Physician Concerns Regarding Prescribing Opiates for Chronic Pain
Opiate medications are highly effective in the control of pain. However, physician comfort level in prescribing opiate drugs for the treatment of chronic pain varies with patient characteristics, according to a recently published survey.
Researchers at the University of Wisconsin and the Medical College of Wisconsin analyzed questionnaire responses from 248 primary care physicians. Results showed that the most common concerns about prescribing opioids for chronic pain were prescription drug abuse and addiction. Other concerns included: adverse effects, tolerance, interaction with other medications, not knowing enough about which narcotic to prescribe, not knowing enough about dosage requirements, and having partners who prefer not to use opioids for treating chronic pain. The majority of the physicians were comfortable in prescribing narcotics to someone with terminal cancer, but were less confident in prescribing for patients with back pain. They were even less comfortable with prescribing narcotics to patients with a past history of drug or alcohol abuse.
The survey also noted that only a small percentage of physicians are conducting urine toxicology screens on their patients either before or during opioid therapy, and that this was dependent on whether or not they had a system to track patients on opioids.
- WHAT IT MEANS: Although opioids are effective in treating chronic pain, many physicians have concerns about prescribing them. There is a need for management guidelines that are straightforward and effective in addressing the issues faced by primary care physicians. Research is needed to assess the use of clinical guidelines and other clinic-based approaches to address physician concerns about abuse of opioids.
The study, led by Dr. Bhushan Bhamb, was published in the September 2006 issue of Current Medical Opinion and Research.
Researchers Assess Adolescents’ Motivations To Abuse Prescription Medications
The nonmedical use of prescription drugs is a serious health problem among U.S. youth. University of Michigan scientists surveyed almost 1,100 middle and high school students in one southeastern Michigan school district to determine why students engage in the nonmedical use of four classes of prescription medications (sleep aids, sedatives/anxiolytics, stimulants, and opioid analgesics) and to examine if such motivations were associated with a higher risk of substance abuse problems.
The researchers found that 12 percent of the respondents had engaged in the nonmedical use of opioid pain medications during the previous 12 months. In addition, three percent had nonmedically used sleeping medications, two percent had nonmedically used sedatives/tranquilizers, and two percent had nonmedically used stimulants.
Motivations varied by drug classification. Although 69 percent of respondents who used pain medications used them solely for pain control and 79 percent endorsed pain relief as at least one motivation for their use, 11 percent said they used the drugs to get high. For the nonmedical use of stimulant medications, 29 percent gave only one motive to use stimulants (i.e., to help with concentration or alertness) and 21 percent endorsed several motivations, the most frequently mentioned of which were to "get high," "help with concentration," or "increase my alertness." The most frequently cited reasons for the use of sedatives and tranquilizers were to help with sleep, to decrease anxiety, and to get high.
The researchers also found evidence that the nonmedical use of prescription medications is associated with an increase in general substance abuse problems, particularly with opioid analgesics. When the students noted multiple motivations for the nonmedical use of prescription opioid medications, the scientists observed that each additional motivation carried a greater likelihood of scoring higher on the Drug Abuse Screening Test (DAST-10). However, the authors suggest that there may be two distinct groups of non-medical users of prescription drugs?those who self-medicate and those who use for other reasons, including to experiment and get high. The latter seem to be at greater risk for other forms of substance abuse.
- WHAT IT MEANS: This study further emphasizes the problem of prescription drug abuse among the Nation’s youth, highlighting the motivations for abuse of these medications and their link to future substance abuse problems. These findings suggest that future research is necessary to better understand the reasons for the nonmedical use of prescription medications and to evaluate which nonmedical prescription drug abusers are at greatest risk for developing further substance abuse problems.
Dr. Carol Boyd and her colleagues published their findings in the December 2006 issue of Pediatrics.
Study Reveals a New Cellular Adaptation that Contributes to Opiate Tolerance
Opiate drugs, such as morphine, are considered the gold standard for treating severe pain. They bind to specific receptors in the brain and spinal cord to inhibit the transmission of pain signals. However, prolonged or repeated use of these drugs can produce a tolerance to their effects, requiring more of the drug to achieve the desired effect. Now, NIDAsupported research reveals a new mechanism that may account for important features of opiate tolerance in rats.
Dr. Gregory Terman, of the University of Washington School of Medicine, and his colleagues induced opiate tolerance by injecting increasing amounts of morphine into two-week old rat pups, for six days. They then investigated the electrophysiological properties of neurons in their spinal cords and compared them to those in the spinal cords of control pups that had not been exposed to the drug. They found that spinal cord cells from the tolerant pups were much more excitable than cells from control pups.
