Benylin is much like the Robitussin formulas marketed here in the U.S. The main ingredient in Benylin, dextromethorphan, is a cough suppressant, according to several websites I saw. The Robitussin DM formula also includes an expectorant, guaifenesin, which means that when you do cough. it's more productive.
I've taken Robitussin products, and there's no interaction with warfarin. At least, none that I've found or experienced.
BTW, I've stopped using the syrups and have switched to Mucinex, which has the same ingredients as in Robitussin DM but in higher dosage. The formula I buy is a 12-hour tablet. Has worked much better.
Next time you're at the pharmacy you might ask the druggist if Mucinex is marketed in Canada. My doctor has given me the green light for Mucinex.
Don't know how long you've had your cold, but have you contacted your family doctor?
