Using multiple antibiotics for viral common cold is an example of irrational prescribing because antibiotics have no efficacy against viruses. Prescribing multiple antibiotics in this scenario contributes to antibiotic resistance, unnecessary side effects, and increased healthcare costs. Rational prescribing involves using antibiotics only when there is a confirmed bacterial infection, ensuring targeted and effective treatment. Therefore, using antibiotics for a viral illness like the common cold is both clinically inappropriate and potentially harmful.

Reference: Katzung BG, Basic and Clinical Pharmacology, 15th Edition.