Thanks a lot for your help, he had 25 days of the antibiotic and the Vet stop giving him cause of to much acid in his stomach. He also changed his food to science diet gastrointestinal health. So will ser how it goes.!
I will keep in touch, regards.
By the way, that would apply to many medications, so don't give him Tums if he is on some other medication either, without advice from a vet.
Doxycycline nearly always causes nausea in dogs, and often vomiting. However, it is a very effective antibiotic.
Has he finished the antibiotic course already?
If so, then it would be a good idea if you can feed him some natural "Live" yogurt (unflavoured) daily for a few days until you see any improvement, as this will act as a pro-biotic, replacing natural gut bacteria which will have been wiped out by the long antibiotic course. This will help his digestive balance.
Doxycycline also has a high ph. That means it is very acidic. IF he has finished the course -and only if - then it would do no harm to give him Tums. (plain unflavoured ) A tiny dog like he is would need small amounts, not even a whole Tums tablet, maybe a quarter tablet, and don't overdo it or you could upset his blood calcium balance. If his stomach problems ease then you could stop giving him the Tums.This will help if there is any hyperacidity in his stomach. Tums are pure calcium carbonate. I wouldn't use any other "human" indigestion remedies, as they contain other things which may be harmful to dogs.
If he has not yet completed the course of antibiotics, then it's not so simple, as remedies like this "bind" the medication and can stop it working.