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 |
| Typical price | — | $0.07 /mL | — |
| 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) — the same active combo as Mucinex DM; pick by price. |
Ratings are our independent FDA recall-safety score. General information, not medical advice.
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) — the same active combo as Mucinex DM; pick by price.
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) — note this is the same active combination as Mucinex DM, so choose by price or formulation. 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.