Pharmacology
Summary
The lesson begins with a review of the role of prostaglandins, a group of physiologically active lipid compounds, in managing smooth muscle contraction. It explains that the proliferation of these compounds is controlled by the enzymes COX-1 and COX-2 which convert arachidonic acid into prostaglandins, thereby mediating the inflammation process. The lesson proceeds to explore how prostaglandins can be pharmacologically administered to impact the smooth muscle of the vasculature, GI, and reproductive tracts. An example given is the use of alprostadil (PGE1), a vasodilator, as a second-line treatment for erectile dysfunction, and to maintain the patency of the fetal ductus arteriosus in certain types of congenital heart disease.
Moreover, the lesson covers the use of misoprostol, a synthetic analog of PGE1, in preventing NSAID-induced peptic ulcers and inducing uterine contractions, while warning of its adverse effects including abdominal discomfort and diarrhea. An overview of dinoprostone, a preparation of prostaglandin E2 is also given, notably its use in inducing abortion, ripening the cervix for labor induction, and promoting uterine contraction. On transitioning to prostaglandin F analogs, the lesson brings up the use of carboprost to increase uterine tone and control post-partum hemorrhage, as well as latanoprost and travoprost in managing glaucoma by increasing aqueous humor outflow and reducing intraocular pressure.
Finally, the lesson delves into drugs used to treat pulmonary hypertension, including prostacyclin agonists like epoprostenol and iloprost, phosphodiesterase inhibitors like sildenafil and tadalafil, and endothelin inhibitors like bosentan. Each of these exert direct vasodilatory effects on the pulmonary vasculature, thereby easing tension and decreasing pulmonary arterial pressure. However, the lesson also highlights the potential risks such as hepatotoxicity and severe hypotension.
Lesson Outline
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FAQs
Prostaglandins and Prostacyclin, both subclasses of eicosanoids, are derived from arachidonic acid in the body. They are integral to various physiological functions. Prostaglandins regulate diverse processes, including smooth muscle activity, blood vessel diameter alterations, blood pressure modulation, and inflammatory responses. Conversely, prostacyclin (or PGI2) primarily functions as a vasodilator and a potent inhibitor of platelet aggregation, vital for maintaining optimal blood flow.
Bosentan, classified as an endothelin receptor antagonist, is prescribed primarily for pulmonary hypertension management. Its mechanism of action revolves around inhibiting endothelin, a naturally occurring vasoconstrictor. By counteracting endothelin's effects, Bosentan facilitates the relaxation and dilation of blood vessels, thereby decreasing pulmonary arterial pressure.
PDE5 inhibitors, which include sildenafil, tadalafil, and vardenafil, are renowned for their role in erectile dysfunction therapy. They exert their effects by selectively inhibiting the enzyme phosphodiesterase-5 (PDE5), accountable for cGMP degradation within the corpus cavernosum. Elevated cGMP concentrations induce smooth muscle relaxation, enhancing penile blood influx during sexual arousal. Beyond this, PDE5 inhibitors find therapeutic application in pulmonary hypertension, aiding in the dilation and relaxation of pulmonary vessels.
Latanoprost, a prostaglandin F2-alpha analogue, is chiefly employed to ameliorate elevated intraocular pressure, making it a therapeutic choice for certain glaucoma variants and ocular hypertension. Its mode of action is attributed to augmenting the aqueous humor outflow from the eyes, culminating in reduced ocular pressure.
