It is co-funded by Breast Cancer Trials Australia NZ, an international trials group that has led many of the region's largest clinical trials.
"We're hoping this trial will provide an affordable, effective means of reducing these side effects," Isaacs said.
The trial's primary target is a complete absence of delayed nausea and vomiting for many patients.
Evangelia Henderson, chief executive at Breast Cancer Foundation NZ, said she was delighted the trial was now recruiting.
"We don't have a lot of multi-centre breast cancer clinical trials in New Zealand, so we see this as a great chance for our hospitals to build their experience in collaborating in this kind of venture."
Patients enrolling in the trial will take either the trial drug, pantoprazole, or a placebo for their first chemo cycle, then will swap around for the second cycle.
Pantoprazole is a type of medicine called a proton-pump inhibitor (PPI), designed to reduce gastric acid.
It was chosen because of its mild side-effects and low likelihood of interaction with other medications, and its high bioavailability (the proportion of the drug that enters the bloodstream to have an active effect).
Find out about eligibility criteria at www.breastcancerfoundation.org.nz/clinical-trials
If you'd like to take part in the trial, talk to your oncologist.