Drinking a large amount of cough medication is a common method of abusing which drug?

The correct choice is codeine. Cough medications often contain codeine, which is an opioid effective for treating cough. When consumed in large quantities, individuals may seek the euphoric effects that can accompany codeine, making it a target for misuse. Codeine can be found in many prescription cough syrups, and abusing these formulations can lead to dangerous side effects, including respiratory depression and addiction.

Hydrocodone, oxycodone, and morphine are other opioids but are typically found in different medications or formulations. Hydrocodone is often prescribed for pain relief but is less commonly found in cough syrups than codeine. Oxycodone is also primarily used for pain management and is not typically associated with cough medications. Morphine is a strong opioid pain reliever and is rarely found in over-the-counter cough medications, making it less relevant in this context. Thus, codeine stands out as the drug commonly abused through the misuse of cough syrup containing it.