Medicines safety regulator Medsafe says it will fast-track applications which have been made to supply alternative brands of the drug Thyroxine.
A spokesperson for Medsafe, Stewart Jessamine, says more than 800 people have reported adverse reactions to Eltroxin - the only brand of the medication licensed in New Zealand for treating hypothyroidism, also known as an under-active thyroid gland.
The company which makes the drug, GlaxoSmithKline, changed the formula used to make it in the middle of 2007, and no longer supplies it in its previous form.
Dr Jessamine says two applications have been submitted from companies which can supply alternative drugs.
He says he expects patients to have access to the drug in October.