Abstract
In the past, management of pain was more empirical but with the understanding of mechanisms, biochemistry and molecular basis of pain, future drug development will be more rational. This article provides a brief overview of the pathomechanism of pain, the clinical situation, current treatments and methods of evaluation of pain therapies such as measurement of pain in clinical trials. A wide spectrum of agents are available, including non-steroid anti-inflammatory drugs (NSAIDs), opioids and adjuvant analgesics, such as antidepressants and certain anticonvulsants that are useful in neuropathic pain. Current management of pain is inadequate due to lack of understanding of pain mechanisms by healthcare providers and the lack of availability of adequate analgesic medications. Acute pain, if treated inadequately, changes into chronic pain with changes in the nervous system. Chronic pain, particularly neuropathic pain, is a neurological disorder, which is more difficult to treat. The total value of the pain management market, including drugs and devices, is estimated to be $5 billion in the year 2000, and will increase to $9 billion in the year 2005. A large number of drugs in development for pain include opioid receptor agonists and antagonists of glutamate receptors, adenosine triphosphate (ATP), serotonin (5-HT) and vanilloid receptors (VR1). Analgesics acting on ion channels and NSAIDs, which inhibit the cyclooxygenase (COX) pathways, are still in development. The ideal analgesic is defined and methods of pain drug delivery are also reviewed. A novel compound with an effective method of delivery has a better chance in the competitive marketplace of analgesic drug development.