Nonsteroidal Anti-inflammatory Drugs and Antipyretic-Analgesics

All drugs grouped in this class have analgesic, antipyretic and anti-inflammatory actions in different measures. In contrast to morphine they do not depress CNS, do not produce physical dependence, have no abuse liability and are weaker analgesics (except for inflammatory pain). They are also called nonnarcotic, nonopioid or aspirin like analgesics. They act primarily on peripheral pain mechanisms, but also in the CNS to raise pain threshold. They are more commonly employed and many are over the counter drugs.

Willow bark (Salix alba) had been used for many centuries. Salicylic acid was prepared by hydrolysis of the bitter glycoside obtained from this plant. Sodium salicylate was used for fever and pain in 1875; its great success led to the introduction of acetylsalicylic acid (aspirin) in 1899. Phenacetin and antipyrine were also produced at that time. The next major advance was the development of phenylbutazone in 1949 having anti-inflammatory activity almost comparable to corticosteroids. The term Nonsteroidal Anti-inflammatory Drug (NSAID) was coined to designate such drugs. Indomethacin was introduced in 1963. A host of compounds heralded by the propionic acid derivative ibuprofen have been added since then and cyclooxygenase (COX) inhibition is recognised to be their most important mechanism of action. Recently some selective COX2 inhibitors (celecoxib, etc.) have been added.

The antipyretic-analgesics are chemically diverse, but most are organic acids.

CLASSIFICATION

A. Nonselective COX inhibitors (traditional NSAIDs)

1.     Salicylates: Aspirin.

2.     Propionic acid derivatives: Ibuprofen, Naproxen, Ketoprofen, Flurbiprofen.

3.     Anthranilic acid derivative: Mephenamic acid.

4.     Arylacetic acid derivatives: Diclofenac, Aceclofenac.

5.     Oxicam derivatives: Piroxicam, Tenoxicam.

6.     Pyrrolopyrrole derivative: Ketorolac.

7.     Indole derivative: Indomethacin.

8.     Pyrazolone derivatives: Phenylbutazone, Oxyphenbutazone.

B. Preferential COX2 inhibitors

Nimesulide, Meloxicam, Nabumetone.

C. Selective COX2 inhibitors

Celecoxib, Etoricoxib, Parecoxib.

D. Analgesic antipyretics with poor anti-inflammatory action

1. Paraaminophenol derivative: Paracetamol (Acetaminophen).

2. Pyrazolone derivatives: Metamizol (Dipyrone), Propiphenazone.

3.     Benzoxazocine derivative: Nefopam.