The dosage for Delsym 12 Hour Cough Relief for adults and children 12 years and older is 10 milliliters every 12 hours, up to 20 milliliters in 24 hours, states Delsym. Children 6 to under 12 years take 5 milliliters every 12 hours, up to 10 milliliters in 24 hours.
Children 4 years to under 6 years old taking Delsym 12 Hour Cough Relief can take 2.5 milliliters every 12 hours, and not more than 5 milliliters in 24 hours, according to Delsym. Children under age 4 years should not take the medication, according to Delsym. The active ingredient in the medication is dextromethorphan polistirex, which controls cough.