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Narcotic analgesics

Medically reviewed by C. Fookes, BPharm Last updated on Feb 28, 2018.

Other names: narcotics, opiates, opioid analgesics, opioids

What are narcotic analgesics?

Narcotic analgesics are a class of medicines that are used to provide relief from moderate-to-severe acute or chronic pain. They may also be called opiates, opioid analgesics, or narcotics. Analgesic is another name for a medicine that relieves pain.

Narcotic analgesics are one of the most widely used analgesics for pain relief; however, they have been overused, overprescribed, and misused which has resulted in more than two million people in the U.S. alone having a substance misuse disorder involving prescription narcotic analgesics.

Narcotic analgesics work by binding to opioid receptors, part of the opioid system that controls pain, pleasurable and addictive behaviors. Opioid receptors are more abundant in the brain and spinal cord but are also located elsewhere in the body such as the stomach and the lungs. The main opioid receptor that narcotic analgesics bind to is the mu receptor.

What are narcotic analgesics used for?

In the past, narcotic analgesics have been used for all types of pain, which may explain why there are so many people addicted to them today.

The most appropriate use of narcotic analgesics is for the relief of short-term, intense pain, such as that occurring immediately after surgery or due to a medical condition.

Narcotic analgesics are also appropriate for the relief of pain due to cancer, or for palliative care or end-of life care. However, they should only be considered to treat other types of chronic pain under strict conditions and with close monitoring.

What are the differences between narcotic analgesics?

Narcotic analgesics differ in their structure, potency, and the way they are absorbed, distributed, metabolized and excreted within the body.

Some, like morphine and codeine were originally derived from plants. Others, such as heroin, hydrocodone, hydromorphone, oxycodone and oxymorphone were made by modifying morphine and are called semi-synthetic. There are three main classes of opioids – those that are structurally like morphine (the phenanthrenes), those that resemble fentanyl (the phenylpiperidines), and those that resemble methadone (the phenylheptylamines).

Different narcotic analgesics have different potencies, based on how strongly they bind to the opioid receptor (for example, fentanyl is 80 to 100 times stronger than morphine). This means that dosages for one narcotic may be significantly different from another. Although conversion charts exist (these tell you what dose of a narcotic compares to the equivalent analgesic dose of morphine), these are only at best a guide because other variables, such as an individual’s genetics, also play a part in how a person responds to a narcotic.

If a narcotic analgesic is deemed appropriate, codeine or tramadol should be tried first if the pain is mild-to-moderate. If the pain is unresponsive to these analgesics, or for more severe pain, then hydromorphone, morphine, or oxycodone should be considered. Fentanyl and methadone should only be used for severe pain that is unresponsive to other narcotic analgesics.

Common narcotic analgesics available in the U.S. include:

Name Route Onset of effect Duration of effect
alfentanil Intravenous (IV) 90 seconds 45-60 mins
codeine Oral 15-60 mins 3-4 hours
fentanyl IV Immediate 0.5-1h
Intramuscular (IM) 7-8 mins 1-2 hours
Buccal (through the gums)
Sublingual (SL)
5-15mins 4-6 hours
Transdermal patch (via the skin) 6h 72-96 hours
hydrocodone Oral 10-20 minutes 4-8 hours
hydromorphone Oral 15-30 mins 3-4 hours
IV 5 mins 3-4 hours
methadone Subcutaneous (SC) (under the skin) 15 mins 3-4 hours
morphine Oral 30-60 mins 3-6 hours (immediate-release)
8-24 hours (extended-release)
IV/SC 5-10 mins 4 hours
oxycodone Oral 10-15 mins 3-6 hours
oxymorphone Oral 30-60 mins (immediate-release)
1-2 hours (extended-release)
4-6 hours (immediate-release)
12 hours (extended-release)
IM/IV/SC 5-10 mins 3-6 hours
tramadol Oral 30-60 mins (immediate-release)
1-2 hours (extended-release)
4-6 hours (immediate-release)
24 hours (extended-release)

Are narcotic analgesics safe?

