My Husband Has Been Subscribed Cialis For ED. He Had

my husband has been subscribed Cialis for ED. He had taken viagra with heart palpitations in the past with out results. He is concern about those side effects with taking the Cialis, also, he is unsure of the daily dosage and how long after the first dose do you see affects ?
Please advise , the sooner the better....
thank you,
desperate and Horney