While both formulations — for daily use and as needed — of Cialis are generally safe, they may not be suitable for some patients, particularly those with certain underlying health conditions and those who are taking drugs that are incompatible with Cialis.
Men with heart conditions should consult their cardiologist before using Cialis. Doctors may advise against sexual activity for those with advanced heart disease. And those who are taking nitrate-based drugs to treat angina should never take Cialis at the same, because in combination the two drugs can cause a precipitous drop in blood pressure that might even result in death.
Most Cialis side effects are mild and tend to go away after continued use. These include diarrhea, facial flushing, flu-like symptoms, indigestion, and nausea. Patients who experience an erection that lasts for four hours or more or have a temporary loss of vision or hearing after Cialis use should immediately consult a medical professional.