BATON ROUGE - While in the wrong hands, fentanyl can cause fatal overdoses, it has legitimate and necessary medical applications.

Used as a pain management tool by doctors and paramedics, the highly requested drug is on a nationwide back order.

"We were notified by our supplier not long ago that there was a shortage and it would be on back order. We bought what we could and stocked as much as we could, but we are out. We've been out for about three weeks," Mike Chustz with East Baton Rouge EMS said.

Now paramedics are having to use other drugs to help patients.

"In most cases fentanyl would be the desired medication, but we just use what we have."

One option they've been using is ketamine.

"Works really, really well for pain. Probably works as good. Just some of the additional behaviors of that medication are different from fentanyl. In some applications you prefer using fentanyl over ketamine."

However, not all meds are interchangeable. During a shortage in 2010, a mix up between morphine and hydromorphone caused two deaths.

But Chustz says so far, they haven't had any complications.

"We haven't noticed any negative side effects with any of our patients that we've noticed or that have been brought to our attention and we're hoping to keep it that way. Hopefully we can get a new shipment in the next week or so."

The supplier says more fentanyl should be available by the end of the month.