Our ME dogs can sometimes lose their appetites more readily due to aspiration pneumonia, separation anxiety, being nauseated from medications they are taking, or being in a new environment (newly adopted, in a shelter, etc). Make sure you carefully work with your veterinarian to figure out why so if treatment is needed your dog gets started quickly and is on the proper protocol.
If you are afraid of aspiration pneumonia with not eating, Clavamox is not likely your drug of choice, unless you are certain that he isn’t affected by it. Most animals get a bit urpy or nauseated from it. Use Baytril instead, much less likely to upset the stomach! Just know that Clavamox can make a lot of dogs (not all) nauseated. So, if you do start it that may complicate diagnosing why he isn’t eating, however, it is never unwise to start antibiotics w/ loss of appetite. Cerenia orally or by injection (your dvm can teach you how) can be given.
For some dogs, adding a dosage of hydroxyzine to their regime, once a day, usually makes them hungry. Why, we aren’t sure, but it is harmless and works more often than not. You can wean them after several days if you want. Check with your veterinarian, as always. It is a prescription item, anyway.
More importantly, you need to know that there are other reasons why a dog might have loss of appetite and interest in eating. Some are not important, unless it lasts. Some are very important and require treatment promptly. Not everything that affects our dogs with megaesophagus is related to it!
NOTE TO ALL: PUTTING CERENIA INJECTABLE IN THE FRIDGE MAKES IT STING LESS!!!