This story is part of CBC Health's Second Opinion, a weekly analysis of health and medical science news emailed to subscribers on Saturday mornings. If you haven't subscribed yet, you can do that by clicking here . Wendy Guimont's tumour didn't kill her.

But a cascade of errors tipped the scales. The beloved piano teacher inspired and trained music instructors for children across Canada. A go-getter who loved to hike, bike and golf, the Cranbrook, B.

C., resident and her husband jumped at the chance to drive an RV to Arizona. While in the U.

S., back pain Guimont had initially brushed off worsened. On Valentine's Day in 2021, she learned she had metastatic pancreatic cancer.

Remarkably, her family says, she gained weight and strength while on chemotherapy. Then, on July 8, 2023, she died — not of cancer, but of kidney failure following a severe drug reaction to the antibiotic vancomycin. "It's just sad because I feel like she could have fought a lot longer and who knows, with my mom, if we didn't have kidney failure to deal with on top of cancer," said daughter Penny Guimont of Grafton, Ont.

, about 120 kiometres east of Toronto. Vancomycin is an antibiotic commonly prescribed to treat infections such as staph. It comes with risks, particularly when the treatment lasts more than a week and in certain patients, such as those aged 65 (such as Wendy), or older.

That's why doctors developed guidelines saying vancomycin levels, when delivered intravenously, need to be carefully mon.