Pharmacology for Dentistry

226 Section 5/ Autacoids

PGE’s & PGI 2 also inhibit gastric acid
secretion stimulated by gastrin or histamine.

Cardiovascular system: PGE’s are
potent vasodilators. However, PGF’s
constricts arterioles and veins. PGI 2 inhibits
the aggregation of human platelets in vitro.
TXA 2 is a very powerful inducer of platelet
aggregation. LTB 4 stimulates the
aggregation of polymorphonuclear
leukocytes.

Endocrine system: Systemic
administration of PGE 2 increases circulating
concentration of ACTH, GH, prolactin &
gonadotrophins.

It has also been observed in experimental
animal that PG’s cause regression of corpus
luteum and reduction in secretion of
progesterone.

Central & peripheral nervous system:
PGE 1 & PGE 2 increase body temperature. They
also contribute importantly to the genesis of
the signs and symptoms of inflammation.
When injected intracerebroventrically, PGE 2
produces sedation, rigidity and increased
body temperature.

Kidney: PGE 2 and PGI 2 increases water,
Na+ and K+ excretion and have a diuretic
effect. Prostaglandins probably modulate

renal blood flow and may serve to regulate

urine formation. It also plays a role in the

regulation of the secretion of renin (PGI 2 ,

PGE 2 & PGD 2 evoke release of renin). PGE 2

and PGI 2 cause renal vasodilatation while

TXA 2 causes renal vasoconstriction.

Uses of Prostaglandins

1. Abortifacient: Intra-amniotic adminis-
   tration of PGF2a produced abortion with
   less severe adverse effects. It is used to
   induce second trimester abortion & usu-
   ally administered as a single 40 mg in-
   traamniotic injection.
   Synthetic PGE 2 analogues are also used
   as suppositories for abortion. It directly
   affects the collagenase of the cervix and
   also stimulates the contraction of the
   uterus.


2. Induction of labour: PG’s do not have
   any advantage over oxytocin for the
   induction of labour. The adverse effects
   of the prostaglandins are slightly higher
   than that produced by oxytocin. PGF2a
   has more gastrointestinal toxicity than
   PGE 2 and is a bronchoconstrictor also.
   Oral PGE 2 is superior to oral oxytocin.
   PGE 2 & PGF2a is used in place of
   oxytocin in renal failure patients.

Table 5.3.1: Classification of prostaglandin analogues.

PGE 1 Misoprostol (CYTOTEC) 200 μg/day oral

Rioprostil

PGE 2 Enprostil

Arbaprostil

Trimoprostil

Dinoprostone (PROSTIN E 2 )

PGI 2 Carbacyclin

Iloprost

PGF 2 α Dinoprost (PROSTIN F 2 ALPHA)