No interactions. Although grapefruit does have interactions with some drugs it does not appear that mail is one of them.
Yes. They are both ace inhibitors so they can be substituted as long as the doses are adjusted.
Possible multiple. Mavik (trandolapril) is an angiotensin converting enzyme inhibitor, or " ACE". This is a very commonly used class of blood pressure lowering medication. Any blood pressure medication, if too strong, can make you feel weak or light headed, if the reduction in BP is too great. A side effect specific to ACE inhibitors is chronic cough.
Check. Most times the pharmacist can print out a detailed list of side effect. Side effect can vary from one to another best to get a list and check with your symptoms.