There are serious risks associated with narcotic analgesics including respiratory depression (unusually slow and shallow breathing), opioid-use disorder, and potentially fatal overdose.

Opioid-use disorder is defined as the repeated occurrence of at least two out of 11 specific opioid-associated problems, including using opioids in increased amounts or for longer than intended; continued use despite interference with daily activities; or still using while in hazardous situations. Severe opioid-use disorder is defined as a cluster of 6 or more problems and it can affect people from all educational and socioeconomic backgrounds.

Narcotic analgesics are potentially addictive and the risk of becoming emotionally and physically dependent on them increases the more you take and the longer you take them for. When prescribed by a doctor and used for short periods of time, such as for less than five days for pain relief after surgery, the risk of becoming addicted to narcotic analgesics is relatively low.

The number of fatal overdoses from opioids continues to rise and this has resulted in government officials introducing new legislation to further restrict the prescribing of opioids. More than 42,000 people died in 2016 because of an opioid overdose; 40% of these deaths involved a prescription narcotic analgesic.

When taken exactly as prescribed by a doctor, for short periods of time, for the relief of severe pain, and under strict monitoring, narcotic analgesics are considered acceptable to use. However, they may still be associated with some severe side effects, despite proper use.

What are the side effects of narcotic analgesics?

Narcotic analgesics have many side effects, although people with cancer or terminal illness taking narcotics for long periods of time may become tolerant to some of these side effects.

Drowsiness, sleepiness, or dizziness is common with most narcotic analgesics. This can affect driving or a person's ability to operate machinery and perform other hazardous tasks. Alcohol may potentiate these effects.

Other commonly reported side effects include:

Withdrawal symptoms may occur when people who have been taking narcotic analgesics abruptly stop taking them. Symptoms are like having the flu, and may include body aches, chills, depression, diarrhea, goose-bumps, headaches, high blood pressure, insomnia, irritability, a runny nose and sweats. Withdrawal symptoms usually last about a week.


  1. Opioid Addiction. 2016 Facts & Figures. American Society of Addiction Medicine.
  2. Drewes AM, Jensen RD, Nielsen LM, et al. Differences between opioids: pharmacological, experimental, clinical and economical perspectives. British Journal of Clinical Pharmacology. 2013;75(1):60-78. doi:10.1111/j.1365-2125.2012.04317.x.
  3. Canadian Guideline for Safe and Effective Use of Opioids for Chronic Non-Cancer Pain Michael G. DeGroote. National Pain Centre. McMaster University.
  4. Fentanyl Effentora 100 mcg Buccal Tablets. EMC. TevaPharmaBC
  5. Rational Opioid use. Stanford Education 2008.


List of Narcotic analgesics:

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Drug Name Reviews Avg. Ratings
meperidine systemic (Pro)
73 reviews
opium systemic (Pro)
20 reviews
methadone systemic (Pro)
519 reviews
hydromorphone systemic (Pro)
388 reviews
codeine systemic (Pro)
44 reviews
fentanyl systemic (Pro)
366 reviews
oxycodone systemic (Pro)
829 reviews
oxymorphone systemic (Pro)
211 reviews
nalbuphine systemic (Pro)
31 reviews
morphine systemic (Pro)
326 reviews
butorphanol systemic (Pro)
65 reviews
levorphanol systemic (Pro)
19 reviews
buprenorphine systemic (Pro)
568 reviews
propoxyphene systemic (Pro)
23 reviews
tramadol systemic (Pro)
1,430 reviews
tapentadol systemic (Pro)
379 reviews
pentazocine systemic (Pro)
9 reviews
hydrocodone systemic (Pro)
165 reviews
alfentanil systemic (Pro)
0 reviews
remifentanil systemic (Pro)
0 reviewsAdd rating
sufentanil systemic (Pro)
0 reviewsAdd rating

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.