How Do Painkillers Work And What Are Pain Meds Made Of?

Last Updated: March 24, 2024

Roger Weiss Authored by Roger Weiss, MD
David Levin Reviewed by David Levin
0 sources cited

Pain-relieving medications are used to achieve analgesia and taking for reducing or relieving headaches, toothaches, muscle spasm, arthritis, after surgery, and other aches and pains. What do painkillers do? Pain medications relieve pain without altering sensory awareness and consciousness or blocking the conduction of nerve impulses. Painkillers act in various ways: peripherally and centrally.

How Are Painkillers Made?

What are painkillers and analgesic medications made of and how? There are many types of analgesics medications with different ingredients, as well as the methods they have been delivered or extracted. These factors influence their mechanism of action in the body, usage, possible side effects, and even legality of use.

Ingredients Of Painkillers

What are painkillers made of? The OTC painkillers include acetaminophen and NSAIDs such as:

  • aspirin
  • ibuprofen
  • ketoprofen
  • Naproxen
  • diclofenac
  • mefenamic
  • acid
  • indomethacin
  • celecoxib
  • etoricoxib

The prescription opioids ingredients in painkillers include oxycodone, codeine, tramadol, morphine, hydrocodone, meperidine, hydromorphone, and propoxyphene.

Painkillers Obtaining Methods

How are painkillers made? The non-opioid painkillers such as NSAIDs and acetaminophen are synthetically derived from aspirin, but opiate painkillers may be obtained naturally, semi-synthetically, and synthetically. The natural opiate painkillers are extracted from the poppy opium plant such as morphine. Semi-synthetic drugs are the derivatives of opium alkaloids such as:

  • benzylmorphine
  • ethylmorphine
  • heroin
  • desomorphine
  • allopseudocodeine
  • heterocodeine
  • isocodeine
  • pseudocodeine
  • dihydrocodeinone
  • dihydrohydroxycodeinone

The synthetic form of opiates includes pethidine, methadone, and dithienylbutenylamine.

There are also natural herbal painkillers that are considering as alternatives for OTC painkillers for treating mild pain, such as oils, spices, plants, berries, and seeds.

natural alternatives to painkillers

How Do Painkillers Work In The Body?

How do painkillers work? Each group of these medications has a different mechanism of action.

Non-Steroidal Anti-Inflammatory Analgesics MOA

Non-steroidal anti-inflammatory drugs inhibit cyclooxygenase (COX), the enzyme that makes prostaglandins. Anti-inflammatory drugs such as toothache painkillers (Ibuprofen, Naproxen, and mefenamic acid), inhibit both cyclooxygenase 1 and 2. Celecoxib and etoricoxib are other groups of anti-inflammatory drugs, with selective inhibition of cyclooxygenase 2. Сelecoxib and etoricoxib are safer for a person who suffers from stomach inflammation or ulcer than non-selective one acidic NSAIDs.

Opioid Painkillers MOA

How does pain medication work when includes opioids? The MOA of opioid drugs such as morphine is by relieving pain through interacting with opioid receptors, which are distributed throughout the central nervous system (CNS). When opioid medications enter the blood and attach to opioid receptors, brain cells release signals that muffle the perception of pain.

Acetaminophen Mechanism Of Action

The exact mechanism of action of acetaminophen is not known, but it may increase the body’s pain threshold and also is considering as a weak inhibitor of the synthesis of prostaglandins. Acetaminophen is safer than opioids if taken at recommended doses and for a set period of time. However, it’s recommended to consult a doctor to find the safest pain medication for long term use.

Muscle relaxants, Antidepressants, and Anticonvulsants MOA

Some groups of medications, such as muscle relaxants, antidepressants, and anticonvulsants, may also relieve pain. The mechanism of action of muscle relaxants is by reducing pain centrally through their sedative action. Tricyclic antidepressants MOA is by increasing neurotransmitters in the spinal cord that reduce pain signals. The mechanism of action of anticonvulsant drugs is by relieving the pain of neuropathies, possibly through stabilizing nerve cells.

muscle relaxants for pain relieving

Do Other Substances Affect The Painkillers MOA?

What do painkillers do in the body when taken with alcohol? Alcohol dulls the feeling of pain, but affect how painkillers work. Drinking on painkillers may affect the MOA of these medications and increase the danger of its side effects. Alcohol may alter the binding of opiates to its opioids receptors. Can one take painkillers with antibiotics in the presence of an infection? It is safe to use some medications such as acetaminophen and ibuprofen at the same time with antibiotics, as most antibiotics not affect the mechanism of action of these medications.

