Novamox 250 is an antibiotic (amoxicillin) and is only effective against bacterial infections. Since common colds and dry coughs are typically caused by viral infections, Novamox will not help unless a doctor has confirmed a secondary bacterial infection. Koufrest PD is formulated to relieve symptoms like cough, congestion, and runny nose, making it appropriate for symptom relief. However, "PD" usually denotes a pediatric formulation. You should not use these medications, especially the antibiotics, without a doctor's direct prescription, as improper antibiotic use can cause side effects and bacterial resistance. Please consult a paediatrician for the correct diagnosis and dosage.