Hi, Definitely, headache along with nausea and dizziness is a known side effect with hydralazine. But your doctor has rightly weaned you from lisinopril, due to its lithium elevating effect, which may cause lithium toxicity, which in turn may be fatal many a times. Also, headache with hydralazine is usually a transient symptom, which becomes less severe or resolves completely on its own, with passage of time. Also, occasionally, you may take Tylenol for relief of your headache, as there is no known interaction between Hydralazine and Tylenol. If still the problem is not resolved, then you may switch over to some other group of anti-hypertensive under guidance of your doctor taking into consideration of benefits vs risks. Moxonidine and amiloride may be some of the options, which may be tried for the desired results. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Satnarain Bansal, General & Family Physician