Nyquil
From SNPedia
NyQuil is the brand name for a group of cold medicines; they typically contain analgesics (acetaminophen), antihistamines (Doxylamine succinate), and cough suppressants (dextromethorphan).
SNPs in genes that encode proteins that metabolize these drugs may influence how a person responds to products like NyQuil.
For example, SNPs in the CYP2D6 gene affect the metabolism of dextromorphan.