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Trade names | Neurontin, others [1] |
Other names | CI-945; GOE-3450; DM-1796 (Gralise) |
AHFS/Drugs.com | Monograph |
MedlinePlus | a694007 |
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Dependence liability | Physical: High [3] Psychological: Moderate |
Addiction liability | Low [4] |
Routes of administration | By mouth |
Drug class | Gabapentinoid |
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Pharmacokinetic data | |
Bioavailability | 27–60% (inversely proportional to dose; a high fat meal also increases bioavailability) [8] [9] |
Protein binding | Less than 3% [8] [9] |
Metabolism | Not significantly metabolized [8] [9] |
Elimination half-life | 5 to 7 hours [8] [9] |
Excretion | Kidney [8] [9] |
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KEGG | |
ChEBI | |
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CompTox Dashboard (EPA) | |
ECHA InfoCard | 100.056.415 |
Chemical and physical data | |
Formula | C9H17NO2 |
Molar mass | 171.240 g·mol−1 |
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Gabapentin, sold under the brand name Neurontin among others, is an anticonvulsant medication primarily used to treat partial seizures and neuropathic pain. [7] [10] It is a commonly used medication for the treatment of neuropathic pain caused by diabetic neuropathy, postherpetic neuralgia, and central pain. [11] It is moderately effective: about 30–40% of those given gabapentin for diabetic neuropathy or postherpetic neuralgia have a meaningful benefit. [12]
Sleepiness and dizziness are the most common side effects. Serious side effects include an increased risk of suicide, respiratory depression, and allergic reactions. [7] Lower doses are recommended in those with kidney disease. [7] Gabapentin acts by decreasing activity of a subset of calcium channels. [13] [14] [15]
Gabapentin was first approved for use in 1993. [16] It has been available as a generic medication in the United States since 2004. [17] In 2021, it was the tenth most commonly prescribed medication in the United States, with more than 47 million prescriptions. [18] [19] During the 1990s, Parke-Davis, a subsidiary of Pfizer, used a number of illegal techniques to encourage physicians in the United States to prescribe gabapentin for unapproved uses. [20] They have paid out millions of dollars to settle lawsuits regarding these activities. [21]
Gabapentin is recommended for use in focal seizures and neuropathic pain. [7] [10] Gabapentin is prescribed off-label in the US and the UK, [22] [23] for example, for the treatment of non-neuropathic pain, [22] anxiety disorders and bipolar disorder. [24] There is concern regarding gabapentin's off-label use due to the lack of strong scientific evidence for its efficacy in multiple conditions, its proven side effects and is potential for misuse and physical/psychological dependency. [25] [26] [27]
Gabapentin is approved for the treatment of focal seizures; [28] however, it is not effective for generalized epilepsy. [29]
Gabapentin is recommended as a first-line treatment for chronic neuropathic pain by various medical authorities. [10] [11] [30] [31] This is a general recommendation applicable to all neuropathic pain syndromes except for trigeminal neuralgia, where it may be used as a second- or third-line agent. [11] [31]
In regard to the specific diagnoses, a systematic review has found evidence for gabapentin to provide pain relief for some people with postherpetic neuralgia and diabetic neuropathy. [12] Gabapentin is approved for the former indication in the US. [7] In addition to these two neuropathies, European Federation of Neurological Societies guideline notes gabapentin effectiveness for central pain. [11] A combination of gabapentin with an opioid or nortriptyline may work better than either drug alone. [11] [31]
Gabapentin shows substantial benefit (at least 50% pain relief or a patient global impression of change (PGIC) "very much improved") for neuropathic pain (postherpetic neuralgia or peripheral diabetic neuropathy) in 30–40% of subjects treated as compared to those treated with placebo. [12]
Evidence finds little or no benefit and significant risk in those with chronic low back pain or sciatica. [32] [33] Gabapentin is not effective in HIV-associated sensory neuropathy [34] and neuropathic pain due to cancer. [35]
There is a small amount of research on the use of gabapentin for the treatment of anxiety disorders. [36] [37]
Gabapentin is effective for the long-term treatment of social anxiety disorder and in reducing preoperative anxiety. [25] [26]
In a controlled trial of breast cancer survivors with anxiety, [37] and in a trial for social phobia, [36] gabapentin significantly reduced anxiety levels.
