DNS: On a prescription, Do Not Substitute. If a physician orders a particular drug and writes DNS on the prescription, that tells the pharmacist not to substitute a generic version or any other drug for the prescribed drug. From Healthy Resources 10 Rheumatoid Arthritis SymptomsWhat Is Exocrine Pancreatic Insufficiency?Understanding COVID-19 Testing and Treatment Featured Centers What Are the Best PsA Treatments for You?Understanding Biologics 10 Things People With Depression Wish You Knew Health Solutions From Our Sponsors