Here is a bill I completely missed.
H.R. 3250 was introduced into the United States House of Representatives on July 28, 2015 and is titled "DXM Abuse Prevention Act of 2015". The PDF version of the bill is located here. The sponsor is Rep. Bill Johnson (R-OH).
The aim of this bill is to set a mandatory minimum age requirement for purchase of Dextromethorphan (DXM) at 18 years. No one 17 years of age or younger will be allowed to purchase DXM or DXM-containing products. The only exception to the age requirement is if the purchaser is an active member of the United States military.
On July 31, 2015, the bill was referred to the Energy and Commerce's subcommittee on Health. No further movement on the bill has occurred.