OPIOID PAIN RELIEVERS MAKE HEADLINES

Opioids (morphine-like drugs) are generating a lot of press these days. New versions of these drugs such as Oxycontin® (sustained released oxycodone) have become the drug of choice for many addicts who get a high by grinding the pills and snorting them. The lengths these addicts go in order to get the pills reads like a bad movie script. They masquerade as medical staff, they get prescriptions from multiple doctors, they claim to have lost their pills - they become desperate for a fix.

Yet, opioids are one of the best treatments available for the easing of pain and suffering. They are highly effective for acute pain, and moderately effective for chronic pain. They are remarkably free of any tissue toxicity, which means that they do not harm organs even with long-term use. The main side effects are sedation, constipation, and nausea.

So how did something which has helped thousands of pain sufferers create such a media scare?

The Nature of Addiction

First, let's try to understand the nature of addiction. Addiction is a psychological condition characterized by the inappropriate craving and seeking of opioids for reasons other than the treatment of a medical condition. When opioids are given to patients with addiction problems, their craving increases and their day-to-day functioning deteriorates. Pain patients, on the other hand, will report less pain and their day-to-day functioning will improve.

The media, the general public, patients, and even doctors have always had a difficult time understanding that a person who takes pain medication for a legitimate ailment has an extremely rare chance of ever becoming addicted to pain pills. This has been borne out in study after study. Furthermore, almost all studies of pain treatment reveal that pain is undertreated and that opioids are underutilized, yet many doctors fear providing proper treatment for pain, and a great many people suffer needlessly.

Fear of addiction is what is driving the current media frenzy about these medications. The focus of attention should be on discerning who is an abuser while still making sure that the person with legitimate pain gets the medication necessary for recovery. Monitoring that medication is used as prescribed, and checking for improvement of patient functioning, will help the clinician screen for patients with addiction problems.

Exciting Pain Medication Breakthroughs

Let's take a quick look at the new science underlying the use of opioids. The nervous system functions by the transmission of nerve signals from one nerve cell (neuron) to another. One neuron releases a small amount of chemical (called a neurotransmitter) which fits like a puzzle into the next nerve and activates a receptor. Thus, the pain signal travels from one location to the next until it reaches the brain and causes the sensation of pain. Opioids act like brakes. They activate opioid receptors, which inhibit the neuron, making it is less likely to transmit the pain signal.

There is increasing data that the most effective form of pain management is prevention (see our last Update, March 2001-Preventing Chronic Pain). The newer long-acting or sustained release opioid medications provide steady opioid blood levels, which may help to prevent pain (rather than the more difficult task of trying to catch up after the pain has become severe).

There are several new discoveries about how opioids affect pain signal transmission:

1. It has recently been discovered that some opioids do not only activate opioid receptors, but are also blockers of the NMDA (n-methyl-d-aspartate) receptor. NMDA blockers may actually decrease the development of both chronic pain as well as opioid tolerance.
   
2. Some opioids have been found to inhibit the nervous system's disposal of the neurotransmitters norepinephrine and serotonin. Since these neurotransmitters also act to inhibit pain transmission, this ability may have important analgesic effects.
   
3. Methadone is a particularly interesting opioid because it binds to a recently described sub-type of the opioid receptors, the mu3 receptor. This receptor is found in significant quantities on immune system cells, and may help to diminish pain by decreasing the inflammatory response. (Caution must be used in administering this medication because it's long half-life can lead to accumulating blood levels.)
   

Exciting work is also being carried out on the anti-cancer effects of opioids, specifically methadone and morphine, which appear to induce apoptosis, (a form of cellular suicide) which helps to prevent the growth of human cancer cells and tumors.

The ominous press reports notwithstanding, there is much to be excited about with the new pain medication tools we have!

Until next time...Steven Richeimer, M.D.

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