For panic disorder, gabapentin has produced mixed results. [37] [36] [26]
Gabapentin is effective in treating sleep disorders such as insomnia and restless legs syndrome that are the result of an underlying illness, but comes with some risk of discontinuation and withdrawal symptoms after prolonged use at higher doses. [38]
Gabapentin enhances slow-wave sleep in people with primary insomnia. It also improves sleep quality by elevating sleep efficiency and decreasing spontaneous arousal. [39]
Gabapentin is moderately effective in reducing the symptoms of alcohol withdrawal and associated craving. [40] [41] [42] The evidence in favor of gabapentin is weak in the treatment of alcoholism: it does not contribute to the achievement of abstinence, and the data on the relapse of heavy drinking and percent of days abstinent do not robustly favor gabapentin; it only decreases the percent days of heavy drinking. [43]
Gabapentin is ineffective in cocaine dependence and methamphetamine use, [44] and it does not increase the rate of smoking cessation. [45] While some studies indicate that gabapentin does not significantly reduce the symptoms of opiate withdrawal, there is increasing evidence that gabapentinoids are effective in controlling some of the symptoms during opiate detoxification. A clinical study in Iran, where heroin dependence is a significant social and public health problem, showed gabapentin produced positive results during an inpatient therapy program, particularly by reducing opioid-induced hyperalgesia and drug craving. [46] [44] There is insufficient evidence for its use in cannabis dependence. [47]
Gabapentin is recommended as a first-line treatment of the acquired pendular nystagmus, torsional nystagmus, and infantile nystagmus; however, it does not work in periodic alternating nystagmus. [48] [49] [50]
Gabapentin decreases the frequency of hot flashes in both menopausal women and people with breast cancer. However, antidepressants have similar efficacy, and treatment with estrogen more effectively prevents hot flashes. [51]
Gabapentin reduces spasticity in multiple sclerosis and is prescribed as one of the first-line options. [52] It is an established treatment of restless legs syndrome. [53] Gabapentin alleviates itching in kidney failure (uremic pruritus) [54] [55] and itching of other causes. [56] It may be an option in essential or orthostatic tremor. [57] [58] [59] Although the efficacy of gabapentin for insomnia has not been established, it does alleviate sleep disorder in people with medical illness. [38]
Gabapentin does not appear to provide benefit for bipolar disorder, [26] [41] [60] complex regional pain syndrome, [61] post-surgical pain, [62] or tinnitus, [63] or prevent episodic migraine in adults. [64]
Gabapentin should be used carefully and at lower doses in people with kidney problems due to possible accumulation and toxicity. It is unclear if it is safe during pregnancy or breastfeeding. [7]
Dizziness and somnolence are the most frequent side effects. [7] Fatigue, ataxia, peripheral edema (swelling of extremities), and nystagmus are also common. [7] A 2017 meta-analysis found that gabapentin also increased the risk of difficulties in mentation and visual disturbances as compared against a placebo. [65] Gabapentin is associated with a weight gain of 2.2 kg (4.9 lb) after 1.5 months of use. [66] Case studies indicate that it may cause anorgasmia and erectile dysfunction, [67] as well as myoclonus [68] [69] that disappear after discontinuing gabapentin or replacing it with other medication. DRESS [ citation needed ], fever, swollen glands that do not go away, eyes or skin turning yellow, unusual bruises or bleeding, unexpected muscle pain or weakness, rash, long-lasting stomach pain which may indicate an inflamed pancreas, hallucinations, anaphylaxis, respiratory depression, and increased suicidal ideation are rare but serious side effects. [70]