Further examination showed that these over-excitable cells were surrounded by more fibers containing larger than normal numbers of NMDA receptors, a subtype of glutamate receptor. The authors suggest that these enhanced levels of NMDA receptors are involved in the transmission of pain signals, and that this adaptive change makes those neurons much more likely to convey pain signals.
Importantly, these new NMDA receptors in the spinal cord of opiate tolerant animals were located upstream of the cells being recorded (i.e., on the cell before the synapse—the junction between nerve cells). The distinct properties of these receptors make them potentially interesting targets for the development of medications to reverse opiate tolerance. Indeed, a preliminary experiment showed that blocking NMDA receptors with a specific NMDA antagonist inhibited the expression of morphine analgesic tolerance without disrupting pain responses.
- WHAT IT MEANS: Previous studies have shown that NMDA receptors play a role in the development of tolerance to opiate pain relievers. This new research suggests that an increase in anatomically and functionally distinct NMDA receptors, produced by repeated exposure to opiate drugs, can enhance excitatory signaling in the spinal cord. These new receptors represent novel potential targets for agents capable of reversing opiate tolerance. Studies seeking to more fully define the biochemical and physiological characteristics of these NMDA receptors in the spinal cord are ongoing.
The scientists published their findings in the November 15, 2006 issue of the Journal of Neuroscience.
URB597 Relieves Pain in Rats Without Cannabinoid-Associated Side Effects
Findings in rats suggest that a compound called URB597, a fatty acid amide hydrolase (FAAH) inhibitor, relieves pain by blocking the breakdown of endocannabinoids, naturally occurring molecules that act on cannabinoid receptors. Cannabinoid receptors are a class of receptors in the brain that recognize THC, the active ingredient in marijuana.
Dr. Christopher Vaughan and his colleagues at the University of Sydney and the University of California at Irvine compared the effects of URB597 and HU210, which directly activates cannabinoid receptors in the brain.
The scientists found that in rats, both compounds reduced inflammatory pain. However, HU210 also reduced motor performance, measured by the time the animals were able to stay on a rotating bar after being given the drug. In contrast, HU210, but not URB597, was effective in reducing neuropathic pain. The scientists say the findings suggest that URB597 produces cannabinoid receptor-mediated pain relief, specifically with respect to inflammatory pain, without causing the undesirable motor effects associated with cannabinoid receptor activation.
- WHAT IT MEANS: This rat study shows that the FAAH inhibitor URB597, like the cannabinoid-receptor activator HU210, was able to provide analgesia in a model of inflammatory pain. Unlike HU210, though, URB597 did not produce side effects generally associated with cannabinoid drugs. The findings suggest that FAAH inhibitors may be a promising class of compounds for pain relief, with fewer side effects than those produced by globally acting cannabinoid agonists.
The study was published in the February 2006 issue of the British Journal of Pharmacology.
Managing the Impact of Pain: Antidepressants May Be Useful Part of Pain Therapy
Scientists from the University of Kansas Medical Center have found that nonsteroidal anti-inflammatory drugs (NSAIDs) and certain types of antidepressants both affect gene expression within the spinal cord, and that antidepressants also affect brain regions involved in the emotional and cognitive aspects of pain.
Dr. Vanja Duric and Dr. Kenneth McCarson pretreated rats with the NSAID indomethacin or the tricyclic antidepressant imipramine. They then injected a substance into the animals to cause inflammatory pain or immobilized them to cause stress. When the researchers examined cells from the rats’ spinal cords and brains they observed that NSAID treatment reduced spinal cord pain transmission, as well as reversing pain-evoked upregulation (switching on of a particular gene leading to increased production of a certain protein) of NK-1 receptors and BDNF gene expression in the spinal cord to levels similar to those seen in control animals. However, indomethacin was unable to prevent the impact of pain on the hippocampus (a part of the brain involved in learning, emotion, and the formation of memories). Conversely, imipramine did not provide significant pain relief whereas it significantly blocked both pain- and stress-evoked alterations in hippocampal and spinal NK-1 and BDNF gene expression.
- WHAT IT MEANS: These results show that neither the NSAID nor the antidepressant alone fully protect against pain processing in the brain and spinal cord. Whereas indomethacin may reduce the sensory experience of pain at the level of the spinal cord, it may have little effect on the negative emotional and cognitive impact of pain. In contrast, imipramine appears to block the expression of long-term changes in both the spinal cord and certain brain regions. The findings suggest that early antidepressant drug administration as part of therapy for persistent pain may prevent predisposition toward development of pain-related depression.
The study was published in the December 2006 issue of the Journal of Pharmacology and Experimental Therapeutics.