She is working for Athena following the resignation of director Neil Crump, who has quit to co-found his own agency (PRWeek, 30 September).
Athena MD Cherry Wood said: 'I've known Tessa for many years. She was one of the pioneers to whom we all aspired when we started out in healthcare PR.'
Hopkins has spent the past decade as a director of media training, crisis comms and issues management outfit Lions Den Communications. She will continue in this role, although her
commitments will be scaled back during what will be a six-month secondment to Athena.
Wood is already looking for a full-time replacement for Crump.
Hopkins' PR career began 25 years ago when she joined agency Counsellor. She then spent around four years at B-M before moving to MSD in 1988.
Hopkins met Wood when they worked on the launch of the former Zeneca's migraine drug Zomig eight years ago: Hopkins was freelancing at Hill & Knowlton and Wood was at Zeneca.
Athena clients include Novartis UK and Pfizer UK.