Musculoskeletal

What are Non-steroidal anti-inflammatory drugs (NSAIDs)

• NSAIDs are heterogeneous group of drugs having analgesic, anti-inflammatory and antipyretic effect.
• Unlike morphine they do not depress CNS, do not produce physical dependence, have no abuse liability and are weaker analgesics.
• They are also called non-narcotic, non-opioid or aspirin like analgesics.
• They act primarily on peripheral pain mechanism, but also in the CNS to raise pain threshold.

Classification of NSAIDs based on chemical groups

• Salicylates: Sodium salicylate, Acetylsalicylic acid (aspirin), Methylsalicylate.
• Aniline or : Paracetamol (acetaminophen), Acetanilide, Phenacetin,
• p- Aminophenol derivatives: Aminopyrine, Antipyrine.
• Pyrazolone derivatives: Phenylbutazone, Oxyphenbutazone, Sulphinpyrazone.
• Indole & related drugs: Indomethacin, Sulindac.
• Phenyl acetic acid derivatives: Diclofenac.
• Propionic acid derivatives: Ibuprofen, Naproxen, Fenoprofen, Ketoprofen.
• Fenamates: Mefenamic acid.
• Oxicams derivatives: Piroxicam, Tenoxicam, Meloxicam.
• Sulfonanilide derivatives: Nimesulide.

Analgesic-antipyretic with poor anti-inflammatory action:

• p-aminophenol derivatives: Paracetamol (Acetaminophen).
• Pyrazolone derivatives: Metamizol.
• Benzoxacine derivatives: Nefopam.

Indications/why they are prescribed?

• Analgesia
• Antipyresis
• Anti-inflammatory
• Antithrombotic
• Closure of ductus arteriosus in newborn

Anti-inflammatory

• The inflammatory reactions such as vasodilatation, increased vascular permeability, cell proliferation, pain etc are mediated by the release of a multitude of chemical mediators having varied mechanisms of action.
• The inflammatory stimuli in the inflammatory cells induce synthesis of prostaglandins through COX2.
• The NSAIDS exert anti-inflammatory effect by inhibition of prostaglandin synthesis by irreversible inhibition of this enzyme.

Analgesics

• The NSAIDS are mainly effective against pain associated with arthritis, bursitis, muscular pain, vascular pain, toothache, dysmenorrhoea and bone pain, in all the conditions there is increased synthesis of pain inducers and prostaglandins.
• The prostaglandins sensitize nociceptors to pain inhibiting prostaglangin synthesis through irreversible inactivation of COX-1 or COX-2 or both.

Antipyresis

• Normal body temperature is maintained by thermoregulatory centre (thermostat) in hypothalamus, which ensures a balance between heat production and heat loss.
• Fever occurs due to disturbance in the hypothalamic thermostat, which is set at a high temperature.
• The antipyretics act by resetting the thermostat to normal set-point and then the body temperature regulating mechanisms (dilatation of superficial blood vessels, sweating and increased respiration, and promoting heat loss) operate to lower the elevated body temperature to normal level.
• Normal body temperature is not affected by NSAIDS or antipyretics (at therapeutic doses).

Antiplatelet Aggregator

• TXA2 is pro-aggregator (COX-1)
• PGI2 is anti-aggregator
• Most NSAIDs – effects on TXA2 predominates and inhibits aggregation – prolonged bleeding time
• Aspirin is highly active and acetylates COX in circulation – before hepatic 1st pass metabolism
• Even small dose Antithrombotic effect – Myocardial Infarction and other cardiac conditions

Examples:

Paracetamol, Ibuprofen, diclofenac Sodium, Diclofenac Potassium, Nimsulide, Aceclofenac, Piroxicam etc

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