23, 2023 • 8 cited sources

Common side effects of Demerol include nausea, vomiting, dizziness, constipation and drowsiness. Risks that are less common but very dangerous include respiratory depression, cardiac changes and seizures.  

When using Demerol, it is critically important to be aware of potential side effects and risks that may arise. While some side effects are common and mild, others are rare but much more severe.

Understanding the range of risks associated with Demerol use is important for informed decision-making and proactive management of the medication regimen.

What Are the Common Side Effects of Demerol?

There are a number of common side effects that can occur when Demerol is used. In most cases, these fade as the body gets used to the drug, but in other cases, they can be overwhelming enough to be disruptive to the ability to function. If side effects become an issue while using Demerol, even if they are common, reach out to your doctor to address the situation.

Common side effects of Demerol use include the following:[1]

  • Drowsiness or sedation: feeling excessively sleepy or lacking alertness
  • Vomiting: unpleasant sensations in the stomach, potentially leading to vomiting
  • Dizziness: feeling lightheaded or unsteady
  • Constipation: difficulty or infrequency in bowel movements
  • Dry mouth: reduced saliva production, resulting in a dry sensation in the mouth
  • Itching or rash: skin irritation or itchiness
  • Headache: aching or discomfort in the head
  • Confusion or cognitive impairment: difficulty thinking clearly or reduced mental sharpness

What Are the More Uncommon Side Effects of Demerol Use?

While rare, Demerol can potentially cause more certain severe side effects that indicate a serious problem and should be addressed immediately with emergency medical treatment.

Uncommon Demerol side effects include the following:[2],[3].[4],[5]

  • Seizures: In rare instances, Demerol use can trigger seizures, which are sudden, uncontrollable electrical disturbances in the brain. People who have a history of seizures or certain medical conditions may be at higher risk of experiencing this issue when taking Demerol. 
  • Respiratory depression: Demerol can depress the central nervous system, potentially causing slowed or shallow breathing, an issue that requires immediate medical attention.
  • Allergic reactions: Although rare, some people may experience allergic reactions to Demerol, resulting in symptoms such as difficulty breathing, swelling, rash, or hives. Allergic reactions require prompt medical attention.
  • Serotonin syndrome: Demerol can interact with other medications, such as certain antidepressants, and contribute to a rare condition known as serotonin syndrome. Symptoms may include agitation, rapid heartbeat, high blood pressure, fever, sweating, tremors and muscle stiffness.
  • Adrenal insufficiency: Prolonged use or abrupt discontinuation of Demerol can potentially affect the function of the adrenal glands, leading to adrenal insufficiency. This condition can cause symptoms like fatigue, weakness, weight loss and low blood pressure.
  • Cardiac effects: Demerol use may have effects on the cardiovascular system, including changes in heart rate and blood pressure. While rare, serious cardiac events such as irregular heartbeat or heart attack have been reported.

What Are Some of the Dangerous Interactions With Demerol? 

Demerol is not recommended for people with certain conditions or who are taking some medications, as dangerous interactions can occur. Demerol should not be taken when the following medications are being used:

  • Central nervous system depressants: Combining Demerol with other substances that have sedating effects — such as alcohol, benzodiazepines (like Xanax or Valium), or barbiturates — can lead to excessive sedation, respiratory restriction and even coma, which can be life-threatening.
  • Serotonergic medications: Taking Demerol alongside serotonergic medications — such as selective serotonin reuptake inhibitors (SSRIs), serotonin norepinephrine reuptake inhibitors (SNRIs), or certain antidepressants — can increase the risk of serotonin syndrome.[6] This condition is characterized by a potentially dangerous buildup of serotonin in the body.
  • Monoamine oxidase inhibitors (MAOIs): Concurrent use of Demerol and MAOIs, which are used to treat depression and other conditions, can lead to a severe reaction like serotonin syndrome or hypertensive crisis.[7] This combination can cause a dangerous increase in blood pressure.
  • Serotonergic herbal supplements: Certain herbal supplements, such as St. John’s wort and 5-HTP, can also increase serotonin levels, which again can increase the risk of developing serotonin syndrome.
  • MAO inhibitors: Using Demerol within two weeks of taking an MAO inhibitor can lead to a life-threatening condition known as a hypertensive crisis, a condition characterized by a sudden and severe increase in blood pressure.

Potential Risks & Warnings for Demerol Use

Demerol is a potent and powerful opioid, making it a target for misuse and the development of opioid use disorder (OUD). Unlike other medications that can trigger a physical dependence with prolonged use, Demerol can also cause a psychological dependence that combines with the physical dependence to create OUD in users. 

Physical dependence is normal and an issue that occurs with regular use of many substances over time. 

After months or years of use, the dosage may not have the same medical effect, causing the person to need a higher dose in order to experience the desired result. This is known as developing a tolerance to Demerol. Once dependence has formed, withdrawal symptoms will occur when the body’s level of Demerol drops below the now “normal” amount. 

Withdrawal symptoms are uncomfortable and even painful, akin to feeling sick with a bad flu. In order to avoid this feeling, many people develop compulsive drug-seeking behaviors that ultimately lead to dependence on the drug. [8]

When Demerol is used outside the bounds of a prescription, the development of an OUD is more likely, and the risk of overdose and death increases. Though most medical professionals who prescribe the drug are careful to monitor their patients’ use of the substance, it is very possible to develop an OUD to medically prescribed Demerol, especially if the pills are misused. 
Misuse of Demerol is characterized by taking more of the drug than prescribed, combining the pills with alcohol or other sedatives, and crushing the pills before use.

Getting Help for OUD

If you’re facing an OUD related to Demerol, it’s important to seek professional help as you begin the process of navigating your recovery. One of the most effective forms of treatment for opioid use disorder is Medication for Addiction Treatment (MAT), which highlights the use of medication like Suboxone in addition to recommended individual and group therapies.[9]

To begin your addiction treatment journey, reach out to a healthcare professional or addiction specialist who can evaluate your needs and create a personalized plan of care. At Bicycle Health, we offer comprehensive Suboxone treatment for opioid use disorder via telehealth services, making the process easy and affordable. Call now to get started today on building the foundation for a better tomorrow.

Reviewed By Peter Manza, PhD

Peter Manza, PhD received his BA in Psychology and Biology from the University of Rochester and his PhD in Integrative Neuroscience at Stony Brook University. He is currently working as a research scientist in Washington, DC. His research focuses on the role ... Read More

  1. Demerol (meperidine hydrochloride). FDA Insert. March 2021. Accessed July 2023.
  2. Seizure. StatPearls. February 2023. Accessed May 2023.
  3. Opioid-Induced Respiratory Depression: Reversal by Non-Opioid Drugs. F1000Prime Reports. September 2014. Accessed May 2023.
  4. Adrenal Insufficiency. The Ochsner Journal. February 2023. Accessed May 2023.
  5. Selective Serotonin Reuptake Inhibitors. StatPearls. February 2023. Accessed May 2023.
  6. Monoamine Oxidase Inhibitors (MAOI). StatPearls July 2022. Accessed May 2023.
  7. Compulsive Drug-Seeking Behavior and Relapse. Neuroadaptation, Stress, and Conditioning Factors. Annals of the New York Academy of Sciences. June 2001. Accessed May 2023. 
  8. Information About Medication-Assisted Treatment (MAT). U.S. Food and Drug Administration. May 2023. Accessed May 2023.

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