90 Section 2/ Drugs Acting on CNSARYL ACETIC ACID DERIVATIVESDICLOFENAC
It is a NSAID with pronounced antirheu-
matic, antiinflammatory, analgesic and an-
tipyretic properties. Inhibition of prostag-
landin biosynthesis is fundamental mecha-
nism of action. In rheumatic diseases, it leads
to marked relief from pain at rest, pain on
movement, morning stiffness and swelling
of the joints, as well as by an improvement
in function.
In posttraumatic and postoperative in-
flammatory conditions, diclofenac rapidly
relieves both spontaneous pain and pain on
movement and reduces inflammatory swell-
ing and wound oedema.
It also exerts a pronounced analgesic ef-
fect in moderate and severe pain of non-
rheumatic origin.
After the passage of the tablet through
the stomach, it is completely absorbed. Due
to the enteric coating, onset of absorption is
delayed. However, once the absorption sets
in diclofenac is rapidly absorbed.
Diclofenac enters the synovial fluid,
where maximum concentrations are mea-
sured two to four hours after peak plasma
values have been attained.
Adverse effects include nausea, vomit-
ing, epigastric discomfort, skin rash, peptic
ulcer, fluid retention, edema and impair-
ment of hepatic function rarely.
It is used in the treatment of inflamma-
tory and degenerative forms of rheumatism,
rheumatoid arthritis, ankylosing spondyli-
tis, osteoarthritis and spondyloarthritis,
painful syndromes of the vertebral column,
non-articular rheumatism and acute attacks
of gout,
Also used in posttraumatic and postop-
erative pain, inflammation and swelling e.g.
following dental or orthopaedic surgery,
painful and/or inflammatory conditions in
gynaecology e.g. primary dysmenorrhoea or
adnexitis, in severe painful inflammatory
infections of the ear, nose or throat e.g.
pharyngotonsillitis, otitis etc.ACECLOFENAC
It is newer COX-2 inhibitor and is a phe-
nylacetic acid derivative. It also inhibits syn-
thesis of IL-1b and TNF-a, thus inhibiting
PGE 2 production. It is rapidly and com-
pletely absorbed after oral administration,
highly protein bound and bioavailability is
almost 100%. It is metabolized to a major
metabolite 4'-hydroxyaceclofenac.
It is indicated for the relief of pain and
inflammation in osteoarthritis, rheumatoid
arthritis, ankylosing spondylitis and
musculo-skeletal trauma.
Adverse effects include dyspepsia, ab-
dominal pain, nausea and diarrhoea.PARA-AMINOPHENOL DERIVATIVESPARACETAMOL
It is a para-amino phenol derivative, acts on
CNS to produce analgesia and antipyretic
effect. It has negligible antiinflammatory
action peripherally in therapeutic uses. It is
poor inhibitor of PG synthesis in peripheral
tissues, but more active on COX in brain. It
also raises the pain threshold.