Simple Analgesics

Time Required: 
5 minutes

Learning Outcomes:

  • to have a basic understanding what simple analgesics are and to be able to recognise different types of NSAIDS
  • to understand the basic mechanism of action of simple analgesics
  • to be aware of the risks associated with taking NSAIDS

Simple Analgesics

Simple, or non-opioid analgesics, are a wide ranging group of drugs that comprises of non-steroidal anti-inflammatory drugs (NSAIDS) and paracetamol. Both paracetamol and most NSAIDS have antipyretic (fever reducing) properties, however, only NSAIDS have antiplatelet (anti-clotting) and anti-inflammatory effects. Due to its minimal side effects and ability to be tolerated by a large proportion of the population (very young to the very old), paracetamol is the first analgesia of choice for treating mild to moderate pain.

Many NSAIDS and paracetamol are available as over the counter medications and are available as a tablet, capsule, liquid, suppository or topical preparation. Intravenous paracetamol has recently become available in the hospital setting and has been demonstrated to be effective whilst causing minimal side effects. However, this should only be used when the oral route of administration is unavailable. Certain NSAIDS and higher potencies can also be obtained with a medical prescription. Examples of NSAIDS are:

  • Ibuprofen (prescription not required)
  • Diclofenac (prescription required for certain routes )
  • Aspirin (prescription not required)
  • Meloxicam (prescription required)
  • Naproxen (prescription required)

Only one NSAID should be used at one time. Combining different NSAIDS, or different routes of the same NSAID (oral and topical) does NOT increase the efficacy of the analgesics but does greatly increase the risk of side effects and is therefore NOT RECOMMENDED.

Indication for NSAIDS & paracetamol

Indication for NSAIDS & paracetamol

  • mild to moderate pain
  • fever
  • period pain
  • migraine and tension headache
  • osteoarthritis and rheumatoid arthritis, including juvenile rheumatoid arthritis
  • pain caused by cancer, particularly bone cancer
  • post-operative pain
  • trauma
  • in combination with opioid analgesics for moderate to severe pain

Mechanism of action

NSAIDS reduce pain and inflammation within the body by reducing the production of prostaglandins (pro-inflammatory chemicals). Prostaglandins are pro-inflammatory chemicals which are normally produced by the body as a consequence of tissue damage and have a significant role in the processes of inflammation, pain and fever.  Many of the effects of NSAID’s can therefore be attributed to the inhibition of prostaglandin synthesis. Prostaglandins are released by the damaged tissue, i.e. at the source of the pain, therefore NSAID’s are described as peripherally acting analgesics [1]. However, prostaglandins also have a protective function (gastric, renal support & platelet activation).

Until recently it was unclear the exact mechanism by which paracetamol works, however, recent evidence suggests that paracetamol also works by reducing the synthesis of specific prostaglandins [2].

Efficacy of simple analgesics

NSAIDS and paracetamol are very effective in the management of mild to moderate pain. Furthermore, evidence suggests that when simple analgesics are combined with stronger analgesics (e.g. opioids) they work synergistically together to reduce the amount of overall painkillers required and reduce the amount of side effects experienced. Simple analgesics should therefore form the basis of any pain management strategy. Further information on this can be obtained from the article 'WHO Analgesic Ladder'.

Precautions

NSAIDS should be used with caution with the following patients and expert opinion sought prior to prescribing in those with:

  • known allergy to any NSAID or paracetamol
  • asthma - in a small number of asthmatics anti-inflammatory medicines can trigger an asthma attack.
  • crohns disease – NSAIDS can exacerbate this condition
  • history of gastric irritation, including any ulceration of the gastric tract as NSAIDS significantly increase the risk of further ulceration and bleeding
  • renal impairment
  • dehydration
  • hypotension
  • heart failure and high blood pressure
  • pregnant patient
  • children should not use aspirin as there is a potential risk of Reyes Syndrome
  • 65 years and over
  • concomitant use of medications i.e. steroids and anti-coagulants
  • prolonged use of maximum dose.

Side effects of simple analgesics

Most common side effects of NSAIDS are mild and patients may not experience any side effects at all, particularly if only taking for a sort time (less than 3 days). However some side effects, though rare, are potentially life threatening (ulceration of gastric tract, renal failure) and so patients should always be monitored closely whilst taking NSAIDS. The risk of side effects associated with NSAID usage increases with age and therefore caution is advised in the elderly with an in-depth risk benefit analysis undertaken before commencing.

The most significant side effects associated with NSAID usage are [3]:

  • Gastric irritation/haemorrhage
  • Bronchospasm
  • Inhibition of platelet aggregation
  • Renal impairment

Reports of side effects with paracetamol when taken at the recommended doses are very rare.


References

  1. Pleuvry, B.J., 2005. Non-opioid analgesics. Anaesthesia & intensive care medicine, Anaesthesia & intensive care medicine 6, 25 - 29.
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