Pain is the most common reason people visit a doctor. When treating pain, physicians have long wrestled with a dilemma: How can a doctor relieve a patient's suffering while avoiding the potential for that patient to become addicted to a powerful, opiate pain medication?
Today, the medical profession has concluded that many doctors underprescribe powerful painkillers because they overestimate the potential for patients to become addicted to these painkillers, which include opiates (from opium) such as morphine and codeine, and substances that are structurally related to morphine. The term "opioids" is used to describe the entire class (both synthetic and natural) of chemicals structurally similar to morphine. Although these drugs carry an extreme risk of addiction for many people, many physicians are not aware that these drugs are rarely abused when used for medicinal purposes.
When doctors limit pain medication, thousands of patients suffer needlessly, according to a number of studies. This quandary over the prescription of powerful pain relievers continues while investigators search for new ways to control pain. NIDA-funded researchers are spearheading the exploration for new painkillers that are effective but nonaddicting.
Opium, the bitter dried juice of the opium poppy, has been used for centuries to relieve pain. Opium's analgesic properties come from morphine, opium's major active component.
In the 1970s and 1980s, researchers discovered morphine-like substances that occur naturally in the body, the endogenous opioid peptides.
However, the debilitating side effects that opiate medications can produce, such as nausea, sedation, confusion, and constipation, limit their effectiveness and contribute to the need for alternative analgesics.
NIDA-supported researchers are addressing this need through a number of experimental approaches. These include:
- Developing opioid compounds, syn thetic derivatives of opiates, that promote pain relief without producing the euphoria, or "high," that can lead to addiction
- Developing "promoter compounds" that enhance the pain-relieving effects of opioids so that smaller doses can be used
- Developing nonopioid analgesics that function through different pain-relief processes and presumably will not produce the negative side effects of opioids
Years of research have uncovered three categories of opioids: agonists, such as Demerol and methadone, that mimic the effects of endogenous opioids; antagonists, such as naloxone, that block certain effects of opioids; and mixed agonist-antagonist opioid agents, such as buprenorphine and nalbuphine, that both activate and block specific opioid effects. These partial agonists-buprenorphine and nalbuphine- minimize the agonists' negative side effects, including sedation, respiratory problems, and abuse potential, while relieving pain.
Opiates, including morphine and codeine, and synthetic opioids, such as Demerol and fentanyl, work by mimicking the endogenous opioid peptides, pain-relieving chemicals produced in the body. These peptides bind chemically to opiate receptors, activating pain-relieving systems in the brain and spinal cord. But opioids can cause undesirable side effects such as nausea, sedation, confusion, and constipation. With prolonged use of opiates and opioids, individuals become tolerant to the drugs, require larger doses, and can become physically dependent on the drugs.
In recent years, research has shown that doctors' fears that patients will become addicted to pain medication, known as "opiophobia," are largely unfounded. Studies indicate that most patients who receive opioids for pain, even those undergoing long-term therapy, do not become addicted to these drugs. The very few patients who develop rapid and marked tolerance and addiction to opioids are usually those who have a history of psychological problems or prior substance abuse.
One study found that only four out of more than 12,000 patients who were given opioids for acute pain actually became addicted to the drugs. Even long-term therapy has limited potential for addiction. In a study of 38 chronic pain patients, most of whom received opioids for 4 to 7 years, only 2 patients actually became addicted, and both had a history of drug abuse.
The problem of underprescription of opiates and opioids and the accompanying
needless suffering for millions of patients has prompted official reaction.
In 1992 the Federal Agency for Health Care Policy and Research issued guidelines
for the treatment of pain. The recommendations encourage health professionals
to ignore myths about addiction to pain medications and to cease groundless
restrictions on the dispensing of opioid pain relievers. The guidelines
also recommend greater use of intravenous drug "pumps," which
allow nurses or patients themselves to control the timing and dosage of
the drug being taken. Following the guidelines, the agency said, would
not only relieve unnecessary suffering, but would speed patients' recovery
and reduce hospital stays and costs.
National Institute on Drug Abuse