Hi My Father Is 91 And Getting Weaker. He Uses

Hi my father is 91 and getting weaker. he uses a walker to get around. he is on prednisone and levothyoxine for his thyroid (100mg) He is very tired and wore out now, they prescribed him an antidepressant of duloxetine 20mg. and now he wants to give up living. He was on antidepressants before with suicidal tendancies. So now we are not giving this one anymore wondering if it was just the thyroid med that was making him extra tired.... CAN YOU HELP PLEASE?