Question

Treatment of disease normally takes a polypharmaceutical approach. That is, different drug classes that have the same end results but have different modes of action are combined and used therapeutically. Using antihypertensive drugs as an example, demonstrate how different drugs, using different modes of action, can lower blood pressure in affected individuals. Your answer should include the drug classes employed, their modes of action to decrease blood pressure and any advantages/disadvantages in their use.

Answer 1

Antihypertensive drugs:

A). Centrally acting drugs: eg- clonidine. Stimulate alpha-2 receptor too much, increases noradrenaline reuptake from synapse. Inhibits sympathetic system activity.

B). Adrenergic receptor blockers: eg- prazosine, trazosine, phenoxybenzamine, phentolamine,etc. Blocks sympathetic action and it relaxes blood vessels. It decreases blood pressure.

C). Directly acting vasodilators: {a} venodilator- eg, Nitroprusside, Isosorbide dinitrate, etc. It act through release of NO. It increases cGMP, cause inhibition of myosin phosphorylation, contraction is inhibited.

{b} arteriolodilator-eg, Hydralazine, Diazoxide, Minoxidil,etc. It acts by increasing K+channel activity, increases hyperpolarization.

D). Ca+2 channel blockers(CCBs): Diltiazam, Verapamil, Nifedipine. It decreases Ca+2 ion influx into smooth muscle of vessels.

E). Angiotensin converting enzyme inhibitors(ACEIs): Captopril, Enalapril, etc. It inhibits ANG II formation that leads to decrease in- blood vessels contraction, blood volume (due to low aldosterone level), sympathetic activation, etc.

F). Angiotensin receptor blockers(ARBs): eg- Losartan, Valsartan, Olmesartan, etc. Act in same mechanism like ACEIs.

Advantages: all the above drug reduce vascular tone, cause vasodilation. The decrease in afterload, makes the heart easy to pump. It all reduces hypertension.

Disadvantages: it may cause low BP, postural hypotension, headache, nausea, vomiting.

Prolong uses of these drugs may cause edema.