Page 182 - pharma 1 theoretical updated MNU_Neat

Clinical pharmacy 2024/2025 Level 3 Pharm D Pharmacology 1 (PO 502)
Pharmacological effect of

Prostaglandins & Thromboxane & leukotrienes

• Longitudinal muscle is contracted by PGE 2 and PGF 2α
• Circular muscle is contracted strongly by PGF 2α and weakly by PGI 2, and

is relaxed by PGE 2
GIT • PGE 2 inhibit gastric secretion and increase the secretion of the protective
mucin layer that covers gastric mucosa.

• LTB 4: implicated with inflammatory bowel disease, its amount increased
in epithelial cells of colon,

Vascular • TXA 2 and PGF 2α are potent vasoconstrictors.
smooth • PGI 2 (smooth muscle and endothelial) and PGE 2 (endothelial), promote
muscle vasodilation.

• PGI2 is a potent inhibitor of platelet aggregation.
• TXA2 is a powerful inducer of platelet aggregation

Blood and  The net effect on platelets and blood vessels depends on the balance of
platelet these two prostanoids.
• LTB4 is a potent chemoattractant of neutrophiles.

• L T C4 and L T D4 a potent chemoattractant of eosinophiles.

CVS L T S reduce myocardial contractility and coronary blood Flow.
• Respiratory smooth muscle is relaxed by PGE2 and PGI2 and

contracted by PGD2, TXA2, and PGF2α
Respiratory • LTC4 and LTD4 a potent bronchoconstrictor and increase mucus
system secretion (induce asthma).

So, Antileukotriene drugs, such as zileuton (LOX inhibitor), zafirlukast, and

montelukast (leukotriene receptor antagonist), are treatment for asthma.
• Prostaglandins play important roles in maintaining blood pressure and
regulating renal function.
• PGE 2 and PGI 2 maintain renal blood flow and glomerular filtration rate
Renal system
through their local vasodilating effects and increase Na /water excretion.
+
• TXA 2 causes intrarenal vasoconstriction resulting in a decline in renal
function.

• PGE 2 and PGF 2α in early reproductive processes such as ovulation,
luteolysis, and fertilization.
Reproductive • Uterine muscle is contracted by PGF 2α, TXA 2, and low concentrations of
system PGE 2, PGI 2 and high concentrations of PGE 2 cause relaxation.

• PGF 2α, together with oxytocin, is essential for the onset of parturition.

• PGI 2 increase penile erection.

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