HI, I'm Dr STeve, I'm Sorry to hear about Poochie. From your description, it does sound like he may have had a reaction to Frontline. As a rule Frontline is usually very safe, but as dogs age, they can develop or become more sensitive to things that previously have not bothered them . It is encouraging that he is better at least somewhat today. The medicines you mentioned are antibotics and will not likely do anything for him since it sounds more consistent with an allergic reaction than an infection. I have had clients give benadryl at a dose of 1 mg per pound body weight to dogs with allergic problems. If he is not better by morning you should have him examined. There are 2 reasons to have him looked at in the morning. One is that as a rule most allergic reactions tend to get better in a day or two and since he is not drastically better, he may need some extra help. Secondly, with his age allergic reactions can be more severe and having him checked out can help determine if there is possibly anything else going on in addition to an allergic reaction. If he would happen to get worse through the night, it may be best to take him to a vet at that time if anything would happen. I also would recommend having him sleep near you tonight do you can hear if he would start having any more difficulties during the night. Things to watch or listen for in addition to his current symptoms would be increased breathing rate, or heart rate and labored or difficult breathing. I don't think these will occur , but wanted you to be aware if them just in case. ANother thing that you could do to address Frontline reaction possibility wold be to give him a bath using Dawn dishsoap to help remove as much of the Frontline as possible to prevent any further exposure to the ingredients in Frontline. I hope this has helped. If it has would you please rate my answer. I will check tomorrow to see if you have more questions, Thanns for your question and good luck.