Antihypertensive Drugs

Hypertension (HTN) or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. It is the opposite of hypotension. Hypertension is classified as either primary (essential) hypertension or secondary hypertension; About 90–95% of cases are categorized as "primary hypertension," which means high blood pressure with no obvious medical cause.  The remaining 5–10% of cases (Secondary hypertension) are caused by other conditions that affect the kidneys, arteries, heart or endocrine system.

Classification	Systolic pressure		Diastolic pressure
	mmHg	kPa	mmHg	kPa
Normal	90–119	12–15.9	60–79	8.0–10.5
Prehypertension	120–139	16.0–18.5	80–89	10.7–11.9
Stage 1	140–159	18.7–21.2	90–99	12.0–13.2
Stage 2	≥160	≥21.3	≥100	≥13.3
Isolated systolic hypertension	≥140	≥18.7	<90	<12.0

 drug Rx  include reduction  in blood  volume,  reduction in sympathetic  tone, reduction in vagal tone, and relaxation of vascular smooth muscle. Note that depending on the anti-HTN drug used, homeostatic mechanisms may lead to compensatory responses of salt and water retention and/or reflex tachycardia.

Table . Classes of Drugs Used Categorized by Blood Pressure Determinant Affected 



SYMPATHOPLEGICS 

Drugs Acting in the CNS
 
Methyldopa

Pro-drug  converted  to  a-methyl-NE, which  activates presynaptic  a2  adrenoceptors in  the
medulla to decrease  vasomotor  outflow, mainly lowers  PVR. Used  in  mild-to-moderate  HTN.
Decreases left ventricular  (LV) hypertrophy.
Adverse effects: sedation, dizziness, decreased libido, edema, positive Coombs' (hemolysis).
Safe in renal dysfunction and in pregnancy.


                               Fig: The Angiotensin System



Table:  Use of Antihypertensive Drugs in Cornorbid Conditions



Table: Summary of the Types and Properties of Antihypertensive Drugs