Effects of Opioids

Please note that this is by no means a complete comprehensive list of all possible effects of opioid drugs. With any drug, not only opioids, effects are subjective for each user and can vary greatly between users. Also be aware that while most of the effects listed on this page apply to all opioid drugs, each opioid is unique and there are subtle variations and differences in effects between different opioids. For example, a certain opioid may be more euphoric compared to other opioids, or it may cause nausea more often than others, etc.

Please also note that the effects from a small amount of drugs on a non-addict are almost in no sense comparable to their effects upon an addict. The effects that an addict will experience are in many respects quite the opposite of the effects experienced by an opioid-naive patient. The pleasure that is usually felt the first several times opioids are administered diminishes as the same dose becomes less and less effective over time.

Visit this link (Addiction & Opiates: Chapter 1, by Alfred R. Lindesmith) if you would like to get a better understanding of the effects opioids have on addicts and how these effects change as addiction progresses.

Short Term Effects


  • analgesia (reduction of pain)
  • nausea, vomiting
  • constipation
  • sedation, sleepiness, drowsiness
  • itching
  • dry mouth
  • sweating
  • cough suppression
  • miosis (pupil constriction)


  • rash
  • abdominal pain
  • hiccups
  • difficulty breathing
  • difficulty swallowing
  • confusion/disorientation

Less common

  • anxiolysis (reduction of anxiety)
  • euphoria, mood improvement
  • relaxation
  • urinary retention
  • lightheadedness
  • sleeplessness/insomnia
  • fatigue/weakness
  • dizziness/headache
  • flushing
  • loss of appetite
  • nervousness/anxiety

Effects from overdose/extremely high dose

  • bradycardia (slow heart rate)
  • hypotension (low blood pressure)
  • seizures/convulsions
  • circulatory collapse
  • respiratory arrest
  • hallucinations/delirium
  • cold, clammy skin
  • tinnitus

Long-term Effects

  • addiction
  • tolerance
  • physical and psychological dependence
  • weakened immune system
  • subnormal testosterone levels in males
  • erectile dysfunction in males
  • opioid-induced hyperalgesia/opioid-induced abnormal pain sensitivity

Effects of IV Opioid Drug Use

The following list of problems are not caused by opioid drugs themselves, but are specific problems and risks associated with intravenous (IV) administration of drugs. Non-sterile conditions and improper injection techniques as well as reusing and sharing needles can all increase the risk of, or result in any of the following:

  • infection and abscesses
  • contracting blood-borne disease (e.g. HIV, hepatitis)
  • collapsed veins, track marks
  • arterial damage
  • social stigma attached to IV drug use
  • cotton fever


  • Benyamin R, Trescot AM, Datta S, Buenaventura R, Adlaka R, Sehgal N, Glaser SE, Vallejo R. Opioid complications and side effects. Pain Physician Mar 2008; 11(2 Suppl):S105-20. [PubMed] [PDF]
  • Opioids for persistent pain: Information for patients. British Pain Society, 2010. [PDF]
  • Angst MS, Clark JD. Opioid-induced hyperalgesia: a qualitative systematic review. Anesthesiology Mar 2006; 104(3):570-87. [PubMed] [PDF]
  • Vella-Brincat J, Macleod AD. Adverse effects of opioids on the central nervous systems of palliative care patients. Journal of Pain and Palliative Care Pharmacotherapy 2007; 21(1):15-25. [PubMed] [PDF]
  • Mathers BM, Degenhardt L, Phillips B, Wiessing L, et al. Global epidemiology of injecting drug use and HIV among people who inject drugs: a systematic review. The Lancet Nov 2008; 372(9651):1733-45. [PubMed]
  • Coughlin PA, Mavor AI. Arterial consequences of recreational drug use. European Journal of Vascular and Endovascular Surgery Oct 2006; 32(4):389-96. [PubMed] [PDF]

Related Pages

  • What are Opiates?
    Discover the history behind opiates, learn the difference between opiates and opioids, and read about where they come from.
  • Types of Opioids
    Learn about the three classes of narcotic, painkilling opioids: natural, synthetic, and semi-synthetic, as well as the other classes of opioids, including the endogenous opioids that are produced by our own bodies.
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