Pharmacology Essay Example

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The table below shows the list of four receptors from different classes with their endogenous agonists and the relevant selective drug antagonist or agonist.


Endogenous agonist

Selective drug agonist or antagonist

Thyroid Hormone Receptor

Thyroid hormone receptor-α

Thyroid hormone

Retinoic Acid Receptor

Retinoic acid receptor-α

Vitamin A and related compounds

Beta 2 Adrenergic Receptor

β₂-adrenergic receptor agonist


Estrogen Receptor

Estrogen receptor-β


Antagonists at receptors for neurotransmitters or hormones are quite often used clinically. The β-adrenoreceptors antagonists help in the production of useful effects. Beta-blockers drugs helps in binding the beta-adrenoreceptors and this will help block the binding of epinephrine and the norepinephrine to the receptors (Lehne, 2013, p.161). This also inhibits the normal sympathetic effects that usually takes place through the receptors. Beta-blockers bind to the beta-adrenoreceptors that are located in cardiac nodal tissue, contracting myocytes and the conducting system. The heart contains some beta 1 and beta 2 adrenoreceptors and they primarily bind norepinephrine produced from the sympathetic adrenergic nerves. They also bind norepinephrine and epinephrine that circulates in the blood. This helps in preventing the normal ligand from binding to the beta-adrenoreceptor by competing for the binding location (Hemmings, 2005, p.414). This is demonstrated in the following diagram; NE means Norepinephrine, Gs means stimulatory protein, AC means adenylyl cyclase, cAMP means dependent protein kinase, SR means sarcoplasmic reticulum

PharmacologyPharmacology 1Pharmacology 2Pharmacology 3Pharmacology 4

Pharmacology 5Pharmacology 6

Pharmacology 7Pharmacology 8

Pharmacology 10Pharmacology 9

Pharmacology 11

ardiac MyocytePharmacology 18Pharmacology 17Pharmacology 16Pharmacology 15Pharmacology 14Pharmacology 13

Pharmacology 12C

Pharmacology 19Pharmacology 20Pharmacology 21

Calcium Ions

In the above diagram, the beta-adrenoreceptors gets coupled to Gs-Proteins, in which case it activates the adenylyl cyclase to form the cAMP from ATP. The increased cAMP then activates the C-AMP dependent protein kinase (PK-A). This will then phosphorylates L-type calcium channels that cause increased calcium entry into the cell. The high calcium entry in the action potential then results into increased release of calcium by sarcoplasmic reticulum in the heart. This increases contractility. On the other hand, Gs protein activation raises the heart rate. More calcium helps in binding the troponin-C that enhances inotropy. PK-A can phosphorylate myosin light chains that supply to the constructive inotropic consequence of beta-adrenoreceptor motivation. As the level of sympathetic tone on the heart, the beta-blockers reduce the sympathetic effects that stimulate the chronotropy, inotropy, lusitropy and dromotropy. Therefore, the beta-blockers cause helps in decreasing heart rate, conduction velocity, relaxation rate and contractility. Such drugs contain greater influences when there is some elevated sympathetic activity (Hemmings, 2005, p.414).

For the case of atenolol, it might not be possible to treat uncomplicated hypertension in the 68 year with moderate asthma and renal impairment. This is because the drug cannot treat a person with asthma. Atenolol is a beta-blocker and it is quite helpful in treating high blood pressure and prevents the heart attack. Treating the 68 year old requires experienced doctor, especially when one is allergic to atenolol. For the case of metoprolol drug, it would be appropriate to treat the 68 year old. This is because the drug is used to treat hypertension. In addition, the medicine is a beta-blocker and it will work by affecting the response to the nerve impulses. The heart will then beat slower and decreases the blood pressure. When the blood pressure lowers, the amount of oxygen and blood raises increases to the heart. For the case of propranolol, it would not be appropriate to treat the 68 year old using such a drug. This is because one should not take such medication if he or she is having asthma. Although propranol is a beta-blocker and treats hypertension (Hemmings, 2005, 415), the drug cannot treat the 68 year old that is suffering from asthma. The drug is sued to prevent or treat heart attack.

List of References:

Boxtel, C. J. V., Santoso, B., & Edwards, I. R. (2008). Drug benefits and risks: international textbook of clinical pharmacology. Amsterdam, Ios Press.

Hemmings, H. C. (2005). Foundations of anesthesia: basic sciences for clinical practice. St. Louis, Mo. ;London, Elsevier Mosby.

Lehne, R. A. (2013). Pharmacology for nursing care. St. Louis, Mo, Elsevier/Saunders.

Roach, S. S., & Lochhaas, T. A. (2005). Pharmacology for health professionals. Philadelphia, Lippincott Williams & Wilkins.