Mondays are the most busiest. MD's coming back from the weekend are able to sign off on requests, hospitals are back in service = more discharges, out-patient clinics & rx's, people who were procrastinating on the weekend pop by after work or on their lunch break
Other trends are days before cold weather or before a blizzard, seniors tend to come and get their rx's early. I always know a storm is coming in a couple of days from the patients who come into the pharmacy LOL (I live in Canada, but pretty sure it's applicable in US too)
Weekends are generally quieter in the area where I work so we catch up on blister packs, call for repeat rx's, do misc. paperwork
(used to work part-time as an assistant for a couple of years)