Drug – bio-affecting and body treating compositions – Antigen – epitope – or other immunospecific immunoeffector – Bacterium or component thereof or substance produced by said...
Reexamination Certificate
2000-04-14
2002-10-15
Carlson, Karen Cochrane (Department: 1653)
Drug, bio-affecting and body treating compositions
Antigen, epitope, or other immunospecific immunoeffector
Bacterium or component thereof or substance produced by said...
C424S239100, C424S236100, C435S252700, C514S002600, C514S012200, C530S350000
Reexamination Certificate
active
06464986
ABSTRACT:
BACKGROUND
The present invention relates to methods for treating pain. In particular, the present invention relates to methods for treating pain by peripheral administration of a neurotoxin.
Many, if not most ailments of the body cause pain. Generally pain is experienced when the free nerve endings which constitute the pain receptors in the skin as well as in certain internal tissues are subjected to mechanical, thermal, chemical or other noxious stimuli. The pain receptors can transmit signals along afferent neurons into the central nervous system and thence to the brain.
The causes of pain can include inflammation, injury, disease, muscle spasm and the onset of a neuropathic event or syndrome. Ineffectively treated pain can be devastating to the person experiencing it by limiting function, reducing mobility, complicating sleep, and dramatically interfering with the quality of life.
A muscle spasm can led to stimulation of mechanosensitive pain receptors thereby causing a sensation of pain. Thus, pain can arise from or be due to a muscle spasm. Additionally, the spasm can indirectly stimulate the pain receptors by compressing onto blood vessels, causing ischemia in the tissue, which in turn releases pain inducing substances that stimulate pain receptors to cause pain sensations. Furthermore, a muscle spasm can cause a localized pH reduction which can be perceived as or which can engender pain signals. Hence, pain can be a secondary effect of a muscle spasm or muscle hypertonicity.
Inflammatory pain can occur when tissue is damaged, as can result from surgery or due to an adverse physical, chemical or thermal event or to infection by a biologic agent. When a tissue is damaged, a host of endogenous pain inducing substances, for example bradykinin and histamine can be released from the injured tissue. The pain inducing substances can bind to receptors on the sensory nerve terminals and thereby initiate afferent pain signals.
Additionally, pain inducing substances can be released from nociceptive afferent terminals, and neuropeptides released from sensory terminals can accentuate an inflammatory response. Thus, during inflammation there can be a sprouting of peptidergic peripheral fibers and an increased content of peptide, with many fibers showing a coexistence of substance P (SP) and calcitonin gene related peptide (CGRP). Substance P can induce contraction of endothelia cells, which in turn causes plasma extravasation to allow other substances (bradykinin, ATP, histamine) to gain access to the cite of injury and the afferent nerve terminals. Substance P release by the sensory nerve terminal can also degranulate mast cell. This process has been considered to be an important factor in neurogenic inflammation due to the release of inflammatory mediators such as histamine and serotonin and the release of proteolytic enzymes which catalyze the production of bradykinin. CGRP apparently does not produce plasma extravasation but is a powerful vasodilator and also act synergistically with SP and other inflammatory mediators to enhance plasma extravasation. All the above listed inflammatory mediators can either sensitize nociceptors or produce pain.
After activation of the primary sensory afferent neurons the next step in the transduction of sensory signals can be activation of projection neurons, which carry the signal, via the spinothalamic tract, to higher parts of the central nervous system such as the thalamic nuclei. The cell bodies of these neurons (other than those related to the cranial nerves) are located in the dorsal horn of the spinal cord. Here also one can find the synapses between the primary afferents and the projection neurons. The dorsal horn is organized into a series of laminae that are stacked, with lamina I being most dorsal followed by lamina II, etc. The different classes of primary afferents make synapses in different laminae. For cutaneous primary afferents, C-fibers make synapses in laminae I and II, A delta-fibers in laminae I, II, and V, and A beta-fibers in laminae III, IV, and V. Deeper laminae (V-VII, X) are thought to be involved in the sensory pathways arriving from deeper tissues such as muscles and the viscera.
The predominant neurotransmitters at the synapses between primary afferent neurons and projection neurons are substance P, glutamate, CGRP and neuropeptide Y. The efficiency of transmission of these synapses can be altered via descending pathways and by local interneurons in the spinal cord. These modulatory neurons can release a number of mediators that are either inhibitory (e.g. opioid peptides, glycine) or excitatory (e.g. nitric oxide, cholecystokinin), to provide a mechanism for enhancing or reducing awareness of sensations.
Although inflammatory pain is generally reversible and subsides when the injured tissue has been repaired or the pain inducing stimulus removed, present methods for treating inflammatory pain have many drawbacks and deficiencies. Thus, the typical oral, parenteral or topical administration of an analgesic drug to treat the symptoms of pain or of, for example, an antibiotic to treat inflammatory pain causation factors can result in widespread systemic distribution of the drug and undesirable side effects. Additionally, current therapy for inflammatory pain suffers from short drug efficacy durations which necessitate frequent drug re-administration with possible resulting drug resistance, antibody development and/or drug dependence and addiction, all of which are unsatisfactory. Furthermore, frequent drug administration increases the expense of the regimen to the patient and can require the patient to remember to adhere to a dosing schedule.
Examples of treatments for inflammation and muscle pain include non-steroidal anti-inflammatory drugs (NSAIDS), including aspirin and ibuprofen; and opioids, such as morphine.
NSAIDs alleviate pain by inhibiting the production of prostaglandins released by damaged tissues. Prostaglandins have been shown to be peripheral mediators of pain and inflammation, as in arthritic diseases, and a reduction in their concentration provides relief to patients. It has been suggested that prostaglandins are involved in the mediation of pain in the spinal cord and the brain, which may explain the analgesic effects of NSAIDS in some pain states that do not involve inflammation or peripheral tissue damage. However, prostaglandins are only one of several mediators of pain. As such, NSAIDs have a ceiling of activity above which increasing doses do not give more pain relief. Furthermore, they have side effects that limit their usefulness. For example, NSAIDs can cause irritation of the gastrointestinal tract and prolonged use may lead to the development of extensive ulceration of the gut. This is particularly true in elderly patients who frequently use NSAIDs for their arthritis conditions.
The therapeutic actions of opioids are in the spinal cord. Opioids inhibit the efficiency of neurotransmission between the primary sensory afferents (principally C-fibers) and the projection neurons. They achieve this by causing a prolonged hyperpolarization of both elements of these synapses. The use of opioids is effective in alleviating most types of acute pain and chronic malignant pain. There are, however, a number of chronic malignant pain conditions which are partly or completely refractory to opioid analgesia, particularly those which involve nerve compression, e.g. by tumor formation. Unfortunately opioids also have unwanted side-effects including: (1) depression of the respiratory system, (2) constipation, and (3) psychoactive effects including sedation and euphoria. These side effects occur at doses similar to those that produce analgesia and therefore limit the doses that can be given to patients. Additionally, opioids such as morphine and heroin are well-known drugs of abuse that lead to physical dependence, which also involves the development of tolerance. With the development of tolerance, the dose of a drug required to produce the same analgesic effect increases with time. This may lead to a conditi
Aoki Kei Roger
Cui Minglei
Jenkins Stephen W.
Allegan Sales, Inc.
Carlson Karen Cochrane
Donovan Stephen
Kam Chih-Min
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