We remind you that if your erection lasts 4 hours or longer, you should seek medical advice immediately. Although this is rare, you should seek medical advice immediately to avoid permanent damage.
Also, you should not take a combination of several erectile dysfunction medications. There should be a break of 24 hours between 2 doses (36 hours for Cialis/Tadalafil) to avoid risks. Also, you should not exceed the prescribed dose.
Be aware that it is recommended to have already had experience with Sildenafil or Tadalafil or Viagra or Cialis before trying different strengths.