The most common OTC drugs to be misused, and potentially cause dependency, are those containing the opiate codeine , a painkiller used to treat moderate pain, such as headaches or dental pain. In its purest form, codeine is only available on prescription but when mixed with aspirin, ibuprofen or paracetamol, it's available for anyone to buy over the counter, in Boots, any pharmacy or at your local supermarket. The guidelines around sales of codeine-based painkillers were tightened in 2009 to help combat overuse and misuse. Warnings about the importance of sticking to the recommended dosage and the drug's addictive properties were added to packs – the label for Nurofen Plus , for example, clearly states that codeine can "cause addiction if you take it continuously for more than three days".