Amlong and S-Numlo are merely brand names. Both contain the same medicine i.e. amlodipine. There is no scientific rationale for replacing one brand with just another brand. You were prescribed two medicines: amlodpine and losartan. Since your blood pressure is controlled just with one medicine i.e. amlodipine, you can continue to take the same (Amlodac from Cadila is the most economical brand) 5mg in the morning daily. Even when the BP is well controlled sometimes there can be temporary fluctuations due to life style reasons such as stress, salt intake etc. One must not jump to additional medicines unless it is established that one drug is not adequate over several weeks. More drugs will mean more side effects.