Hi, Thanks for writing to Health Care Magic, I am Dr Asad Riaz, I have closely read your question and I understand your concerns, I will hereby guide you regarding your health related problem. All drugs can be used to control BP , these all have different mechanism that causing decrease in BP like carvedilol causing slowing of heart rate n contraction of heart mainly , hydrazine causing vessel to dilate while lisinopril cause to Dec factors causes vasoconstriction m also Dec fluid retention which also inc BP .. normally BP shouldn t Dec so rapidly Bcs this can lead to some serious complication like ishchmeic stroke.. Bcs sudden drop in BP n also vasodilation may cause pulmonary congestion which may cause shortness of breath .. if u were patient I would like to stop ur hydralazine n also ask u to monitor BP at home n then optimise ur treatment accordingly I hope this answered your question, if you have more feel free to ask. Regards. Dr.Asad Riaz. General and Family Physician..