The consumption of this drug can lead to some mild and serious side effects which require you to seek immediate medical intervention to avoid any unfortunate consequences. Though most of the times the side effects are not serious and go away by themselves, do go to your doctor if they last more than a day.
Some common side effects include upset stomach, belching, blurred vision, color blindness, headache, nausea, vomiting, flushed skin on the neck, face and upper arms. Side effects that do not need immediate medical attention include sore muscles, congestion, dry mouth, neck pain.
You should consult with professional if you experience loss of vision or hearing, chest pain or if you have a prolonged erection lasting over 4 hours.