The gabapentin label contains a warning of an increased risk of suicidal thoughts and behaviors. [7] According to an insurance claims database study, gabapentin use is associated with about 40% increased risk of suicide, suicide attempt and violent death as compared with a reference anticonvulsant drug topiramate. The risk is increased for people with bipolar disorder or epilepsy. [71] Another study has shown an approximately doubled rate of suicide attempts and self-harm in people with bipolar disorder who are taking gabapentin versus those taking lithium. [72] A large Swedish study suggests that gabapentinoids are associated with an increased risk of suicidal behaviour, unintentional overdoses, head/body injuries, and road traffic incidents and offences. [73] On the other hand, a study published by the Harvard Data Science Review found that gabapentin was associated with a significantly reduced rate of suicide. [74]
Serious breathing suppression, potentially fatal, may occur when gabapentin is taken together with opioids, benzodiazepines, or other depressants, or by people with underlying lung problems such as COPD. [75] [76] Gabapentin and opioids are commonly prescribed or abused together, and research indicates that the breathing suppression they cause is additive. For example, gabapentin use before joint replacement or laparoscopic surgery increased the risk of respiratory depression by 30–60%. [75] A Canadian study showed that use of gabapentin and other gabapentinoids, whether for epilepsy, neuropathic pain or other chronic pain was associated with a 35–58% increased risk for severe exacerbation of pre-existing chronic obstructive pulmonary disease. [77]
Withdrawal symptoms typically occur 1–2 days after abruptly stopping gabapentin (almost unambiguously due to extended use and during a very short-term rebound phenomenon) — similar to, albeit less intense than most benzodiazepines. [78] Agitation, confusion and disorientation are the most frequently reported, followed by gastrointestinal complaints and sweating, and more rare tremor, tachycardia, hypertension and insomnia. [78] In some cases, users experience withdrawal seizures after chronic or semi-chronic use in the absence of periodic cycles or breaks during repeating and consecutive use. [79] All these symptoms subside when gabapentin is re-instated [78] or tapered off gradually at an appropriate rate.[ citation needed ]
On its own, gabapentin appears to not have a substantial addictive power. In human and animal experiments, it shows limited to no rewarding effects. The vast majority of people abusing gabapentin are current or former abusers of opioids or sedatives. [79] In these persons, gabapentin can boost the opioid "high" as well as decrease commonly experienced opioid-withdrawal symptoms such as anxiety. [80]
Through excessive ingestion, accidental or otherwise, persons may experience overdose symptoms including drowsiness, sedation, blurred vision, slurred speech, somnolence, uncontrollable jerking motions, and anxiety. A very high amount taken is associated with breathing suppression, coma, and possibly death, particularly if combined with alcohol or opioids. [79] [81]
Gabapentin is a ligand of the α2δ calcium channel subunit. [82] [83] α2δ is an auxiliary protein connected to the main α1 subunit (the channel-forming protein) of high voltage activated voltage-dependent calcium channels (L-type, N-type, P/Q type, and R-type). [13] Gabapentin is not a direct channel blocker: it exerts its actions by disrupting the regulatory function of α2δ and its interactions with other proteins. Gabapentin prevents delivery of the calcium channels to the cell membrane, reduces the activation of the channels by the α2δ subunit, decreases signaling leading to neurotransmitters release, and disrupts interactions of α2δ with NMDA receptors, neurexins, and thrombospondins. [13] [14] [15] Out of the four known isoforms of α2δ protein, gabapentin binds with similar high affinity to two: α2δ-1 and α2δ-2. [83] Most of the pharmacological properties of gabapentin are explained by its binding to just one isoform – α2δ-1. [83] [14]
The endogenous α-amino acids L-leucine and L-isoleucine, which resemble gabapentin in chemical structure, bind α2δ with similar affinity to gabapentin and are present in human cerebrospinal fluid at micromolar concentrations. [84] They may be the endogenous ligands of the α2δ subunit, and they competitively antagonize the effects of gabapentin. [84] [85] Accordingly, while gabapentin has nanomolar affinity for the α2δ subunit, its potency in vivo is in the low micromolar range, and competition for binding by endogenous L-amino acids is likely to be responsible for this discrepancy. [14]
