Review of Pharmacology - 9E (2015)

Autacoids
nary bypass. It can also be used for storage of platelets for transfusion.
Uterus
• PGE 2
and PGF 2α
are powerful uterine stimulants (contractor). Dinoprostone (PGE2)
intravaginally and carboprost (PGF 2α
) intraamniotic injection can be used for inducing
mid trimester abortion. Misoprostol (PGE 1
) along with methotrexate or mifepristone
is used for induction of abortion in first few weeks of pregnancy.
• PGE 2
causes softening of cervix (cervical ripening) during labour. Dinoprostone or
misoprostol intravaginally are employed for cervical ripening during labour.
• Carboprost (PGF 2α
) can be used to control post partum hemorrhage (contraction of uterus
leads to compression of blood vessels resulting in decreased bleeding).
• PGs are responsible for pain during menstruation (dysmenorrhoea) and NSAIDs like
mefenamic acid are useful for relieving this pain.
• Use of misoprostol in pregnancy is associated with moebius synrome (abnormal
development of cranial nerves; most commonly VI and VII).
PGI 2
Inhibits platelet aggregation
whereas TXA 2
is a potent aggregator
of platelets.
Bronchus
GIT
Kidney
• PGI 2
and PGE 2
are bronchodilators and TXA 2
and PGF 2α
are bronchoconstrictor
agents.
• Aerosolized PGE 2
has been used effectively to abort acute attacks of asthma.
• COX inhibitors like aspirin cause more production of LTs (because due to enzyme
inhibition arachidonic acid now produces only LTs). Aspirin can result in precipitation
of asthma attacks because LTs are the main bronchoconstricting mediators in human
asthma.
• PGE 2
and PGI 2
decrease acid secretion and increase mucus production and mucosal
blood flow. All these factors decrease the chances of peptic ulcer. NSAIDs on long
term use can precipitate PUD due to inhibition of PG synthesis.
• Misoprostol is the most specific drug for the treatment of peptic ulcer due to chronic NSAID
use. [Remember, the drug of choice is proton pump inhibitors]
• PGE 2
and PGF 2α
cause diarrhea and colicky pain in the abdomen. These symptoms are
important side effects of these drugs.
• PG seems to play some role in colonic cancer. Regular use of aspirin or celecoxib decreases
the risk of colonic polyps and cancers.
• PGE 2
and PGI 2
cause renal vasodilation, natriuresis and increased water clearance due
to inhibition of the action of ADH. These agents also facilitate renin release.
• Loop diuretics act partly by increasing the stimulation of COX; therefore NSAIDs
attenuate the diuretic action of these drugs.
• Bartter syndrome is characterized by excess PGs leading to hyperreninemia, excess
aldosterone and the resultant hypokalemia and alkalosis. Indomethacin is used for
treatment of this syndrome.
Recently it has been found that
aspirin acetylated COX-2 enzyme
can convert arachidonic
acid to 15-HETE (15-hydroxyeicosatetraenoic
acid). In WBCs,
15-HETE is converted to epilipoxins
(15-epi-LXA 4
or 15-epi
LXB 4
). These are called aspirintriggered
lipoxins and have
powerful bronchoconstrictor
action. This finding can explain
induction of asthma with aspirin
but not by other COX-inhibitors.
?
Misoprostol is the most
specific drug whereas proton
pump inhibitors are drugs
of choice for the treatment of
peptic ulcer due to chronic
NSAID use.
General Autacoids Pharmacology
Male reproductive system
PGE 2
and PGI 2
increases sperm motility and enhances penile erection. Alprostadil can be used
to treat erectile dysfunction.
Eye
PGF 2α
decreases intraocular pressure by increasing the uveoscleral outflow. Latanoprost
(PGF 2α
) is being used as eye drops for glaucoma. Bimatoprost, travaprost and unoprostone are
new prostaglandin analogues for this indication.
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