An analgesic drug, also called simply an analgesic, antalgic, pain reliever, or painkiller, is any member of the group of drugs used for pain management. Analgesics are conceptually distinct from anesthetics, which temporarily reduce, and in some instances eliminate, sensation, although analgesia and anesthesia are neurophysiologically overlapping and thus various drugs have both analgesic and anesthetic effects.
Tricyclic antidepressants (TCAs) are a class of medications that are used primarily as antidepressants. TCAs were discovered in the early 1950s and were marketed later in the decade. They are named after their chemical structure, which contains three rings of atoms. Tetracyclic antidepressants (TeCAs), which contain four rings of atoms, are a closely related group of antidepressant compounds.
Postherpetic neuralgia (PHN) is neuropathic pain that occurs due to damage to a peripheral nerve caused by the reactivation of the varicella zoster virus. PHN is defined as pain in a dermatomal distribution that lasts for at least 90 days after an outbreak of herpes zoster. Several types of pain may occur with PHN including continuous burning pain, episodes of severe shooting or electric-like pain, and a heightened sensitivity to gentle touch which would not otherwise cause pain or to painful stimuli. Abnormal sensations and itching may also occur.
Neuropathic pain is pain caused by a lesion or disease of the somatosensory nervous system. Neuropathic pain may be associated with abnormal sensations called dysesthesia or pain from normally non-painful stimuli (allodynia). It may have continuous and/or episodic (paroxysmal) components. The latter resemble stabbings or electric shocks. Common qualities include burning or coldness, "pins and needles" sensations, numbness and itching.
Neuropharmacology is the study of how drugs affect function in the nervous system, and the neural mechanisms through which they influence behavior. There are two main branches of neuropharmacology: behavioral and molecular. Behavioral neuropharmacology focuses on the study of how drugs affect human behavior (neuropsychopharmacology), including the study of how drug dependence and addiction affect the human brain. Molecular neuropharmacology involves the study of neurons and their neurochemical interactions, with the overall goal of developing drugs that have beneficial effects on neurological function. Both of these fields are closely connected, since both are concerned with the interactions of neurotransmitters, neuropeptides, neurohormones, neuromodulators, enzymes, second messengers, co-transporters, ion channels, and receptor proteins in the central and peripheral nervous systems. Studying these interactions, researchers are developing drugs to treat many different neurological disorders, including pain, neurodegenerative diseases such as Parkinson's disease and Alzheimer's disease, psychological disorders, addiction, and many others.
Orphenadrine is an anticholinergic drug of the ethanolamine antihistamine class; it is closely related to diphenhydramine. It is a muscle relaxant that is used to treat muscle pain and to help with motor control in Parkinson's disease, but has largely been superseded by newer drugs. It is considered a dirty drug due to its multiple mechanisms of action in different pathways. It was discovered and developed in the 1940s.
Sodium voltage-gated channel alpha subunit 9 is a sodium ion channel that in humans is encoded by the SCN9A gene. It is usually expressed at high levels in two types of neurons: the nociceptive (pain) neurons at the dorsal root ganglion (DRG) and trigeminal ganglion; and sympathetic ganglion neurons, which are part of the autonomic (involuntary) nervous system.
Group C nerve fibers are one of three classes of nerve fiber in the central nervous system (CNS) and peripheral nervous system (PNS). The C group fibers are unmyelinated and have a small diameter and low conduction velocity, whereas Groups A and B are myelinated. Group C fibers include postganglionic fibers in the autonomic nervous system (ANS), and nerve fibers at the dorsal roots. These fibers carry sensory information.
Nefopam, sold under the brand name Acupan among others, is a centrally acting, non-opioid painkilling medication, with central stimulant and sympathomimetic properties that is primarily used to treat moderate to severe pain.
Sodium channel blockers are drugs which impair the conduction of sodium ions (Na+) through sodium channels.
Safinamide, sold under the brand name Xadago, is a medication used as treatment for Parkinson's disease with "off" episodes; it has multiple modes of action, including the inhibition of monoamine oxidase B.
Indantadol is a drug which was formerly being investigated as an anticonvulsant and neuroprotective and is now under development for the treatment of neuropathic pain and chronic cough in Europe by Vernalis and Chiesi. It acts as a competitive, reversible, and non-selective monoamine oxidase inhibitor, and as a low affinity, non-competitive NMDA receptor antagonist. A pilot study of indantadol for chronic cough was initiated in October 2009 and in April 2010 it failed to achieve significant efficacy in neuropathic pain in phase IIb clinical trials.
Min Zhuo is a pain neuroscientist at the University of Toronto in Canada. He is the Michael Smith Chair in Neuroscience and Mental Health as well as the Canada Research Chair in Pain and Cognition and a Fellow of the Royal Society of Canada. Zhou was hosted in 2017-2018 as a guest professor at the pharmacology institute at Heidelberg University, Heidelberg.
Funapide (INN) is a novel analgesic under development by Xenon Pharmaceuticals for the treatment of a variety of chronic pain conditions, including osteoarthritis, neuropathic pain, postherpetic neuralgia, and erythromelalgia, as well as dental pain. It acts as a small-molecule Nav1.7 and Nav1.8 voltage-gated sodium channel blocker. Funapide is being evaluated in humans in both oral and topical formulations, and as of July 2014, has reached phase IIb clinical trials.
Vixotrigine, formerly known as raxatrigine, is an analgesic which is under development by Convergence Pharmaceuticals for the treatment of lumbosacral radiculopathy (sciatica) and trigeminal neuralgia (TGN). Vixotrigine was originally claimed to be a selective central Nav1.3 blocker, but was subsequently redefined as a selective peripheral Nav1.7 blocker. Following this, vixotrigine was redefined once again, as a non-selective voltage-gated sodium channel blocker. As of January 2018, it is in phase III clinical trials for trigeminal neuralgia and is in phase II clinical studies for erythromelalgia and neuropathic pain. It was previously under investigation for the treatment of bipolar disorder, but development for this indication was discontinued.
DSP-2230 is a selective small-molecule Nav1.7 and Nav1.8 voltage-gated sodium channel blocker which is under development by Dainippon Sumitomo Pharma for the treatment of neuropathic pain. As of June 2014, it is in phase I/phase II clinical trials.
Leconotide is an ω-conotoxin peptide isolated from the venom of Conus catus which is under investigation as an analgesic drug for the treatment of pain conditions.
Evenamide is a selective voltage-gated sodium channel blocker, including subtypes Nav1.3, Nav1.7, and Nav1.8, which is described as an antipsychotic and is under development by Newron Pharmaceuticals as an add-on therapy for the treatment of schizophrenia. The drug has shown efficacy in animal models of psychosis, mania, depression, and aggression. It has completed phase I clinical trials, and phase II clinical trials will be commenced in the third quarter of 2015.
An analgesic adjuvant is a medication that is typically used for indications other than pain control but provides control of pain (analgesia) in some painful diseases. This is often part of multimodal analgesia, where one of the intentions is to minimize the need for opioids.
