hi
i have an operation in 2 weeks time. which will be cancelled if my blood pressure remains high. doc put me on Lercanidipine 10mg once a day. how long does it take work. its day for and seen no change. worried about having my op cancelled 
last reading was 169/99
Blood pressure medicine from my experience works right away. Sometimes the doctor will add another medicine that works by a different mechanism
A lot of it is probably related to stress and worry over the operation. Same thing happened to me while waiting for an operation and dr increased my dose which didn't help much. Surgeon said she'd only worry if it got over 200. After surgery BP went back to normal and my dose was reduced again.
That's not that high compared to mine and I've had three long surgical procedures.
I was led to believe that your BP drops when you are unconscious or that the Anaesthetist has drugs that he can use to bring it down.
That has also been my experience. The surgeon said the anesthesiologist could bring down my blood pressure if necessary. It was not necessary, but I was reassured by knowing thisl
Calcium channel blockers tend to work fairly quickly but dont reach their maximum effect for about two weeks. It is cutting it fine really. Whenever people start on BP lowering drugs they often need the dose or drug adjusting to get it right and this needs to be done fairly slowly.