Can an artery blockage in the kidney be presented by medications for high blood pressure causing a significant drop in pressure?

Yes, in part: Renal artery stenosis can cause reduced flow to the kidney, which perceives this and increases certain hormones to raise blood pressure - causing at times significant jumps in blood pressure that are labile and difficult to control. Certain medicines used to treat routine hypertension can cause dramatic drops in blood pressure. You should have a nephrologist and vascular surgeon involved.