CP Dec DM and benadryl

We found this medication to be largely ineffective, too mild to have an effect om symptoms. My daughter was diagnosed with strep, and takes Claritin daily for allergy symptoms.On top of the strep, she had a nearly non-stop cough. Prescription stated 1 tsp twice daily. On first night of use, we gave 2 tsp and had zero improvement in symptoms. After two hours, gave another 2 tsp (4 total), and again, had zero improvement in symptoms. Following night, abandoned this med, and used individual meds instead of this combo. Used Benadryl to replace antihist, used much cough suppressant individually, but did used same decongestant slightly higher amount. Also, supplemented with Tylenol. Everyone slept on the second night.