Only if you inhale it with ozone
That's the problem with these guys who come from websites like psychiatrywithoutdrugs or successfulhealthcoach or ne of the many ozone therapy sites, they want to push their view as being the only viable treatment and they supplement the lack of data with a tirade on the established medical treatments. Sure, you can always find something wrong but it doesn't render it useless and, more important, whatever the shortcomings of orthodox medicines, it doesn't make the alternative therapy better. There have been metformin overdoses just as there are asprin or paracetamol overdoses but the biggest reported side effect is wind.