Final answer:
Laws vary, but DXM-containing products are often not sold over the counter to individuals under the age of 18 due to potential abuse.
Step-by-step explanation:
Dextromethorphan (DXM)—also known as robo—is a cough suppressant and expectorant found in some over-the-counter (OTC) cold and cough medications. While laws regarding the minimum age for purchasing DXM products can vary by country and state, in several places, legislation has been passed to prevent the sale of DXM-containing products to individuals under a certain age, often under 18, due to its potential for abuse by adolescents and young adults. The most common sources of abused DXM are "extra-strength" cough syrup, which typically contains around 15 milligrams of DXM per teaspoon, and pills and gel capsules, which typically contain 15 milligrams of DXM per pill. These OTC medications that contain DXM may also include other substances such as antihistamines and decongestants.