Final answer:
Pharmacies can transfer controlled substances to another pharmacy without registering as a distributor as long as the transfers do not exceed 5% of the total controlled substances dispensed by the pharmacy in a year.
Step-by-step explanation:
The question pertains to the regulations of transferring controlled substances between pharmacies without necessitating the pharmacy to register as a distributor. According to the United States Drug Enforcement Administration (DEA) regulations, a pharmacy may transfer a controlled substance to another pharmacy without being registered as a distributor provided that the total number of dosage units of all controlled substances transferred does not exceed 5% of all controlled substances dispensed by the transferring pharmacy in a calendar year. If a pharmacy exceeds this threshold, then they are required to register as a distributor with the DEA.