Strong painkillers hardly worked for me during my painful knee surgery

I’ve never had to give anyone that much sedative,” the anesthesiologist remarked upon waking up from my knee surgery last October.

“I used almost a whole bottle. You kept moving, so I had to give you more and more.’

Though I wasn’t conscious enough to feel discomfort, he clearly assumed I was in danger of feeling pain.

Heavily sedated, anesthetized from the waist down, and incredibly relieved that this long-dreaded surgery was over, I didn’t think much about it at the time.

The sedation was administered after my spinal injection, similar to epidural and is commonly used for knee replacements.

I knew what to expect from my previous knee replacement in 2021. I often had to ask for more Oramorph (oral morphine) after the surgery – and it didn’t help much.

This time it had even less effect. The disgusting-tasting liquid made me nauseous and the day after my second operation I took it at least 12 times, but it had little effect.

I was concerned about the amount I was taking, but my nurses said the amount I had was fine, although probably more than many people take.

When I was discharged two days after the operation, I was in such pain that one of the doctors prescribed morphine tablets to take home for five days.

Stronger than Oramorph, it dulled the pain but made me so sick. I barely ate for two weeks and lost 11 pounds. Friends who know of my ongoing weight struggle said, “Well… every cloud.” But I would rather have held the weight than feel awful.

Over the next month or so I became chronically constipated from all the morphine, had brain fog and life was miserable. At night, after hitting my daily morphine limit, the pain brought me to tears.

When my supply for five days was gone, I felt anxious, miserable and could not sleep. A nurse friend said I was going off morphine. I turned to ibuprofen and acetaminophen, but even though I stuck to the daily dose, it upset my stomach so much that I suffered from debilitating diarrhea for a week, so my GP advised me to stop. In agony, I hardly slept for four weeks.

Three months later, much better, I called a specialist to find out if my experience of poor pain relief was common.

Apparently it is, explains Dr. Vivek Mehta, Pain Medicine Advisor at Barts Health NHS Trust in London: “Some patients lack an enzyme, CYP2D6, that impairs the body’s ability to metabolize painkillers, including some opioids.”

There are private tests for the missing enzyme. Whether you have this enzyme is genetic. “Its absence affects 7-10 percent of the Caucasian population,” says Professor Roger Knaggs, President-elect of the British Pain Society. He says a separate enzyme can affect how morphine is specifically metabolized – problems with that are less common. Some people may have the CYP2D6 enzyme, but “it’s too weak to do the job,” says Dr. mehta But the picture is complicated, explains Professor Knaggs, because ‘at least 200 different genes are involved in how we perceive pain. There is often no general answer as to why people react differently to certain analgesics.’

Another factor is that in some people, the opioid receptors – proteins distributed in nerve cells in the brain, spinal cord, gut and elsewhere – become damaged. These receptors block the electrical impulses that create the sensation of pain from traveling through our nerve cells through the spinal cord to the brain.

Opioids attach to these receptors and block pain messages.

Other people may have fewer such receptors, says Professor Knaggs, adding that environmental factors – like car exhaust – could also damage these receptors. Likewise age, weight, gender, liver and kidney function, smoking and alcohol.

Although the exact cause isn’t clear, says Dr. Mehta that it is important for both you and your doctor to be aware if you have resistance to pain medication so that you can be properly prescribed.

Discovering this can be an agonizing process of trial and error, as former attorney Anna McKay, 67, found.

Anna from London developed “a fear of the dentist” as a child as injections to numb her mouth before fillings never worked. Believing the pain was “just normal,” she spent her 20s avoiding the dentist because she was “too scared of the pain.”

Anna also tried over-the-counter painkillers like acetaminophen and ibuprofen for a toothache, with limited success.

“I’m a firm believer that painkillers don’t work for me,” she says — a view reinforced by the fact that she gave birth to both of her sons without effective pain relief.

After epidural “didn’t do anything” in her first labor, she didn’t bother with pain relief in the second because she believed “pain was normal and drugs didn’t work.”

When it comes to toothache, resistance to the effects of local anesthetics like lidocaine could be due to a genetic defect related to sodium channels, according to a 2005 University College London study.

Sodium channels carry sodium molecules through our nerve cells – the mechanism by which the sensation of pain is transmitted. Local anesthesia usually prevents this process, but in people with the genetic defect, the channels remain open, allowing the pain message to be transmitted.

Our emotional state can also play an important role, says Dr. Dev Srivastava, Specialist in Anaesthesiology and Pain Medicine at Raigmore Hospital in Inverness. “When someone is angry or anxious, they feel more pain, which can make it seem like the painkillers aren’t working. It’s an underestimated problem.”

He says such patients are usually offered a “bouquet of psychological therapies” including cognitive behavioral therapy (CBT).

Resistance to painkillers or analgesics is a new area of ​​interest that is now being studied under the umbrella of pharmacogenomics – the study of how genetics can affect a patient’s response to drugs by identifying relevant genetic variants that affect how certain drugs are metabolized affect.

A 2019 paper from NHS Health England’s Genome Education program states: “Pharmacogenetics have tremendous potential to enable more accurate prescribing for better treatment and less waste.”

In the meantime, knowing that the problem actually exists can be an important start for patients. Mum-of-two Maddy Alexander-Grout, 39, from Southampton, has suffered from painkiller resistance for years and has tried numerous forms of relief but none have worked.

“The morphine [Oramorph] I got nauseous and light-headed when I went into labor the first time, but the pain was the same,” she says.

For her second contraction three years later, she asked for an epidural – “that didn’t work either. Both births were painful.

Maddy realized she had an anesthetic resistance problem when she needed three injections at the dentist five years ago just to get a filling. “It made me think that no anesthetic or pain relief ever works for me.”

When I Dr. Srivastava explained that I needed extra sedation during the surgery, he suggested it was because of my anxiety. I’m not convinced because I wasn’t aware that I was feeling particularly anxious.

“How emotions can affect the effectiveness of analgesics is also something we need to know more about,” he said.

“What we do know is that everyone is different. Some people need less, others more. It depends on how sensitive you are to it. And of course your genetics.”