Familiarize yourself with the ingredients before taking the medication to make sure none of them will cause an allergic reaction. If you experience any symptoms associated with allergies such as difficulty breathing, hives, swollen tongue etc., stop using the medication and seek urgent medical help.
Common side effects of taking Vardenafil include: headache, skin rash, flushing, nausea, vomiting, pain in the abdomen, bloating and heartburn. Contact your doctor if any of them persist or become bothersome, or if you experience an erection that lasts longer than four hours.
Additional side effects may include: rapid drop of blood pressure, stuffy nose, back pain, diarrhea, upset stomach, warmth or flushes in the upper body, memory problems and changes in color vision. Consult your medical specialist if they persist.
Note that this list does not include all possible side effects. Other side effects might occur depending on individual health conditions.