Med route error?

We have an Ativan protocal that my floor is to follow for acute alcohol withdrawal. The route and dose depends on the patients score. Throughout the night my pt scored a 10 - 14 and Ativan was IVP 4-6mg (should have been on a drip, but they wouldn't authorize a transfer to ICU); later in my shift patient scored 8, Ativan 2mg. The protocol sheet called for an IM or PO route not IVP. I chose IM because pt was not cooperative with PO route. Later when I was reviewing my meds, the doc had written out IVP as the route. The protocal sheet for our floor called for PO, IM, IVP depending on the score. Did I make a med error? I will ask the supervisor also. I just feel awful.