The proper adult dosage of Robitussin Multi-Symptom Cold CF is 10 milliliters every four hours, states Pfizer. The formulation contains an expectorant and cough suppressant to relieve chest congestion and coughing and a decongestant to relieve clogged nasal passages. The night time formula dosage is 20 milliliters every four hours.
The adult dosage for Robitussin DM for cough is 200 to 400 milligrams every four hours, according to Drugs.com. The product may be in capsule, tablet, syrup or oral solution form. The dosage is 600 to 1200 milligrams every 12 hours for extended-release tablets or capsules. It's possible to break the extended release tablet in half if there is a groove in it, but if there is not, the consumer must swallow the whole tablet without chewing, crushing or breaking it.