It's bad to drug your dog.
Jane's dog keeps on barking  and barking so Jane can't get to sleep at night.
Jane wants to get to sleep.
Jane trains the dog not to bark unless there's a problem.
Jane gives the dog some medicine so that it falls asleep.
Jane's dog starts being quiet at night on it's own so Jane can sleep.
It gradually takes more and more medicine to work and eventually Jane gives the dog too much and it dies.