What Are The Side Effects Of Avelox?

My grandfather is 92 always excellent health he has broncitis and Dr put him on Avelox he experienced side effects after taking it 2 times and he had sever shakings,so Dr told him to stop for two days and start again if he is still coughing. That was yesteday well the shakings have gone away but the cough is worse can i give him Mucinex D that had helped me he is on Blood pressure and diabietes meds