Gabapentin is a potent activator of voltage-gated potassium channels KCNQ3 and KCNQ5, even at low nanomolar concentrations. However, this activation is unlikely to be the dominant mechanism of gabapentin's therapeutic effects. [86]
Gabapentin is structurally similar to the neurotransmitter glutamate and competitively inhibits branched-chain amino acid aminotransferase (BCAT), slowing down the synthesis of glutamate. [87] In particular it inhibits BCAT-1 at high concentrations (Ki = 1 mM), but not BCAT-2. [88] At very high concentrations gabapentin can suppress the growth of cancer cells, presumably by effecting mitochondrial catabolism, however the precise mechanism remains elusive. [88]
Despite the fact that gabapentin is a structural GABA analogue, and in spite of its name, it does not bind to the GABA receptors, does not convert into GABA or another GABA receptor agonist in vivo , and does not modulate GABA transport or metabolism within the range of clinical dosing. [82] In vitro gabapentin has been found to very weakly inhibit the GABA aminotransferase enzymne (Ki = 17–20 mM), however this effect is so weak it is not clinically relevant at prescribed doses. [87]
Gabapentin is absorbed from the intestines by an active transport process mediated via an amino acid transporter, presumably, LAT2. [89] As a result, the pharmacokinetics of gabapentin is dose-dependent, with diminished bioavailability and delayed peak levels at higher doses. [83]
The oral bioavailability of gabapentin is approximately 80% at 100 mg administered three times daily once every 8 hours, but decreases to 60% at 300 mg, 47% at 400 mg, 34% at 800 mg, 33% at 1,200 mg, and 27% at 1,600 mg, all with the same dosing schedule. [7] [90] Drugs that increase the transit time of gabapentin in the small intestine can increase its oral bioavailability; when gabapentin was co-administered with oral morphine, the oral bioavailability of a 600 mg dose of gabapentin increased by 50%. [90]
Gabapentin at a low dose of 100 mg has a Tmax (time to peak levels) of approximately 1.7 hours, while the Tmax increases to 3 to 4 hours at higher doses. [83] Food does not significantly affect the Tmax of gabapentin and increases the Cmax and area-under-curve levels of gabapentin by approximately 10%. [90]
Gabapentin can cross the blood–brain barrier and enter the central nervous system. [82] Gabapentin concentration in cerebrospinal fluid is approximately 9–14% of its blood plasma concentration. [90] Due to its low lipophilicity, [90] gabapentin requires active transport across the blood–brain barrier. [91] [82] [92] [93] The LAT1 is highly expressed at the blood–brain barrier [94] and transports gabapentin across into the brain. [91] [82] [92] [93] As with intestinal absorption mediated by an amino acid transporter, the transport of gabapentin across the blood–brain barrier by LAT1 is saturable. [91] Gabapentin does not bind to other drug transporters such as P-glycoprotein (ABCB1) or OCTN2 (SLC22A5). [91] It is not significantly bound to plasma proteins (<1%). [90]
Gabapentin undergoes little or no metabolism. [83] [90]
Gabapentin is generally safe in people with liver cirrhosis. [95]
Gabapentin is eliminated renally in the urine. [90] It has a relatively short elimination half-life, with the reported average value of 5 to 7 hours. [90] Because of its short elimination half-life, gabapentin must be administered 3 to 4 times per day to maintain therapeutic levels. [96] Gabapentin XR (brand name Gralise) is taken once a day. [97]
Gabapentin is a 3,3-disubstituted derivative of GABA. Therefore, it is a GABA analogue, as well as a γ-amino acid. [98] [99] Specifically, it is a derivative of GABA with a pentyl disubstitution at 3 position, hence, the name - gabapentin, in such a way as to form a six-membered ring. After formation of the ring, the amine and carboxylic groups are not in the same relative positions as they are in the GABA; [100] they are more conformationally constrained. [101]
A process for chemical synthesis and isolation of gabapentin with high yield and purity [102] starts with conversion of 1,1-cyclohexanediacetic anhydride to 1,1-cyclohexanediacetic acid monoamide and is followed by a 'Hofmann' rearrangement in an aqueous solution of sodium hypobromite prepared in situ.
