It is possible. Cimetidine has recently been found to have anti-cancer actions. It is also an H2 blocker, meaning it blocks histamine 2 receptors.

Cimetidine also has dramatic effects on the metabolism of drugs in the liver. It can cause other drugs to be metabolized more slowly when cimetidine is present.

https://livertox.nih.gov/Cimetidine.htm

If you go to drugs.com and use their drug checker you can put in all the drugs and supplements you use to see if cimetidine interacts metabolically with them.

Dogs share some biological traits with humans, but they are not 100% like us. Some things may work for them, and not us.

I would not try cimetidine without medical supervision because of your medical situation. It is available in 200 mg doses OTC in stores. On RX the doses are stronger, up to 800mg each.

Cimetidine as an H2 blocker is used in treating some allergic states, and also to prevent allergic reactions to imaging dyes during tests like MRIs, etc. It is used with prednisone and Benadryl for this purpose.