You can give Codeine or Tramadol, which are opiates that produce no "high" when taken in standard therapeutic doses. People do abuse them by taking a whole box

You can give Codeine or Tramadol, which are opiates that produce no "high" when taken in standard therapeutic doses. People do abuse them by taking a whole box at once, but you won't end up in a scenario like in OP's story where someone discovers it "solves all their problems" after receiving them for moderate pain from a routine medical procedure, and has them shooting heroin 6 months later.