Drug-buying agency Pharmac is urging family doctors to be careful what they say about generic medicines so they don't undermine patients' confidence.
Pharmac often subsidises generic medicines when the regular brand is no longer covered by patent.
Pharmac's 2008 Annual Review, released on Wednesday, said generic medicines have become commonplace, are carefully regulated and their use saves many millions of dollars.
The review said changes to a brand name, or the colour or shape of a tablet can raise understandable questions in a patient's mind.
While health professionals should remain vigilant, it said, they should not undermine patients' confidence unnecessarily.
Pharmac chief executive Matthew Brougham said there will be more such changes in coming months, with switches to generic forms of paracetamol and the heartburn medicine omeprazole.
He said use of generics occurs worldwide, and is one of the key things that enables the purchase of new medicines and new technology.