In A Hospital, Pharmacist's Are On Rotating Schedules, Like Seven Days On Seven Off, Open 7 Days A Week, 24 Hours A Day.

80 Hour Pay Period.

How Is Overtime To Be Calculated With Respects To This 80 Hour Work Week For Their Special Instance

Licensed pharmacists meet the criteria for exempt employment under the Professional exemption. If they are treating you as exempt, they don't have to pay you anything over and above your regular weekly salary no matter how many hours you work.
http://www.dol.gov/esa/regs/compliance/whd/fairpay/fs17d_professional.htm

They are being paid as non-exempt employees

Actually there are a couple of pharmacists paid as exempt.
one is scheduled 70 hours, one is 80 hours.

then there are several paid as non-exempt.
and pharmacy techs paid as non- exempt.

Pharmacy techs would probably not qualify under the Professional exemption. Would it be better if all pharmacists were treated one way or the other? Yes. Is it required under law? No.

Here is the exception for nonexempt employees in a hospital setting (biweekly pay period):
http://www.dol.gov/dol/allcfr/ESA/Title_29/Part_778/29CFR778.601.htm