Although calcium-antagonists can be ,and often are,useful in treatment of hypertension,the most common side-effect is leg swelling (often misinterpreted as sign of cardiac/kidney failure). If the rash does not disappear within 2 weeks,or it reappears within a few days without prednisone,in my opinion,it would be wise to change your antihypertesive to another calcium-antagonist, or some from completely different group of AHT (examples are beta blockers, ACE inhibitors/blockers........). Especially since prolonged use of corticosteroids may cause hypertension! In my experience even a change within the same AHT group can lead to swellings and rash disappearing,and in that manner can contribute to more comfortable and regular use of antihypertensive drug,evenmoreso since it is about prolonged,possibly lifelong use. Best regards!