For the week of October 27, anyway. Walgreens was radio's number one advertiser according to Media Monitors. The pharmacy chain aired over 45,800 commercials for the week. The Home Depot was second for the second week in a row (44,171). AutoZone came in third (32,518) followed by TrueCar (27,004) and GEICO (25,482). The biggest mover into the Top 10 was PetSmart. Two weeks ago PetSmart was 33rd on the Media Monitors list. Last week the company ran 21,600 commercials to come in 8th on the list.