Labman there are many disadvantages to putting medication down the toilet or sink.
Here is a previous post I made concerning this.
https://www.askmehelpdesk.com/other-...tml#post854754
Although putting medication in the bin is not ideal it is safer than the waterways were they have a chance to poison the environment, animals and ourselves.
If I had to throw medication in the bin I would put it in a closed container than paws can't open (or break). Another thought would to put something completely unpalatable over the pills. Bleach was my first though- although there might be a strong reaction, it might only be safe to do this if you know your chemistry. EDIT just thought about fumes definitely not a good idea!
I'm sure there must be something somewhere that dogs and cats don't eat. Although on the other hand, I have seen a dog eat a rubber band so I wouldn't put any money on it...