Review of Pharmacology - 9E (2015)

Review of Pharmacology
isomerase and can convert cyclic endoperoxides to PGD 2
, PGE 2
and PGF 2α
. Corticosteroids
inhibit the enzyme phospholipase A 2
by inducing the production of lipocortins (Now known as
annexins). NSAIDs decrease PG and TX production by inhibiting COX.
Actions
Autacoids
CNS
PGE 1
and PGE 2
are pyrogenic and cause fever. NSAIDs act as antipyretic agents by inhibiting
these PGs.
Peripheral Nerve Endings
PGE 2
and PGI 2
sensitize pain receptors to various mediators. NSAIDs act as analgesics by
decreasing the synthesis of PGs.
116
Alprostadil is used to keep
ductus arteriosus patent
before surgery whereas NSAIDs
like aspirin and indomethacin
are used for treatment of. Patent
ductus arteriosus
CVS
• PGE 2
and PGI 2
are vasodilators whereas PGF 2α
and TXA 2
are vasoconstrictor agents.
Epoprostenol (PGI 2
) and treprostinil (longer acting PGI 2
analogue) can be used for the
treatment of pulmonary hypertension.
• PGE 2
increases capillary permeability.
• PGE 2
and PGI 2
keeps ductus arteriosus patent. In some congenital heart diseases (like
transposition of great vessels), it becomes essential to keep ductus arteriosus patent
before surgery. For this indication, alprostadil (PGE 1
) and epoprostenol (PGI 2
) can be
given intravenously. If ductus arteriosus fails to close (patent ductus arteriosus) at
birth, NSAIDs like aspirin and indomethacin are given to close it.
Platelets
• PGI 2
inhibits platelet aggregation whereas TXA 2
is a potent aggregator of platelets. Nonselective
COX inhibitors inhibit the generation of both of these compounds. TXA 2
is synthesized in platelets and its synthesis cannot be resumed, once it is inhibited
by NSAIDs (because platelets lack nuclei) whereas synthesis of PGI 2
resumes after
sometime (endothelial cells can synthesize new COX). Net result of this process is
inhibition of TXA 2
synthesis and platelet anti-aggregation.
• Low dose aspirin can be used as an antiplatelet drug for the prophylaxis of MI and
stroke.
• Epoprostenol (PGI 2
) can be used as an anti-aggregatory drug in dialysis and cardiopulmo-
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