When do you use the plural of "medicine"?

Or in other words, I am asking: How do you "count" medicine? Is the word "medicine" like "gas" where a collection of gas is still called gas:

The air was filled with nitrogen gas.

Instead of:

The air was filled with nitrogen gases.

And only in terms of types of gases do you use the plural:

There are many types of gases in the atmosphere.

So, in the following example:

He gave him some medicines.

Does that mean he gave him different types of medicine, or different amounts?

Your answer is different types of medicine.

"I hate this medicine." <- The quantity of specific medicine is unknown, but is typically implied to be one medicine with an unknown amount of doses with only this much context.

"These medicines can all lead to heart failure." <- Unknown quantity per type, but multiple types.

edit: American English speaker, here. I don't know if it's a regional thing, but I typically would hear/read, "They gave him some meds," or "They prescribed him several medications."

I don't think I've heard people say medicines in the sentence you shared.