Codeine for post-operative pain

I want to comment on the recent news stories in Canada regarding the use of codeine for post-operative pain in children.  There have been some recent and some not-so-recent deaths due to codeine and this was picked up by the newspapers.  Here are some links to a few of the stories…

Codeine is what we call a pro-drug…that is, a drug that is inactive until it is metabolized somehow by the body after ingestion.  Codeine happens to be metabolized to morphine by a cytochrome enzyme in the liver.  So codeine is simply the pro-drug form of morphine.

When I was in medical school we were taught that 10-12% of Caucasians didn’t have the enzyme required to metabolize codeine to morphine…in these people codeine won’t provide any pain relief beyond the placebo effect.  There is a subset of all other ethnicities that also lack the enzyme, it’s just less common than in Caucasians.

What they didn’t tell us in medical school, was that a proportion of people have a version of the enzyme that causes ultra-rapid metabolism of codeine to morphine.  These people are at risk of morphine overdose when they take a dose of codeine that would be reasonable for the rest of us.  I first heard about this in residency when a paper came out in one of the top-tier medical journals regarding opioid intoxication and overdose in breastfeeding infants whose mothers had been prescribed codeine for postpartum pain.

The Women’s and Children’s hospitals where I trained stopped using codeine for both kids and postpartum moms after this paper came out…they switched to morphine which can be accurately dosed based on weight.  All the guesswork is taken out when you prescribe morphine instead since it is an active drug and not a prodrug.

There’s a lot of discussion in these newspaper articles about how we need to “get the word out” and “change physician habits”.  I agree, we need to change our prescribing practice and most of the hospitals with large pediatric and maternity case loads and the specialty children’s and maternity hospitals largely already have.

What I think is interesting is that no one has yet mentioned what I think is the main reason why physicians still prescribe codeine even with all its known problems.

Codeine does not require the use of a triplicate pad (or duplicate or however many ‘cates are used in your particular province) while morphine does.  Yep, you can write a ‘script for codeine on a regular pad, or a napkin, or the side of your coffee cup and the patient can take it to the pharmacy.  You can even slap on a preprinted patient label…But a ‘script for morphine requires that you *gasp* fill in the patient information by hand into a special prescription pad just for controlled substances.

You have to order these pads from your provincial college of physicians.  You can’t delegate the prescription writing to an underling (resident, med student etc) either.

Quell horror!  The inconvenience!

I’ve lost count of the number of surgeons that have been unable to prescribe anything other than codeine for routine outpatient surgery because they do not carry that special prescription pad.

If we really wanted to get serious about changing physician practice and decreasing our use of codeine (which I think we should) then one simple change would be all it would take….

make ‘scripts for codeine valid only if written on a triplicate pad just like morphine.



Problem solved.

I think I should run for office….


One comment

  1. miriam · · Reply

    I give a pharm lecture to our trainees and codeine is prominently featured. Not only is it a prodrug, but it requires metabolism by two different enzymes for its expected action. So not only do you worry about fast and slow metabolizers (CYP2D6), but you also worry about CYP3A4 since that enzyme is responsible for metabolizing most of your codeine into crap. And since there are so many competitors and inhibitors of CYP3A4, it amazes me that we don’t have more problems than we do.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s

%d bloggers like this: