API limit?

[saschatts]

I am attempting to pull data at the county level for all counties in the US for three specific drugs included in the dataset, in order to do this I was hoping to simply loop through the county list (~3000+ counties) and retrieve data for the three specific drugs (using drug_county_biz()). After Prowers, CO (291 counties in) I am no longer able to retrieve any data, all are returning "500 - Internal server error". Is there a limit on the number of API calls and if so is there any way to bypass this?