One of four deaths of patients on a new blood-thinning drug was in the South, Centre for Adverse Reactions Monitoring senior medical assessor Dr Ruth Savage said.
However, Dr Savage said it was found dabigatran, marketed as Pradaxa, was not a factor in any of the deaths.
Dr Savage declined to specify whether the southern case was in Otago or Southland, citing patient privacy.
Health authorities are keeping a close eye on the anticoagulant after 56 reported bleeds, and the reported deaths, since the drug was introduced in July as an alternative to warfarin.
University of Otago haematologist Dr Jim Faed, of Dunedin, who is part of a nationwide haematology group monitoring the drug, had no knowledge of the southern death.
From what he knew, there had been few adverse events in the South.
He planned to write a second letter to GPs in Otago and Southland stressing prescribing guidelines, pointing particularly to concerns for the 75-80 age range, and for frail elderly people.
He would also remind GPs the drug was not for patients with kidney problems.
Dr Faed believed there was a case for initial prescribing of the drug to be restricted to specialists, rather than GPs. The situation would be carefully monitored by haematologists, he said.
Another possibility was that recommended dosing amounts might need to be changed or refined to deal with individual patient needs.
The drug was still relatively new on the world scene, and "more subtle points of understanding" were built through observing its use in the community.
Asked if that made patients guinea pigs, Dr Faed said they were not, as the drug had been extensively tested and shown to be safe and effective.
"The world is now moving into expanded use with tens of thousands of people being treated. New experience will come from this process. Some of that experience will come from a clearer understanding of the frequency and nature of adverse effects."
While he did not know how many patients had transferred from warfarin to dabigatran, there had been a significant drop in patients requiring the regular blood tests required for managing warfarin.
Dabigatran, which does not require regular testing, is used to prevent blood clots in the veins after surgery. It is also used to prevent strokes and the formation of blood clots in patients who have an abnormal heart beat.
