It is hard to tell whether reports of adverse reactions for thyroid drug Eltroxin received by the Centre for Adverse Reactions Monitoring in Dunedin have reached a plateau or if they are the tip of the iceberg, centre director Dr Michael Tatley says.
The centre has received about 200 reports in recent weeks following publicity over the drug, which is used by about 70,000 people in New Zealand to treat under-active thyroid glands.
Patients who have gone public with their concerns have suspected a wide range of side effects, including nausea, sore eyes and weight gain, and some have been worried their normal doses were proving ineffective, returning them to their pre-medicated condition.
The drug is manufactured by GlaxoSmithKline and is the only brand of thyroxine tablet to be publicly funded.
Last July, the base formulation of the drug was changed, and manufacture moved from Canada to Germany, but the active ingredient, thyroxine (or levothyroxine), remained the same.
Patients with concerns have been advised to contact their doctors and arrange blood tests, to check their thyroid activity.
Dr Tatley said where doses were found to need adjustment, the results were not instant and it could take some weeks to get the levels correct and for symptoms to abate.
Last week, Medsafe advised it was considering the possibility there was a problem with the current batch of the drug, and that it was retesting the drug.
It also advised that it was working with GlaxoSmithKline to see if a different formulation could be made available.
