My father has been extremely sick for years. He's had diabetes for years, but never took care of himself. He's extremely weak and unable to walk much. He's been sick for a couple of days now and complains that he's been coughing a lot and now has a sore throat. Is cough medicine okay to give him? I asked him if he wanted Halls to help suppress the sore throat and cough, but he wants a liquid like Robitussin.