Zantac is a really old very well studied anti histamine (H2) that's pretty much free of side effects. It's so safe that 150mg doses were rescheduled from prescription to over the counter medicine about 10 years back. It's has a very simple action that is completely understood unlike many of these dangerous NSAID dog medications where it's hit or miss as to whether your dog could become severely ill. They don't really understand how these drugs work. There's a lot more to it than simply saying it inhibits Cox-2. It's mechanism of action is not understood, nor is the importance of Cox-2 in the blood to mammals.
BUT everything is pretty much understood about Rantidine (Zantac). It can effect the absorption of other medications. But once again it's been used for dogs and humans for so long, there shouldnt' be any suprises. I"M on Zantac, and so is my Lab. Neither of us have problems with it. If you were to search for potential adverse reactions for this drug you'd find a tonne, just like every other medicine. They need to legally protect themselves. but in actual use, it's very well tolerated in dogs.
If you prefer to use non medicines and it's effective than that's still what you should do, just letting you know zantac is a very safe medicine for humans and dogs.