Zenegra 50 mg should be taken about 30 minutes to 1 hour before anticipated sexual activity. It’s important to note that the medication does not automatically cause an erection; sexual stimulation is still necessary for it to work effectively. Common side effects of Zenegra 50 mg may include headache, flushing, indigestion, nasal congestion, dizziness, and vision changes. These side effects are usually mild and temporary.