The most common side effects are headaches, feeling sick, indigestion and dizziness. If you understand the reasons why most online pharmacies are not safe or legal, then you’ll better understand how to make a wise choice. Yes, ED pills can cause side effects. Rarely reported side effects include: an erection that will not go away priapism. You should also call your insurance company to see if they cover erectile dysfunction medications. Follow-up support: Make sure you can get the help you need if questions or concerns arise after ordering.Yes, it can be legal as long as certain rules are followed. Whether or not it is legal to purchase your prescription drugs online depends on various factors: your location, the .  · a light-headed feeling, like you might pass out. Common sildenafil side effects may include: flushing (warmth, redness, or tingly feeling); headache, dizziness; heartburn, nausea, or upset stomach. abnormal vision (blurred vision, changes in color vision) runny or stuffy nose, nosebleeds; sleep problems (insomnia); or. Men will no longer require a prescription to obtain the impotence drug Viagra and will instead be able to buy it over the counter at pharmacies.