Brief Answer:
Different mechanism of actions

Detailed Answer:
Dear XXXXXXX

Thanks for your query.

Though both the medications are used for management of high blood pressure, their mechanism of action are different.

1. Atacand (pharmacologically Candesartan cilexetil) is an angiotensin II receptor antagonists, that is, it prevents binding of angiotensin (a vasoconstrictor agent responsible for increasing blood pressure) to its receptor in the blood vessels & prevents vasoconstriction (constriction of blood vessels).
It also gives protection from heart failure.

2. Zanadip (pharmacologically Lercanidipine hydrochloride) is a calcium channel blocker, that is, it reduces intracellular calcium, relaxes the blood vessels, lowers the blood pressure and allows the heart to work more efficiently.

Studies have shown that the efficacy of the medications increases when they are used in combination, instead of using them alone.
It also helps in achieving the desired reduction in blood pressure & maintains the optimum level with minimal side effects.

If any one of the medication is taken in increased dosages, the desired effects will not be achieved.
Moreover, it will increase the side effect profile of the drugs leading to sudden reduction of blood pressure, syncope/loss of consciousness, dizziness, headache, effects on liver & kidney functions, etc.

So, kindly take the medications as advised by your treating Physician.
Wishing you a good health.
Take care.

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