Gabapentin was designed by researchers at Parke-Davis to be an analogue of the neurotransmitter GABA that could more easily cross the blood–brain barrier and was first described in 1975 by Satzinger and Hartenstein. [100] [103] Under the brand name Neurontin, it was first approved in May 1993, for the treatment of epilepsy in the United Kingdom. [104] Approval by the U.S. Food and Drug Administration followed in December 1993, for use as an adjuvant (effective when added to other antiseizure drugs) medication to control partial seizures in adults; that indication was extended to children in 2000. [105] [7] Subsequently, gabapentin was approved in the United States for the treatment of postherpetic neuralgia in 2002. [106] A generic version of gabapentin first became available in the United States in 2004. [17] An extended-release formulation of gabapentin for once-daily administration, under the brand name Gralise, was approved in the United States for the treatment postherpetic neuralgia in January 2011. [107] [108]
Effective April 2019, the United Kingdom reclassified the drug as a class C controlled substance. [109] [110] [111] [112] [113]
Gabapentin is not a controlled substance under the federal Controlled Substances Act. [114] Effective 1 July 2017, Kentucky classified gabapentin as a schedule V controlled substance statewide. [115] Gabapentin is scheduled V drug in other states such as West Virginia, [116] Tennessee, [117] Alabama, [118] Utah, [119] and Virginia. [120]
Although some small, non-controlled studies in the 1990s—mostly sponsored by gabapentin's manufacturer—suggested that treatment for bipolar disorder with gabapentin may be promising, [121] the preponderance of evidence suggests that it is not effective. [122]
Subsequent to the corporate acquisition of the original patent holder, the pharmaceutical company Pfizer admitted that there had been violations of FDA guidelines regarding the promotion of unproven off-label uses for gabapentin in the Franklin v. Parke-Davis case.
While off-label prescriptions are common for a number of drugs, marketing of off-label uses of a drug is not. [20] In 2004, Warner-Lambert (which subsequently was acquired by Pfizer) agreed to plead guilty for activities of its Parke-Davis subsidiary, and to pay $430 million in fines to settle civil and criminal charges regarding the marketing of Neurontin for off-label purposes. The 2004 settlement was one of the largest in U.S. history up to that point, and the first off-label promotion case brought successfully under the False Claims Act. [123]
Kaiser Foundation Hospitals and Kaiser Foundation Health Plan sued Pfizer Inc., alleging that the pharmaceutical company had misled Kaiser by recommending Neurontin as an off-label treatment for certain conditions (including bipolar disorder, migraines, and neuropathic pain). [124] [125] [126] In 2010, a federal jury in Massachusetts ruled in Kaiser's favor, finding that Pfizer violated the federal Racketeer Influenced and Corrupt Organizations (RICO) Act and was liable for US$47.36 million in damages, which was automatically trebled to just under $142.1 million. [125] [124] Aetna, Inc. and a group of employer health plans prevailed in their similar Neurontin-related claims against Pfizer. [127] Pfizer appealed, but the U.S. Court of Appeals for the First Circuit upheld the verdict, [127] and in 2013, the US Supreme Court declined to hear the case. [128] [129]
Gabasync, a treatment consisting of a combination of gabapentin and two other medications (flumazenil and hydroxyzine) as well as therapy, is an ineffective treatment promoted for methamphetamine addiction, though it had also been claimed to be effective for dependence on alcohol or cocaine. [130] It was marketed as PROMETA. While the individual drugs had been approved by the FDA, their off-label use for addiction treatment has not. [131] Gabasync was marketed by Hythiam, Inc. which is owned by Terren Peizer, a former junk bond salesman who has since been indicted for securities fraud relative to another company. [132] [130] Hythiam charges up to $15,000 per patient to license its use (of which half goes to the prescribing physician, and half to Hythiam). [133]
