PROSTAGLANDINS

Prostaglandins are (local hormone)unsaturated fatty acid derivatives that act on the tissues in which they are synthesized and are rapidly metabolized to inactive products at the site of action.(can we find it in the circulation?)

prostaglandins contains 20 carbons ( These compounds are sometimes referred to as eicosanoids (prostaglandins, thromboxanes, and prostacyclins); “eicosa” refers to the 20 carbon atoms.Synthesis of prostaglandins phospholipase A2 converts phospholipids of cell membranes to arachidonic acid.
Receptor Mechanisms
 
Prostaglandins bind to prostaglandin (PG) receptors on the cell surface.
There are many types of prostaglandins and each on acts on a specific type of PG receptor.
 
Type of prostaglandin Receptor
 
PGD2 DP1, DP2
PGE2 EP1, EP2, EP3, EP4
PGF2? FPA, FPB
PGl2 IP
 
Alprostadil
Alprostadil is a PGE1 that is naturally produced in tissues such as seminal vesicles and cavernous tissues, in the placenta, and in the ductus arteriosus of the fetus.

Uses:
treat erectile dysfunction

keep the ductus arteriosus open in neonates with congenital heart conditions until surgery is possible.

PGE1 maintains the patency of the ductus arteriosus during pregnancy. The ductus closes soon after delivery to allow normal blood circulation between the lungs and the heart. Infusion of the drug maintains the ductus open as it naturally occurs during pregnancy, allowing time until surgical correction is possible.

Lubiprostone is a PGE1 derivative indicated for the treatment of constipation due to :
chronic idiopathic constipation
opioid-induced constipation,
irritable bowel syndrome with constipation.

It stimulates chloride channels in the luminal cells of the intestinal epithelium, thereby increasing intestinal fluid secretion.

Nausea and diarrhea are the most common side effects of lubiprostone
Misoprostol
 
Misoprostol is a PGE1 analog.

Misoprostol : used for:
1- Gastric ulcer: This drug:
Reduces gastric acid secretion.
Stimulates mucus and bicarbonate production.

This combination of effects decreases the incidence of gastric ulcers caused by NSAIDs.

Prostaglandin F2? analogs
PGF2? analogs include:
Bimatoprost,
latanoprost,
tafluprost,
travoprost
Prostaglandin F2? analogs are used for the treatment of open-angle glaucoma. By
binding to prostaglandin receptors, they increase uveoscleral outflow, reducing intraocular pressure. Epoprostenol , the pharmaceutical form of naturally occurring prostacyclin.
The synthetic analogs of prostacyclin (iloprost and treprostinil ) are potent pulmonary vasodilators that are used for the treatment of pulmonary arterial hypertension.Dizziness, headache, flushing, and fainting are the most common adverse effects
Bronchospasm and cough can also occur after inhalation of iloprost.