Google and read all about it. I cut and pasted some of what they listed.

Multaq may increase your risk of heart failure or worsen your heart failure.
Liver damage, also called hepatotoxicity, can happen when taking Multaq.
Lung damage including lung inflammation (also called pneumonitis) and lung scarring (also called pulmonary fibrosis) can happen when taking Multaq.
Multaq may cause a rare dangerous heart rhythm problem called QT prolongation and torsade de pointes. Some people have a higher risk of this, including people who are older, have other people in their family who have had these conditions, have low potassium or magnesium, or who take some medicines for other heart rhythm problems

You are right to question it. And question and investigate on the internet ANY med that is prescribed!!! I will be 76 this month. Congratulations on being 85.