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An analgesic, also known as a painkiller, is the term used for any member of the group of drugs used to relieve pain and to achieve analgesia — a painless state. Analgesic drugs act in various ways on the peripheral and central nervous system.
An analgesic, also known as a painkiller, is the term used for any member of the group of drugs used to relieve pain and to achieve analgesia — a painless state. Analgesic drugs act in various ways on the peripheral and central nervous system.
The pain relief induced by analgesics occurs either by blocking pain signals going to the brain or by interfering with the brain's interpretation of the signals. There are several groups of painkillers and they include:
  • Paracetamol (acetaminophen)
  • Nonsteroidal anti-inflammatory drugs (NSAIDs) such as salicylates
  • Narcotic drugs such as morphine
  • Synthetic drugs with narcotic properties such as Tramadol and others. [1]
Some other classes of drugs, which normally don’t belong to the group of pain killers, are used to treat some types of pain and these include tricyclic antidepressants and anticonvulsants.
Some experts include Aspirin and other non-steroidal anti-inflammatory drugs in the class of analgesics because they have some analgesic properties, but they primarily have an anti-inflammatory effect. 

Groups of Pain Killers

Simply put, analgesics are a class of drugs used to relieve pain. There are two kinds of analgesics [1]:
  • Non-narcotics
  • Narcotics

Non-Narcotic Analgesics


Most people already know that Paracetamol or Acetaminophen is the most commonly used over-the-counter, non-narcotic analgesic. It is extremely popular painkiller because it is both effective for mild to moderate pain relief. It is also relatively inexpensive. Although not too many people take this drug seriously, it is proven that, if acetaminophen is not used according to directions, serious side effects can occur. The most common side effect is the increase the risk of liver damage, which increases if a patient ingests alcohol. This medication can be found in combination with other active ingredients in many cold, sinus, and cough medications. [2]

Narcotic Analgesics

Everyone should know that there are two types of narcotic analgesics: the opiates and the opioids. Opiates are the alkaloids found in opium. Opioids are any medication which binds to opioid receptors in the central nervous system or gastrointestinal tract. [3]
They are used in medicine as strong analgesics, for relief from severe or chronic pain. What's interesting is that there is no upper limit for the dosage of opioids used to achieve pain relief, but the dose must be increased gradually to allow for the development of tolerance to adverse effects.
There are four broad classes of opioids:
  • Endogenous opioid peptides are normally produced in the body and include endorphins, dynorphins, and enkephalins.
  • Opium alkaloids: the most common ones are morphine, codeine, and thebaine
  • Semi-synthetic opioids: The most common are heroin, oxycodone, hydrocodone, dihydrocodeine, hydromorphone, oxymorphone, and nicomorphine.
  • Fully synthetic opioids: The most common are Demerol, Methadone, Fentanyl, propoxyphene, pentazocine, buprenorphine, butorphanol, and Tramadol.


It is important to point out that Oxycodone is a potent and addictive opioid analgesic medication. It is synthesized from thebaine. Its name is derived from codeine because the chemical structures are very similar. Oxycodone is one of the most powerful medications for pain control that can be taken orally and it is also used in the treatment of moderate to severe chronic pain. OxyContin is available in 5, 10, 20, 40, 80, and 160 mg tablets, and it is effective for 8 to 12 hours. What's most important is that in the United States, oxycodone is a type II controlled substance. [4]


Probably everyone knows that Morphine is an extremely powerful opiate analgesic drug. It represents an active ingredient of opium. It should be pointed out that, like other opiates, morphine acts directly on the central nervous system to relieve pain. Target tissues are synapses of the arcuate nucleus in the brain. Several side effects can occur and the most common are:
  • Impairment of mental performance
  • Euphoria
  • Drowsiness
  • Lethargy
  • Blurred vision
  • Constipation
The most important thing there is to know about this drug is that it is highly addictive when compared to other substances. Tolerance and physical and psychological dependence develop extremely quickly. [5


