Delsym vs Mucinex vs Robitussin DM: which cough medicine should you use?
These three cover the three kinds of cough medicine. Delsym is a long-acting cough suppressant, Mucinex is an expectorant that loosens chest mucus, and Robitussin DM combines both. The right one depends on whether your cough is dry or chesty.
Match the medicine to the cough. For a dry, hacking cough, a suppressant like Delsym (dextromethorphan) quiets the cough reflex — and it lasts about 12 hours. For a wet, chesty cough, an expectorant like Mucinex (guaifenesin) thins and loosens the mucus so you can clear it. Robitussin DM puts a suppressant and an expectorant together for a cough that comes with chest congestion. It's usually a mistake to suppress a productive cough you need to clear.
| Delsym dextromethorphan | Mucinex guaifenesin | Robitussin DM dextromethorphan + guaifenesin | |
|---|---|---|---|
| Active ingredient | Dextromethorphan Polistirex | Guaifenesin | Dextromethorphan and Guaifenesin |
| Our rating | Not yet rated | Not yet rated | Not yet rated |
| Pharmacy pays | No data | $0.07 /mL | No data |
| Cough it suits | Dry, hacking cough | Wet, chesty cough with thick mucus | Cough with chest congestion (both) |
| How it works | Dextromethorphan suppresses the cough reflex | Guaifenesin (expectorant) thins and loosens mucus | Suppressant (DXM) + expectorant (guaifenesin) |
| Dosing | Long-acting — about every 12 hours | Extended-release, about every 12 hours | Shorter-acting — about every 4 hours |
| Good to know | A pure suppressant — quiets a dry cough but doesn't loosen mucus. Handy 12-hour dosing, good overnight. | Loosens mucus rather than stopping the cough; pair with fluids. Doesn't suppress the cough. | Two-in-one (suppressant + expectorant) — same actives as Mucinex DM, but dosed about every 4 hours vs Mucinex DM's 12-hour extended-release. |
Ratings are our independent FDA recall-safety score. General information, not medical advice.
Which should you choose?
Delsym (dextromethorphan)
A pure suppressant — quiets a dry cough but doesn't loosen mucus. Handy 12-hour dosing, good overnight.
Mucinex (guaifenesin)
Loosens mucus rather than stopping the cough; pair with fluids. Doesn't suppress the cough.
Robitussin DM (dextromethorphan + guaifenesin)
Two-in-one (suppressant + expectorant) — same actives as Mucinex DM, but dosed about every 4 hours vs Mucinex DM's 12-hour extended-release.
Pick by cough type. Dry/tickly cough → a suppressant; Delsym is convenient at roughly 12 hours a dose. Wet/chesty cough with phlegm → an expectorant (Mucinex) plus plenty of fluids; don't suppress a cough that's clearing mucus. Cough with both → Robitussin DM (dextromethorphan + guaifenesin) — the same active pair as Mucinex DM, though Mucinex DM is a 12-hour extended-release tablet and Robitussin DM is a liquid dosed about every 4 hours, so match the dosing schedule you want, not just price. A few cautions: dextromethorphan (in Delsym and Robitussin DM) shouldn't be combined with MAOI antidepressants or misused at high doses; drink water with guaifenesin. See a doctor for a cough lasting more than about three weeks, or with high fever, coughing up blood, or trouble breathing. General information, not medical advice.
Frequently asked questions
Should I use a suppressant or an expectorant for my cough?
Use a suppressant (Delsym, dextromethorphan) for a dry, hacking cough that's just irritating; use an expectorant (Mucinex, guaifenesin) for a wet, chesty cough so the mucus loosens and clears. Robitussin DM combines both for a cough with congestion. Generally, don't suppress a productive cough you need to clear.
Is Robitussin DM the same as Mucinex DM?
They share the same two active ingredients — dextromethorphan (a cough suppressant) and guaifenesin (an expectorant) — but the formulations differ: Mucinex DM is a 12-hour extended-release tablet, while Robitussin DM is a liquid dosed about every 4 hours. Pick by the dosing you want (all-day cover vs shorter-acting), not just price.
How is Delsym different from regular cough syrup?
Delsym uses an extended-release form of dextromethorphan, so one dose lasts about 12 hours instead of every 4 hours — convenient for all-day or overnight relief. It's a suppressant only and does not loosen mucus.
Can you take Delsym or Robitussin DM with cold medicine?
Watch for duplicate ingredients — many cold products (e.g., DayQuil/NyQuil) already contain dextromethorphan, and you shouldn't double up. Combining can also add acetaminophen from a cold combo. Check labels and ask a pharmacist before stacking.