Wednesday, October 28, 2020

Requiem for a heavyweight 2.

I don’t do much chronic pain direct patient care anymore but I do still work for one clinic in Northern Alberta.  I got a call from the nurse a couple of weeks ago telling me a former patient’s family doctor was desperate to get in touch with me.  I gave her my cell phone number and littering within 5 minutes he called me.  It seems the former patient who was on oral Demerol for her headaches had been told by her pharmacy that oral Demerol was no longer available and he was wondering what he could prescribe.  I told him any short acting opioid would be okay and it would be a bit of trial and error process.  He asked if I could see her which I did recently.

About two or so years ago we were told that injectable Demerol (meperidine) was temporarily not available and it seems temporarily has became permanent.  It is always interesting when a drug which was so widely used is suddenly no longer available.

I like to use generic names but Demerol is so widely used that I continue to call it Demerol.

Demerol was apparently invented in Nazi Germany during the WW2 when supply lines for opium were cut.  Not even the Nazis wanted their citizens to suffer pain.  Methadone was also invented under the Nazis but never caught on as a routine analgesic although it became popular for treatment of addictions and is occasionally used for chronic pain or palliative care.

By the time I was in medical school, Demerol was the drug of choice for surgical and other acute pains.  My first day in clinical clerkship involved scrubbing on an abdominal hysterectomy back when holding a retractor was still exciting.  Part of my educational experience involved learning to write post-op orders and it was then that I wrote my first order for “Demerol 75-100 mg IM q3-4 hours PRN”.  (Technically clinical clerks couldn’t write narcotic orders but in practice we did.). That was the first of 100s of such orders I wrote during clerkship, internship and general practice.

During emergency rotations of course I learned about the use of Demerol for migraine headaches.  Most doctors covering emergency disdained Demerol but still used it for the migraine patients regular or not.

Oral Demerol was used a lot when I was in general practice.  It was the second line when a more potent narcotic was needed or when the patient was allergic to codeine.  There were of course other more potent narcotics like hydromorphone and oxycodone available but doctors seemed to prefer Demerol.

Like all medical students/interns back then we had no formal teaching in how to manage pain.  We learned by watching when doctors did or what we were told to order.  Kind of like today.

Entering my anaesthesia residency my whole attitude to Demerol changed.  Anaesthesiologists in general had a distaste for Demerol.  Part of that was that anaesthesiologists like to administer drugs intravenously and Demerol given intravenously inevitably knocked the bottom of the blood pressure as I learned after a few times giving it.  Most of us preferred IV morphine or fentanyl in the the OR and IV morphine given by recovery room nurses in small increments.  Once the patient left recovery room, they were back under the surgeon and the IM Demerol.  A few anaesthesiologists preferred Demerol; a paediatric anaesthesiologist gave it IM to all her tonsillectomies.  She claimed it worked better with fewer side effects.   Demerol was also popular as a pre-med back when we gave pre-meds.  A resident I trained with who had had a few surgeries told me how he liked to entertain himself while waiting for surgery by watching things crawling up the wall after his Demerol pre-med.

I never quite figured out why people used Demerol to be quite honest.  Explanations I heard included:

Less sedation.

More sedation (when you wanted sedation)

Less nausea

Less addicting

Morphine is only for cancer patients.

Morphine causes histamine release (true but rarely clinically significant)

I have been administering narcotics for quite a long time now both for acute and chronic pain; orally and intravenous and the one I have learned is that I cannot predict what effects patients will get from any given narcotic nor what side effects they will get.  

Having said that Demerol has a few negatives.  The big one is its active metabolite normeperidine which causes seizures.  I first became aware of this while on the Pain Service at the Centre of Excellence.  We followed all the PCA patients and we used either morphine or Demerol.  Morphine was more common but we had a steady number of Demerol PCAs for morphine “allergies” or in a lot of cases patient/nurse/surgeon preference.  I noticed when patients got up to 400 mg every 4 hours (which is a lot, I know) patients got very twitchy and it was time to get them off the Demerol.

While it is popular to blame Purdue and OxyContin for use of narcotics in chronic pain patients, narcotic use was actually quite common when I started working in the Pain Clinic in 1993.   While most patients were on some type of codeine preparation, a significant number of patients took Demerol usually by mouth but there were a small number who got regular injections in the ER, their doctors’ office or alarmingly a few who injected at home.   And I would say almost 100% of the patients on Demerol were happy with it and did not want to stop.  People often forget that when OxyContin came on the market in 1995, a lot of the patients switched to it were on injectable Demerol.

Oral Demerol has to pass through the liver first so normeperidine levels tend to be higher with oral Demerol and I saw a few seizures in chronic pain patients.  What always amazed me how the patients wanted back on (and usually got) Demerol.  One patient reluctantly came off after her third seizure.

At the same time there were a small number of patients for whom Demerol was really the only thing that worked.   I was at pain meeting in the late 2000s and was sitting a table with a number of our province’s eminent pain specialists.  The conversation turned to Demerol and I asked them if they had seen any patients for whom Demerol was the only thing that worked and every single eminent pain specialist nodded his head.  

One of the advantages of getting older is others seeing how dogma becomes heresy and heresy become dogma, is seeing how drugs that were such as important part of medicine just gradually fade away.  Aldomet and of course Pentothal come to mind.  And now Demerol.