If Malegra Professional contains sildenafil, certain medicines can interact with it and increase the risk of low blood pressure or excessive sildenafil exposure. People should be particularly cautious with: Nitrates such as nitroglycerin or isosorbide — sildenafil should not be used with these because the combination can cause a dangerous drop in blood pressure. Riociguat — contraindicated because both medicines can lower blood pressure. Alpha-blockers such as tamsulosin or doxazosin — may cause additional blood-pressure lowering; medical supervision and a lower sildenafil starting dose may be needed. Some blood-pressure medicines, including amlodipine — blood pressure can fall further when combined with sildenafil. Strong CYP3A4 inhibitors, including ritonavir, ketoconazole, itraconazole, and some macrolide antibiotics — these can increase sildenafil levels and may require dose adjustment. Other ED medicines containing PDE5 inhibitors — combining them is generally not recommended unless specifically directed by a healthcare professional. Because “Malegra Professional” formulations can vary, check the package for its active ingredients and strength before assessing an interaction.