The phrase "wrong drug" refers to a medication that is prescribed or administered incorrectly, either by mistake or due to an error in judgment. Full definition
And, unfortunately, picking the wrong drug can lead to treatment failure. (sciencedaily.com)
However, as a result of use and misuse of antibiotics (such as using the wrong drug, or not completing the full course of treatment) bacteria can develop drug resistance (known as acquired drug resistance). (sciencedaily.com)