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Pathophysiology and Pharmacology

Hypertension is a medical condition that is associated with elevated blood pressure levels. The elevation of the blood pressures results from the increased conversion of angiotensin (i) to angiotensin (ii).this leads to increased vasoconstriction hence increased peripheral resistance. Captopril is a drug of choice in the management of hypertension. Captopril acts by inhibiting the hydralization of angiotensin (i) to angiotensin (ii). Consequently, the lowering of peripheral resistance and blood pressure readings occurs (Henri and rudd, 2007 p. 90).


Hypertension is characterized by the elevation of the blood pressures. Hypertension occurs when the blood pressure reading are above 140/90 for systolic and diastolic readings respectively. Hypertension is broadly classified into primary (essential) or secondary hypertension. The causes of primary hypertension are not associated with an underlying medical condition. However, secondary hypertension is associated with conditions affecting the heart, arteries, kidneys or endocrine system (Schwartz, 2010 p.12).

Hypertension occurs as a result of the increased conversion of angiotensin (i) to angiotensin (ii) by the angiotensin converting enzyme. The hydralization of angiotensin (i) to angiotensin (ii) brings about vasoconstriction. The increased levels of angiotensin (ii) bring about the contraction of the smooth muscles around the blood vessels. The constriction of the smooth muscles decreases the lumen of the blood vessels. Consequently, we have an increase in peripheral resistance. For the body to meet its blood supply demands effectively, the pressure under which blood is pumped from the heart is increased in order to overcome the peripheral resistance. As a result, the blood flows through the blood vessels under high arterial pressures to meet the bodily demands (Atkins, 2011 p. 1586).


Captopril is an angiotensin converting enzyme inhibitor. The angiotensin converting enzyme converts the angiotensin (i) to angiotensin (ii) in blood. The angiotensin 11 is responsible for the the contraction of the muscles around the blood vessels. The narrowing of the blood vessels leads to increased blood pressures. Captopril thus mediates its functions by preventing the conversion of angiotensin (i) to angiotensin (ii). Consequently, the blood vessels relax since the muscles around the blood vessels do not contract. This leads to the dilation of the blood vessels and the lowering of the blood pressures (Mancia, Fagard, Narkiewicz, 2013 p. 1284).



The mode of administration of captopril is through the oral route. The initiation of treatment of hypertension with captopril should be done under close medical supervision. This is attributed to the need to increase the dosage levels based on the patients’ response to the initial dosage. The initial dosage of captopril is 25mg t.i.d. However, if the satisfactory blood pressure levels are not achieved, there will be need to increase the dosage to 50 mg t.i.d. However, if the patient is not responsive, the dosage could be increased up to a maximum of 450mg t.i.d (Mancia, Fagard, Narkiewicz, 2013 p. 1284).


Captopril is metabolized in the liver and converted to active metabolites.


Captopril is highly protein biding. It is distributed in the body when bound to plasma proteins. It however does not penetrate the blood brain barrier (National Institute for Health Care Evidence, 2011 p. 4).


The half-life of captopril is two hours. Captopril is excreted by the kidneys. It is eliminated from the body though urine (National Institute for Health Care Evidence, 2011 p. 4).

Side Effects

The common side effects associated with the use of captopril include persistent dry coughing, angioedema, proteinuria, altered taste sensations, lack of vasoconstriction, bronchospasms and muscle crumps (National Institute for Health Care Evidence, 2011 p. 4).


The use of captopril is contraindicated during pregnancy and should be stopped once pregnancy is detected. Patients with angioedema should also avoid the use captopril. Other conditions in which captopril is contraindicated include renal failure, porphyria and in patients with hypersensitivity reactions to angiotensin converting enzyme inhibitors (National Institute for Health Care Evidence, 2011 p. 4).

Drug Interactions

Drug interactions have been observed when captopril is given with antacids, indomethacin, rifampicin, digoxin, tetracycline and phenothiazine (National Institute for Health Care Evidence, 2011 p. 4).


Atkins GB, et al. (2011). Diagnosis and treatment of hypertension. In V Fuster et al., eds., Hurst’s the Heart, 13th ed., vol. 2, pp. 1585–1605. New York: McGraw-Hill.

Schwartz GL (2010). Hypertension. In EG Nabel, ed., ACP Medicine, section 3, chap. 12. Hamilton, ON: BC Decker.

Henri HC, Rudd P (2007). Hypertension: Context and management. In EJ Topol, ed., Textbook of Cardiovascular Medicine, 3rd ed., pp. 88–108. Philadelphia: Lippincott Williams and Wilkins.

National Institute for Health Care Evidence (2011). CG127. Hypertension: Clinical management of primary hypertension in adults. On-line: NICE Clinical Guidelines.

Mancia G, Fagard R, Narkiewicz K,. (2013). ESH/ESC Guidelines for the management of arterial hypertension. J Hypertens. 2013;31:1281–357.