Action Time For Painkillers

When Do Painkillers Start Working In The Body?

How long does it take for painkillers to kick in? The method of pain meds administration affects the period of time that painkillers take to start its effect in the body. When a person takes a tablet, it may give the effect within 30-60 minutes. The injectable pain medication can take a few minutes to get its effect. Pain meds effects appear very quickly while snorting them by some abusers.

What Is The Time Of Action For Pain Meds?

How long do painkillers take to work? The medications that are used for relieving pain may be immediately acting or long-lasting pain meds. The fast pain meds, such as OTC medications, start to work quickly after 1 hour of its administration, but they are useful for a shorter period of time. Extended-release pain meds release the drugs over a more extended period, such as oxycontin which is a time-released, 12-hour pain medication. How long does it take for painkillers to work while using extended-release analgesics? The extended-release pain medication may give its effect for a prolonged period of time, lasting for days.

Some opioid medications have immediate release action such as codeine, meperidine, tapentadol, oxycodone, and tramadol. The U.S. Food & Drug Administration implements a risk evaluation and mitigation strategy (REMS) for long-acting opioids to ensure that the benefits of these medications outweigh the risks. The extended-release pain medication list of opioids that required to have REMS is:

  • Oxymorphone Hydrochloride
  • Morphine Sulfate
  • Methadone Hydrochloride
  • Fentanyl

How long do painkillers stay in system after the MOA ends? The long-acting pain medication may stay in the body for up to 7 days. However, hair drug tests may determine the presence of long-lasting pain medication within 90 days after the medicine was taken.

If The Painkillers Don’t Work

These medications are useful and effective for the relief of different types of pain. On the other hand, there are various conditions that pain medications are not working:

  • Sometimes, pain and headache won’t go away with painkillers when used for a prolonged period of time.
  • Most painkillers do not work in people with a history of chronic migraines.
  • The OTC headache painkillers are not working in relieving physiological headache.
  • Sometimes, a headache that does not respond to painkillers is coming from the neck, not from the head. A doctor can advise taking OTC medication for mild pain caused by head injury and may prescribe a stronger medication for severe headache.
  • The painkillers may also not work with abnormal menstrual cramps. If there are suddenly cramps that won’t go away with painkillers, then it is a must to seek out a doctor for knowing the actual cause of these cramps.
  • Some drugs like the cytochrome P450 inducers, such as amiodarone, carbamazepine, and phenobarbital increase the metabolism of painkillers, decrease its serum level, and make them not work.

painkillers don't work

Be Educated About The MOA Of Painkillers

It is essential to know the MOA of each pain medication to avoid the dangerous adverse reactions that may occur while using it alone or in combination with other medicines. Every pain medication has a specific mechanism of action. Acetaminophen is a weak inhibitor of prostaglandin synthesis with a little side effect. Anti-inflammatory drugs such as ibuprofen and Naproxen are non-selective inhibitors of cyclooxygenase enzyme with increasing the possibility of gastritis and peptic ulcer. Other anti-inflammatory drugs such as celecoxib inhibit cyclooxygenase 2 only, which are more safe for gastric than non-selective anti-inflammatory inhibitors of cyclooxygenase.

However, chronic episodes of pain treated with opioids may lead to misusing them for an extended period and cause addiction, which will require searching for a rehabilitation center. There are many options for treating the addiction depending on several factors, including the type of painkillers, the length of use, and the level of harm.

Page Sources

  1. Graham GG, Scott KF. Mechanism of action of paracetamol. 2005.>
  2. Shelley Wiechman Askay, Charles H Bombardier, David R Patterson. Effect of acute and chronic alcohol abuse on pain management in a trauma center. 2009.>
  3. List of Extended-Release and Long-Acting Opioid Products Required to Have an Opioid REMS. US Food & Drug Administration. 2017.

Published on: September 25th, 2019

Updated on: March 24th, 2024


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  • Carla A. Prunty
    Your information was very impressive and to the point. I didn’t know there are so many drugs that could help but also become addicted to. I am 73 years old and for the first time in my life I had a knee replacement and now taking 5 mil of oxycondine. This information was very informative to understand my pill helping my pain. No matter how old you get there is more to learn! Thank you!!

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