Why can someone overdose on a penicillin antibiotic but not on a tetracycline?

Penicillin works by preventing cells from dividing. It does not allow them to synthesize cell wall, and thus when the cells attempt to duplicate, they rupture and end up killing themselves. Because penicillin has such a strong focus on a bacteria’s cell wall, it is far more effective on Gram-positive organisms. When a Gram-positive organism attempts to duplicate itself, it must create more cell wall and split off, the penicillin causes there not to be any new cell wall, and instead of duplicating, the cell will simply rupture, effectively killing it.

Tetracycline works by binding specifically to the 30S ribosome of the bacteria, preventing attachment of the aminoacyl tRNA to the RNA-ribosome complex.

I don't think neither of these would cause overdose problems.

I think it has to do with what Bio-man was heading towards... the 30S ribosome is the bacterial characteristic which luckily we don't have and therefore it wouldn't target our own cells, only the bacteria