The retailer, which is part of the AS Watson group of companies, had worked solely with Z PR since 2006.
This year was the first time it had reviewed its comms agency needs since then and it is believed to have shortlisted four agencies to compete for the business.
Z's brief includes raising awareness of Superdrug's 50th anniversary in 2014, while Cow has been brought in to back its healthcare offering, which was previously handled by Z.
There are pharmacies in more than 200 of Superdrug's 850 stores in the UK and Ireland and it offers an online prescription service, Superdrug Online Doctor, for treatments that would be embarrassing to request in store, such as erectile dysfunction and morning after pills.
Matt Walburn, marketing director at Superdrug, said the appointment of Cow was intended "to give us a bigger voice in health and reflects the importance we are placing on this area of growth for the business".
Superdrug retains Z PR and briefs Cow PR "to give us a bigger voice in health"
Superdrug has concluded a review of its comms needs by retaining Z PR for corporate and consumer PR but adding Cow PR to its agency line-up with a healthcare brief.