In November 2011, the results of a double-blind, placebo-controlled study (financed by Hythiam and carried out at UCLA) were published in the peer-reviewed journal Addiction . It concluded that Gabasync is ineffective: "The PROMETA protocol, consisting of flumazenil, gabapentin and hydroxyzine, appears to be no more effective than placebo in reducing methamphetamine use, retaining patients in treatment or reducing methamphetamine craving." [134]
Barrons , in a November 2005 article entitled "Curb Your Cravings For This Stock", wrote "If the venture works out for patients and the investing public, it'll be a rare success for Peizer, who's promoted a series of disappointing small-cap medical or technology stocks ... since his days at Drexel". [135] Journalist Scott Pelley said to Peizer in 2007: "Depending and who you talk to, you're either a revolutionary or a snake oil salesman." [136] [135] 60 Minutes , NBC News , and The Dallas Morning News criticized Peizer after the company bypassed clinical studies and government approval when bringing to market Prometa; the addiction drug proved to be completely ineffective. [137] [138] [130] [139] Journalist Adam Feuerstein opined: "most of what Peizer says is dubious-sounding hype". [140]
The period from 2008 to 2018 saw a significant increase in the consumption of gabapentinoids. A study published in Nature Communications in 2023 highlights this trend, demonstrating a notable escalation in sales of gabapentinoids. The study, which analyzed healthcare data across 65 countries/ regions, found that the consumption rate of gabapentinoids had doubled over the decade, driven by their use in wide range of indications. [141]
Gabapentin was originally marketed under the brand name Neurontin. Since it became generic, it has been marketed worldwide using over 300 different brand names. [1] An extended-release formulation of gabapentin for once-daily administration was introduced in 2011, for postherpetic neuralgia under the brand name Gralise. [142]
In the US, Neurontin is marketed by Viatris after Upjohn was spun off from Pfizer. [143] [144] [145]
Parke-Davis developed a drug called pregabalin, which is related in structure to gabapentin, as a successor to gabapentin. [146] Another similar drug atagabalin has been unsuccessfully tried by Pfizer as a treatment for insomnia. [147] A prodrug form (gabapentin enacarbil) [148] was approved by the U.S. Food and Drug Administration (FDA).
![]() | The examples and perspective in this section deal primarily with US and do not represent a worldwide view of the subject.(August 2024) |
Gabapentin when taken in excess, can induce euphoria, a sense of calm, a cannabis-like high, improved sociability, and reduced alcohol or cocaine cravings. [149] [150] [151] Also known on the streets as "Gabbies", [152] gabapentin was reported in 2017 to be increasingly abused and misused for these euphoric effects. [153] [154] About 1 percent of the responders to an Internet poll and 22 percent of those attending addiction facilities had a history of abuse of gabapentin. [78] [155] Gabapentin misuse, toxicity, and use in suicide attempts among adults in the US increased from 2013 to 2017. [156]
After Kentucky's implementation of stricter legislation regarding opioid prescriptions in 2012, there was an increase in gabapentin-only and multi-drug use in 2012–2015. The majority of these cases were from overdose in suspected suicide attempts. These rates were also accompanied by increases in abuse and recreational use. [157]
Withdrawal symptoms, often resembling those of benzodiazepine withdrawal, play a role in the physical dependence some users experience. [79] Its misuse predominantly coincides with the usage of other CNS depressant drugs, namely opioids, benzodiazepines, and alcohol. [158]
In cats, gabapentin can be used as an analgesic in multi-modal pain management, [159] anxiety medication to reduce stress during travel or vet visits, [160] and anticonvulsant. [161]
Veterinarians may prescribe gabapentin as an anticonvulsant and pain reliever in dogs. [162] [161] It has beneficial effects for treating epilepsy, different kinds of pain (chronic, neuropathic, and post-operative pain), and anxiety, lip-licking behaviour, storm phobia, fear-based agression. [163] [164]
It is also used to treat chronic pain-associated nerve inflammation in horses and dogs. Side effects include tiredness and loss of coordination, but these effects generally go away within 24 hours of starting the medication. [162] [161]
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.
