While the media seem embroiled in a moral panic about methamphetamine or “ice”, those of us who actually work with overdose patients are nervously watching out for a far more dangerous drug: carfentanil.
You may have heard of fentanyl, a synthetic opioid similar to morphine, the drug derived from the opium poppy. Fentanyl is 50 to 100 times more potent than morphine, but there wouldn’t be a day that goes by where we don’t use it in the emergency department, mostly for pain relief.
Carfentanil is an ultra-potent synthetic version of this. Its only legitimate use is in veterinary practice for large animals such as elephants. Its distribution is restricted to veterinarians engaged in zoo and exotic animal practice, wildlife management programs, and researchers.
How does it work?
The human body manufactures neuropeptides called endorphins. Opioids work by binding to endorphin receptors in the body, namely opioid receptors.
There are several types of receptors, all which, when activated, create slightly different effects – some make you feel good, or sleepy, or less anxious.
One, called the μ-receptor, is very good at mediating respiratory depression. And carfentanil can activate this receptor better than almost any other opiate.
How was it developed?
Developed in the mid-1970s as a large animal sedative (Wildnil), carfentanil is 10,000 times more potent than morphine. A lethal dose in humans is only 20 micrograms. That is the weight of ten snowflakes, or a single grain of pollen.
It is so potent that lab technicians require special protective equipment to analyse it, and have to have the antidote at the lab bench. It takes only 10mg to knock down a wild African elephant. An unfortunate veterinarian who merely splashed some on his eye while trying to sedate an elk required resuscitation.
What are its uses?
Carfentanil has no therapeutic human application. And for most consumers who have ingested it, they have done so involuntarily, thinking it was another drug, usually heroin.
So why is it available? In the world of heroin, “quality” is frequently conflated with potency. A product that may be significantly “cut” can be dosed with minute quantities of fentanyl-like products to give the impression of enhanced value. By increasing the perceived “purity” of a shipment, you can increase its apparent value.