Tramadol is an atypical opioid which is a centrally acting analgesic, used for treating moderate to severe pain. What makes Tramadol so unique? Besides the fact that it is a synthetic agent, it also appears to have actions on the GABAergic, noradrenergic and serotonergic systems, which isn't the case with other pain killers! Tramadol is available in both injectable and oral preparations. Dosages vary depending on the degree of pain experienced by the patient, but it is useful to know that Tramadol is approximately 10% as potent as morphine. Oral doses range from 50–400 mg daily, with up to 600 mg daily when given IV/IM. [6]


Codeine is a narcotic analgesic painkiller used for pain relief. The drug codeine is also used in combination medications with the drug acetaminophen, in brand names such as Tylenol, Tylenol with Codeine, Empirin and Phenaphen with Codeine, or in a drug combination with Aspirin. Codeine is used for treating moderate to mild pain. [7]


Darvocet is a combination narcotic analgesic painkiller used for pain relief. Other brand name drugs which contain propoxy and acetaminophen include Propacet and Wygesic. Darvocet is very useful for treating all kind of pains, but the problem is that there are several possible side effects related to the use of this medication. [8]


Two medications, Darvon and PP-Cap (generic drug name propoxyphene), are narcotic analgesic painkillers used for pain relief. It is important to point out that the propoxyphene comes as a tablet, capsule, and liquid to take by mouth. Darvocet contains the drugs Propoxyphene and acetaminophen. [9]


Duragesic is a narcotic analgesic painkiller used for severe pain relief. It is important to know that Duragesic comes only as a skin patch, which contains the generic drug Fentanyl. The medication is absorbed directly from the patch when it's applied to the skin. [10]


The debate over the use of marijuana for medical purposes has been ongoing for years. Marijuana has been hailed as a prescription for many conditions and physicians once used it to stimulate appetite, relieve chronic pain, treat asthma and migraines. Most common indications for Marijuana use are [11]:
  • Chronic pain
  • Migraines
  • Glaucoma
  • Multiple sclerosis and many others. 
Many young users say that addiction to marijuana isn't possible. Of course, this isn't true! Addiction is highly possible! Long-term marijuana use can lead to addiction for some people, which means that they use the drug compulsively even though it interferes with family, school, work, and recreational activities. When a person is chemically dependent on marijuana, it means that the person needs to use more and more to get the same effect. The most common withdrawal symptoms are depressed feelings, trouble sleeping, and nausea.

Salicylic acid

Salicylic acid is a colorless, crystalline organic carboxylic acid. Salicylic acid functions as a plant hormone. It is important to point out that salicylic acid is toxic if ingested in large quantities. In small amounts, salicylic acid is used as a food preservative and antiseptic in toothpaste. The medicinal properties of salicylates have been known since ancient times since the substance occurs in the bark of willow trees. [12]
Aspirin can be prepared by the esterification of the phenol hydroxyl group of salicylic acid. It is often combined with Bismuth and when combined the two key ingredients help control diarrhea, nausea, heartburn, and even gas. It is also very mildly antibiotic.

Side Effects and Adverse Reactions of Opioids:

Common side effects and adverse reactions [13]:
  • Nausea
  • Orthostatic hypotension  
  • Urinary retention
  • Vomiting
  • Drowsiness
  • Dry mouth
  • Miosis 
Less common side effects and adverse reactions:
  • Bradycardia (slow heart rate)
  • Tachycardia (rapid heart rate)
  • Raised intracranial pressure
  • Confusion
  • Hallucinations
  • Delirium
  • Hives
  • Itch
  • Hypothermia ureteric or biliary spasm
  • Muscle rigidity
  • Flushing
  • Respiratory depression
  • Fatal overdose

Pros and Cons of the Use of Pain Killers

There have been debates over the addictive potential of opioids vs the benefit of their analgesic properties, in particular for treating non-malignant chronic pain, such as chronic arthritis. Although they can be beneficial, several possible lethal side effects can occur! 
Some experts believe opioids can be taken safely for years with minimal risk of addiction or toxic side effects, but this is possible only if taken under close supervision of your doctor!