Drugs Home > Side Effects of Meperidine

Potential side effects of meperidine include facial flushing, lightheadedness, vomiting, and dry mouth. In many cases, side effects of the medication are minor and either do not require medical attention or can be treated easily. However, certain side effects are potentially serious and should be reported to your healthcare provider immediately, including slow or irregular breathing, muscle twitches, or disorientation.

An Introduction to Meperidine Side Effects

As with any medicine, meperidine hydrochloride (Demerol®) can cause side effects. However, not everyone who takes the medication will experience problems. In fact, some people tolerate it quite well. If side effects do occur, in many cases, they are minor and either require no treatment or can easily be treated by you or your healthcare provider.
(This article covers many, but not all, of the possible side effects with meperidine. Your healthcare provider can discuss a more complete list of meperidine side effects with you.)

Serious Side Effects Seen With Meperidine

Some side effects with meperidine are potentially serious and should be reported immediately to your healthcare provider. These include, but are not limited to:
  • Agitation, disorientation, or hallucinations
  • Shakiness, seizures, muscle twitches, or other abnormal muscle movements
  • A slow heart rate (bradycardia) or fast heart rate (tachycardia)
  • Low blood pressure (hypotension) or high blood pressure (hypertension)
  • Fainting
  • Signs of serotonin syndrome, such as:


    • Confusion or other mental changes
    • A rapid heart rate
    • Nausea
    • Vomiting
    • Diarrhea
    • Hallucinations
    • Blood pressure changes
    • Overactive reflexes
    • Fever
    • Shivering
    • Shakiness
    • Agitation
    • Sweating
    • Seizures
    • Coma


  • The urge to take more meperidine than prescribed or for a non-medical purpose
  • Difficulty passing urine
  • Slow or irregular breathing
  • Chest pain or heart palpitations
  • Signs of an allergic reaction, such as:


    • An unexplained rash
    • Hives
    • Itching
    • Swelling of the mouth or throat
    • Wheezing
    • Difficulty breathing.


Many of the serious side effects of meperidine are due to a toxic metabolite of the medication. This metabolite (known as normeperidine) is a byproduct of meperidine that stays in the body much longer than meperidine itself. If repeated doses of meperidine are taken, normeperidine builds up and can cause serious side effects.
Written by/reviewed by:
Last reviewed by: Kristi Monson, PharmD;
Last updated/reviewed:
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