Depending on the medicine, some are not only useless but actually harmful.
Literal
Medicine [depending-on-によっては], useful [far-from-どころか] conversely harm become-things [also-も] exist.
Three instructive patterns stacked: ~によっては ('depending on X' / 'for some X') sets up the conditional; ~どころか ('far from X, even Y') reverses the expected expectation; and ~ものもある ('there are also things/ones that...') is a common way to pick out a subset. 逆に ('conversely') reinforces the contrast. A strong example of layered contrastive grammar.