Disclosed is a system for treating hypertension, said system comprising: - a catheter adapted to be introduced to the renal vasculature of a patient - a needle deployable from the catheter to penetrate a wall of a renal vessel into the adventitia or perivascular space surrounding the renal vessel and - a source of guanethidine to be delivered through the needle into the adventitia or perivascular space surrounding the renal vessel to lower the systemic blood pressure of the patient by a therapeutically beneficial amount, wherein the needle is sized and/or orientated to deliver guanethidine into the adventitia or perivascular space surrounding the renal vessel when the aperture of the needle is positioned beyond the external elastic lamina of the renal vessel wall and into the perivascular space surrounding the renal vessel wall.
