Hi. Weight gain is an important side effect of insulin. The BP lowering medication Amlodipine is a calcium channel blocker which is known to cause swelling of the feet and ankle not to the extent of causing rapid weight gain. Rapid weight gain could be due to some underlying problems in the heart, liver or kidneys which need to be properly evaluated by your treating physician. For diabetic patients the best BP lowering medications are either ACE (angiotensin converting enzyme)-inhibitors like Lisinopril or ARBs (angiotensin receptor blockers) like Valsartan which not only control the BP effectively but also prevent the kidney damage (nephropathy) that might occur as a complication of uncontrolled diabetes. Hope these answer your query.