As temperatures begin to drop, health officials are warning British Columbians not to keep naloxone kits in their cars.

The medication, which can reverse a fentanyl overdose, may not be as effective when it gets cold.

"Lots of people opt to keep their kit in their car so it's handy," said Katie Sokil, a health and wellness advocate at the Living Positive Resource Centre.

"That's not best practice though, just because naloxone is temperature sensitive."

Still work but less effectively

Naloxone that has expired or has been exposed to freezing temperatures is not harmful but may be less effective, according to the Provincial Health Services Authority (PHSA).

"Don't leave naloxone in a car or outside for long periods of time," said the health authority's communication officer in an emailed statement.

It doesn't mean naloxone won't work, though.

"You can still use it in an emergency situation," Sokil said.

"But the user should be aware that it may require more doses to resuscitate somebody or reverse an overdose rather than just the standard."

She said it's not clear how much less effective naloxone is when it's been exposed to colder temperatures and the number of additional doses is dependent on the overdose case.

Different brands of naloxone have different temperature thresholds. The PHSA recommends using kits available from the Take Home Naloxone program.

"If your naloxone is exposed to winter temperatures for extended periods or repeatedly, we advise replacing the ampoules [sealed vials] of naloxone at a Take Home Naloxone site," the health authority said.

Places like the Living Positive Resource Centre in Kelowna, B.C., where Sokil works, and other locations across the province distribute naloxone kits for free. They are also available at pharmacies.

Sokil recommended keeping naloxone in a place with a consistent room temperature, like a purse or backpack.

"We recommend trying to keep it on your person or indoors and away from light and extreme heat or extreme cold," she said.

"In an emergency situation, do use it — just know that it might be less effective."