It is possible to tag blister packs. The transponder would need to be placed in the box away from the foil side of the blister pack, however, to ensure that it could be read properly.
If an ultrahigh-frequency (UHF) tag were placed next to the foil, the antenna would become detuned and it would thus be difficult to read the tag (this is less of an issue with high-frequency [HF] tags). Nigeria’s National Agency for Food and Drug Administration and Control has approved the use of an RFID system to authenticate pharmaceutical products for combating counterfeiters (see Nigerian Drug Agency Opts for RFID Anticounterfeiting Technology).
Tagging individual pills for anti-counterfeiting measures is more problematic. Eastman Kodak has filed a patent for an ingestible pill (see Kodak’s RFID Moment). And researchers in the University of Florida’s Department of Electrical and Computer Engineering have developed a prototype for an ingestible RFID transponder that can be used on pills (see University Team Sees Ingestible RFID Tag as a Boon to Clinical Trials). But these are aimed more at tracking conformance with drug regimens than at preventing anti-counterfeiting.
The read range of any RFID transponder is related to the size of its antenna, because it uses energy captured by the antenna to transmit a signal back to a reader. So a smaller antenna means a shorter read range. Thus, any transponder small enough to be put into a pill would have a very short read range. This would make it difficult to use for anti-counterfeiting purposes, since you would need to get very close to every pill in order to read its tag and account for that pill.
Most pharmaceutical companies that are using RFID for anti-counterfeiting are tagging bottles and shipments. This information is stored in a secure database. As shipments arrive, the receiver can check the database to ascertain if the serial numbers match. If they do not, it could mean that the legitimate shipment was stolen and replaced by counterfeit drugs.
—Mark Roberti, Founder and Editor, RFID Journal