Ketoprofen is one of the propionic acid class of nonsteroidal anti-inflammatory drugs (NSAID) with analgesic and antipyretic effects. It acts by inhibiting the body's production of prostaglandin.
Anticonvulsants are a diverse group of pharmacological agents used in the treatment of epileptic seizures. Anticonvulsants are also increasingly being used in the treatment of bipolar disorder and borderline personality disorder, since many seem to act as mood stabilizers, and for the treatment of neuropathic pain. Anticonvulsants suppress the excessive rapid firing of neurons during seizures. Anticonvulsants also prevent the spread of the seizure within the brain.
Fibromyalgia is a medical syndrome which causes chronic widespread pain, accompanied by fatigue, waking unrefreshed, and cognitive symptoms. Other symptoms can include headaches, lower abdominal pain or cramps, and depression. People with fibromyalgia can also experience insomnia and a general hypersensitivity. The cause of fibromyalgia is unknown, but is believed to involve a combination of genetic and environmental factors. Environmental factors may include psychological stress, trauma, and certain infections. Since the pain appears to result from processes in the central nervous system, the condition is referred to as a "central sensitization syndrome".
Lamotrigine, sold under the brand name Lamictal among others, is a medication used to treat epilepsy and stabilize mood in bipolar disorder. For epilepsy, this includes focal seizures, tonic-clonic seizures, and seizures in Lennox-Gastaut syndrome. In bipolar disorder, lamotrigine has not been shown to reliably treat acute depression in any groups except for the severely depressed; but for patients with bipolar disorder who are not currently symptomatic, it appears to reduce the risk of future episodes of depression.
Depressants, colloquially known as "downers" or central nervous system (CNS) depressants, are drugs that lower neurotransmission levels, decrease the electrical activity of brain cells, or reduce arousal or stimulation in various areas of the brain. Some specific depressants do influence mood, either positively or negatively, but depressants often have no clear impact on mood. In contrast, stimulants, or "uppers", increase mental alertness, making stimulants the opposite drug class from depressants. Antidepressants are defined by their effect on mood, not on general brain activity, so they form an orthogonal category of drugs.
Duloxetine, sold under the brand name Cymbalta among others, is a medication used to treat major depressive disorder, generalized anxiety disorder, obsessive-compulsive disorder, fibromyalgia, neuropathic pain and central sensitization. It is taken by mouth.
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.
Baclofen, sold under the brand name Lioresal among others, is a medication used to treat muscle spasticity such as from a spinal cord injury or multiple sclerosis. It may also be used for hiccups and muscle spasms near the end of life, and off-label to treat alcohol use disorder or opioid withdrawal symptoms. It is taken orally or by intrathecal pump. It is also sometimes used transdermally in combination with gabapentin and clonidine prepared at a compounding pharmacy.
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.
Physical dependence is a physical condition caused by chronic use of a tolerance-forming drug, in which abrupt or gradual drug withdrawal causes unpleasant physical symptoms. Physical dependence can develop from low-dose therapeutic use of certain medications such as benzodiazepines, opioids, stimulants, antiepileptics and antidepressants, as well as the recreational misuse of drugs such as alcohol, opioids and benzodiazepines. The higher the dose used, the greater the duration of use, and the earlier age use began are predictive of worsened physical dependence and thus more severe withdrawal syndromes. Acute withdrawal syndromes can last days, weeks or months. Protracted withdrawal syndrome, also known as post-acute-withdrawal syndrome or "PAWS", is a low-grade continuation of some of the symptoms of acute withdrawal, typically in a remitting-relapsing pattern, often resulting in relapse and prolonged disability of a degree to preclude the possibility of lawful employment. Protracted withdrawal syndrome can last for months, years, or depending on individual factors, indefinitely. Protracted withdrawal syndrome is noted to be most often caused by benzodiazepines. To dispel the popular misassociation with addiction, physical dependence to medications is sometimes compared to dependence on insulin by persons with diabetes.
