Delsym’s main active ingredient is dextromethorphan, a cough suppressant that works by reducing the urge to cough in your brain rather than treating the source of irritation in your throat or lungs. The classic Delsym 12 Hour formula uses a special extended-release form of this ingredient called dextromethorphan polistirex, which is why it lasts twice as long as most cough syrups. Other Delsym products contain additional active ingredients depending on the symptoms they target.
The Active Ingredient in Delsym 12 Hour
The original Delsym 12 Hour Cough Relief contains only one active ingredient: dextromethorphan polistirex. The “polistirex” part refers to a polymer coating around the dextromethorphan that causes it to release slowly in your body over about 12 hours. This is different from most cough syrups, which use a faster-acting form (dextromethorphan hydrobromide) that wears off in 4 to 6 hours and requires more frequent dosing.
Dextromethorphan itself is one of the most widely used cough suppressants in over-the-counter medications. It signals your brain to dial down the cough reflex, which makes it useful for dry, nonproductive coughs where nothing is coming up. It does not treat the underlying cause of a cough, loosen mucus, or relieve congestion on its own.
What’s in Multi-Symptom Delsym Products
Delsym sells several products beyond the original 12 Hour formula, and these contain different combinations of active ingredients. Delsym Cough Plus Chest Congestion DM, for example, contains two active ingredients per 20 mL dose: 20 mg of dextromethorphan hydrobromide (the faster-acting form) as a cough suppressant, plus 400 mg of guaifenesin as an expectorant. Guaifenesin works by thinning mucus in your airways so it’s easier to cough up, making this version better suited for a wet, productive cough with chest congestion.
The children’s version of Cough Plus Chest Congestion DM has the same two active ingredients at lower concentrations: 5 mg of dextromethorphan hydrobromide and 100 mg of guaifenesin per 5 mL. It does not include adult dosing directions, so it’s formulated specifically for kids.
Inactive Ingredients
The inactive ingredients in Delsym 12 Hour include citric acid, edetate disodium, ethylcellulose, FD&C Yellow No. 6 (the dye that gives the orange liquid its color), flavoring, high fructose corn syrup, methylparaben, partially hydrogenated vegetable oil (from soybean and cottonseed), polyethylene glycol 3350, polysorbate 80, propylene glycol, propylparaben, purified water, sucrose, tragacanth, and xanthan gum.
A few of these are worth flagging depending on your situation:
- High fructose corn syrup and sucrose: Delsym contains two forms of sugar, which means it is not a sugar-free product. If you’re managing diabetes or watching sugar intake, this is something to factor in.
- FD&C Yellow No. 6: This is an artificial dye that some people prefer to avoid, particularly for children. It’s responsible for the orange color.
- Methylparaben and propylparaben: These are preservatives. While considered safe at the levels used in medications, some people choose to avoid parabens.
- Soybean and cottonseed oil: The partially hydrogenated vegetable oils come from these two sources, which matters if you have a soy allergy.
Delsym is alcohol-free, which distinguishes it from some other liquid cough medications that use alcohol as a solvent or preservative.
A Key Interaction to Know About
Because dextromethorphan affects how your brain processes certain chemical signals, it can interact dangerously with antidepressants, particularly SSRIs and MAOIs. When dextromethorphan and an SSRI like escitalopram are taken together, both drugs compete for the same processing pathway in the liver. This can amplify their combined effect on serotonin levels and potentially trigger serotonin syndrome, a serious condition that causes agitation, rapid heart rate, muscle rigidity, and in severe cases, seizures.
This interaction is well-documented in medical case reports, and it’s easy to overlook because people don’t always think of a cough syrup as something that could clash with their prescription medications. If you take any form of antidepressant, check with a pharmacist before reaching for Delsym or any product containing dextromethorphan.
How to Tell Which Delsym You’re Looking At
The Delsym product line can be confusing because the brand name appears on boxes with different formulations. The simplest way to know exactly what you’re getting is to flip the box over and read the “Active Ingredients” section of the Drug Facts label. If it lists only dextromethorphan polistirex, you have the extended-release cough-only formula. If it lists dextromethorphan hydrobromide alongside guaifenesin, you have the shorter-acting version that also loosens mucus. Matching the right product to your symptoms, whether that’s a dry persistent cough or a congested chest, makes a real difference in whether it actually helps.