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1. Gabapentin, Neurontin, Horizant, Gabarone
Gabapentin is a GABA analog. It was originally developed to treat epilepsy and currently is also used to relieve neuropathic pain. There are, however, concerns regarding the quality of the trials conducted for a number of conditions. It may be effective in reducing pain and spasticity in multiple sclerosis.
Gabapentin's most common side effects in adult patients include dizziness, fatigue, weight gain, drowsiness, and peripheral edema (swelling of extremities); these mainly occur at higher doses in the elderly. Also, in children 3 to 12 years of age, researchers observed susceptibility to mild-to-moderate mood swings, hostility, concentration problems, and hyperactivity. Though rare, the literature reports several cases of hepatotoxicity. Gabapentin should be used carefully in patients with renal impairment due to possible accumulation and toxicity. An increase in formation of adenocarcinomas was observed in rats during preclinical trials. However, the clinical significance of these results remains undetermined. Gabapentin is also known to induce pancreatic acinar cell carcinomas in rats through an unknown mechanism, perhaps by stimulation of DNA synthesis. These tumors did not affect the lifespan of the rats and did not metastasize.
Gabapentin has been associated with an increased risk of suicidal acts or violent deaths. In 2009 the U.S. Food and Drug Administration issued a warning of an increased risk of depression and suicidal thoughts and behaviors in patients taking gabapentin, along with other anticonvulsant drugs modifying the packaging insert to reflect this. In July 2009 the manufacturer of gabapentin (Pfizer) went to trial regarding the association between gabapentin and the increased risk of suicide. Drugs.com.
1. Holmøy T. Long-term effect of gabapentin in stiff limb syndrome: a case report. Eur Neurol. 2007;58(4):251-2. Epub 2007 Sep 12. Link to article
2. Todman D. Stiff-Person Syndrome (Moersch-Woltman Syndrome). The Internet Journal of Neurology. 2006 Volume 7 Number 1. Link to article
3. Murinson B. Stiff-person syndrome. Johns Hopkins.School of Medicine. Link to article
2. Gabapentin enacarbil, Regnit, Horizant
Gabapentin is a prodrug for the anticonvulsant and analgesic drug gabapentin. It was designed for increased oral bioavailability over gabapentin. Human trials showed it to produce extended release of gabapentin with almost twice the overall bioavailability, especially when taken with a fatty meal. Gabapentin enacarbil has passed human clinical trials for the treatment of restless legs syndrome and initial results have shown it to be well tolerated and reasonably effective. Gabapentin enacarbil was denied approval by the U.S. Food and Drug Administration (FDA) in February 2010, citing concerns about possible increased cancer risk shown by some animal studies. Similar concerns had been raised about gabapentin itself in the past, but were felt to be outweighed by its clinical utility as an anticonvulsant, whereas the treatment of restless legs syndrome was not seen to justify the same kind of risk. Drugs.com
3. Hopantenic acid, homopantothenic acid, Pantogam
Hopantenic acid is a central nervous system drug. Formulated as the calcium salt, it is used in the Russian Federation for a variety of neurological, psychological, and psychiatric conditions. Pantogam’s mechanism of action is due to a direct effect on GABA-β receptor-channel complex. The drug has neuroprotective and anticonvulsant effects. Pantogam increases the brain’s resistance to hypoxia and to the action of toxic substances. It stimulates the anabolic processes in neurons, possesses anticonvulsive action, and decreases motor excitability. It also increases mental and physical capacity for work by normalizing the GABA metabolism. Drugs.com.
Imagabalin is a drug which acts as a ligand for the α2δ subunit of the voltage-dependent calcium channel with some selectivity for the α2δ1 subunit over α2δ2. Under development by Pfizer as a pharmaceutical medication, it has demonstrated preclinical efficacy of anxiolytic, analgesic, hypnotic, and anticonvulsant-like activity and is currently in phase III clinical trials for the treatment of generalized anxiety disorder. Wikipedia.
5 Pregabalin, Lyrica
Pregabalin is an anticonvulsant drug used for neuropathic pain and as an adjunct therapy for partial seizures with or without secondary generalization in adults. It has also been found effective for generalized anxiety disorder and was designed as a more potent successor to gabapentin. Pregabalin exerts its acitivity by modulation of alpha-2-delta-subtype of neuronal calcium channels.
Like gabapentin, pregabalin binds to the α2δ (alpha-2-delta) subunit of the voltage-dependent calcium channel in the central nervous system. Pregabalin decreases the release of neurotransmitters including glutamate, norepinephrine, substance P, and calcitonin gene-related peptide. However, unlike anxiolytic compounds (e.g., benzodiazepines), which exert their therapeutic effects through binding to GABA-α, pregabalin neither binds directly to these receptors nor augments GABA-α currents or affects GABA metabolism. The half-life for pregabalin is 6.3 hours. Drugs.com
1. Squintani G, Bovi T, Ferigo L, et al. Efficacy of pregabalin in a case of stiff-person syndrome: clinical and neurophysiological evidence. J Neurol Sci. 2012 Mar 15;314(1-2):166-8. doi: 10.1016/j.jns.2011.10.023. Epub 2011 Nov 13. Link to article