Prostaglandins:

They were named so because of their presumed origin from the prostate gland. Human seminal
fluid is the richest known source, but they are also present in various tissues. The
prostaglandins are synthesized from polyunsaturated fatty acids at their sites of action. PG E2
and PG F2 are the two main prostaglandins. They are released in the body by mechanical,
chemical, and infectious insults.
They play an important role in the development of the inflammatory response in association with
other mediators.
Synthesis of important prostaglndins and leukotriens:

Essential Fatty Acids in the diet
Cell membrane phospholipids

Arachidonic acid
5-Lipooxygenase Cyclooxygenase

Leukotrienes Prostaglandins (PGE2, PGF2, TXA2, PGI2)
Pharmacological Actions:
a. Smooth muscle: most stimulate myometrium and are known to be important in the initiation
and maintenance of labor. Prostaglandin E has bronchodilator action.
b. GIT: they increase intestinal motility. PG E inhibits gastric acid secretion and has
cytoprotective action on the gastroduodenal mucosa. Both PG E and F produce contraction
of the longitudinal muscle of the gut. They also stimulate intestinal fluid secretion, resulting
in diarrhea.
c. CVS: PGE is peripheral vasodilator and powerful natriuretic. PGF constricts arterioles and
veins.
d. Platelets: Thromobxane causes platelet aggregation and vasoconstriction. PG I
(prostacycline) is found in the vascular endothelium and is a potent inhibitor of platelet
aggregation and is a vasodilator.
e. Miscellaneous: Prostaglandins are important in pain generation and perception. PGE and
PGI produce hyperalgesia associated with inflammation. In addition, PG E is a potent
pyrogenic substance.
Natural prostaglandins have no therapeutic application because of short duration of action, but
their derivatives such as carboprost, dinoprostone and misoprostol find clinical application.
Therapeutic uses include cervical ripening and labor induction, control of postpartum
hemorrhage, induction of abortion, and prophylaxis of NSAID-induced peptic ulcers. They are
also finding several other uses more recently such as erectile dysfunction, glaucoma, etc.
Adverse Effects include fever, diarrhea, abdominal cramps, headache, nausea, and vomiting