The Dimetapp dosage by weight for a 12- to 17-pound child is 1/2 teaspoon every six hours, and an 18- to 30-pound child should receive 1 teaspoon every six hours, according to Beverly Hills Pediatrics. For a 31- to 44-pound child, the dosage is 1.5 teaspoons every six hours.
Children 45 pounds and heavier, who typically range in age from about 6 to 12 years old, should receive 2 teaspoons every six hours. Weight-based pediatric medication dosages do not always match age-based dosages, but dosage by weight is the preferred standard of measure, notes Beverly Hills Pediatrics. Pediatricians may recommend that children be at least 4 years old before taking cold and cough medications. Dimetapp is for children who are at least 6 years old, according to Pfizer.