December 2012 ~ Modawy!

Mechanism of action : All drugs in pharmacology - Part 4

ACE Inhibitors :

( Captopril , Enalopril , Lisinopril .... )

It blocks the enzyme that cleaves angiotensin I to form angiotensin II . Thus , circulating angiotensin II levels are reduced and decreases secretion of aldosterone resulting in decreased sodium and water retention . It also diminishes the rate of bradykinin inactivation.
Angiotensin Receptor Blockers ( ARBs ) :

( Losartan , Valsartan , Candesartan .... )

It competes strongly with angiotensin for angiotensin type I receptors. This leads to complete blockade of angiotensin action.

Levodopa :

It is actively transported into the CNS and is converted to dopamine in the brain. This leads to replenishment of dopamine in the brain.
Carpidopa :

It diminishes the metabolism of levodopa in the GIT and peripheral tissues ,thereby increasing the availability of levodopa in the CNS .

Reversible Anticholinestrase :

(Edrophonium , Physostigmine , Neostigmine ... )

It binds reversibly to the active center of AchE preventing hydrolysis of Ach. This leads to accumulation of Ach at cholinergic nerve endings and thus increase its effect.
Irreversible Anticholinestrase :

( Echothiophate , Organophosphate )

It binds covalently via its phosphate group to the serine-OH group at the active site of AchE. This leads to permanent inactivation of AchE and the enzyme has to be re-synthesized.