Tiagabine is an anticonvulsant medication produced by Cephalon that is used in the treatment of epilepsy. The drug is also used off-label in the treatment of anxiety disorders and panic disorder.
Pregabalin, sold under the brand name Lyrica among others, is an anticonvulsant, analgesic, and anxiolytic amino acid medication used to treat epilepsy, neuropathic pain, fibromyalgia, restless legs syndrome, opioid withdrawal, and generalized anxiety disorder (GAD). Pregabalin also has antiallodynic properties. Its use in epilepsy is as an add-on therapy for partial seizures. It is a gabapentinoid medication which are drugs that are derivatives of γ-aminobutyric acid (GABA), an inhibitory neurotransmitter. Pregabalin acts by inhibiting certain calcium channels. When used before surgery, it reduces pain but results in greater sedation and visual disturbances. It is taken by mouth.
Thiocolchicoside is a muscle relaxant with anti-inflammatory and analgesic effects. Its mechanism of action is unknown, but it is believed to be act via antagonism of nicotinic acetylcholine receptors (nAchRs). However, it also appears to be a competitive antagonist of GABAA and glycine receptors. As such, it has powerful convulsant activity and should not be used in seizure-prone individuals.
An orexigenic, or appetite stimulant, is a drug, hormone, or compound that increases appetite and may induce hyperphagia. This can be a medication or a naturally occurring neuropeptide hormone, such as ghrelin, orexin or neuropeptide Y, which increases hunger and therefore enhances food consumption. Usually appetite enhancement is considered an undesirable side effect of certain drugs as it leads to unwanted weight gain, but sometimes it can be beneficial and a drug may be prescribed solely for this purpose, especially when the patient is suffering from severe appetite loss or muscle wasting due to cystic fibrosis, anorexia, old age, cancer or AIDS. There are several widely used drugs which can cause a boost in appetite, including tricyclic antidepressants (TCAs), tetracyclic antidepressants, natural or synthetic cannabinoids, first-generation antihistamines, most antipsychotics and many steroid hormones. In the United States, no hormone or drug has currently been approved by the FDA specifically as an orexigenic, with the exception of Dronabinol, which received approval for HIV/AIDS-induced anorexia only.
4-Methylpregabalin is a drug developed by Pfizer and related to pregabalin, which similarly acts as an analgesic with effectiveness against difficult to treat "atypical" pain syndromes such as neuropathic pain. The effectiveness of pregabalin and its older relative gabapentin against pain syndromes of this kind has led to their widespread use, and these drugs have subsequently been found to be useful for many other medical applications, including as anticonvulsants, muscle relaxants, anxiolytics and mood stabilisers.
EMA401 is a drug under development for the treatment of peripheral neuropathic pain. Trials were discontinued in 2015, with new trials scheduled to begin March, 2018. It was initially established as a potential drug option for patients suffering pain caused by postherpetic neuralgia. It may also be useful for treating various types of chronic neuropathic pain EMA401 has shown efficacy in preclinical models of shingles, diabetes, osteoarthritis, HIV and chemotherapy. EMA401 is a competitive antagonist of angiotensin II type 2 receptor (AT2R) being developed by the Australian biotechnology company Spinifex Pharmaceuticals. EMA401 target angiotensin II type 2 receptors, which may have importance for painful sensitisation.
Gabapentinoids, also known as α2δ ligands, are a class of drugs that are derivatives of the inhibitory neurotransmitter gamma-Aminobutyric acid (GABA) which block α2δ subunit-containing voltage-dependent calcium channels (VDCCs). This site has been referred to as the gabapentin receptor, as it is the target of the drugs gabapentin and pregabalin.
Mirogabalin is a gabapentinoid medication developed by Daiichi Sankyo. Gabapentin and pregabalin are also members of this class. As a gabapentinoid, mirogabalin binds to the α2δ subunit of voltage-gated calcium channel, but with significantly higher potency than pregabalin. It has shown promising results in Phase II clinical trials for the treatment of diabetic peripheral neuropathic pain.
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.
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