Dopamine reuptake inhibitor
A dopamine reuptake inhibitor (DRI) is a type of drug which acts as a reuptake inhibitor of the monoamine neurotransmitter dopamine by blocking the action of the dopamine transporter (DAT). Reuptake inhibition is achieved when extracellular dopamine not absorbed by the postsynaptic neuron is blocked from re-entering the presynaptic neuron. This, in turn, leads to increased extracellular concentrations of dopamine and therefore an increase in dopaminergic neurotransmission.
DRIs are frequently used in the treatment of conditions like ADHD and narcolepsy on account of their psychostimulant effects and in the treatment of obesity due to their appetite suppressant properties. They have also been used as antidepressants in the treatment of mood disorders, but their use for this indication has been limited on account of their abuse potential and legal restrictions. Lack of dopamine reuptake and the increase in extracellular levels of dopamine have been linked to increased susceptibility to addictive behavior due to the increase in dopaminergic neurotransmission. The dopaminergic pathways are considered to be strong reward centers. In addition, many DRIs such as cocaine are drugs of abuse due to the rewarding effects evoked by elevated synaptic concentrations of dopamine in the brain.
Society and culture
History of use
Until the 1950s, dopamine was thought to be nothing but part of the biosynthesis of norepinephrine and epinephrine. It was not until dopamine was found in the brain in same levels as norepinephrine that it was considered that dopamine might have a biological role other than the synthesis of the catecholamines.
The following drugs have DRI action and have been or are used clinically specifically for this property: amineptine, dexmethylphenidate, difemetorex, fencamfamine, lefetamine, levophacetoperane, medifoxamine, mesocarb, methylphenidate, nomifensine, pipradrol, prolintane, and pyrovalerone. The following drugs are or have been used clinically and possess only weak DRI action, which may or may not be clinically-relevant: adrafinil, armodafinil, bupropion, mazindol, modafinil, nefazodone, sertraline, and sibutramine. The following drugs are or have been clinically used but only coincidentally have DRI properties: benzatropine, diphenylpyraline, etybenzatropine, ketamine, nefopam, pethidine (meperidine), and tripelennamine. And, while virtually all DRIs are abused recreationally, the following are a selection of some particularly notable ones: cocaine, ketamine, MDPV, naphyrone, and phencyclidine (PCP). Amphetamines, including amphetamine, methamphetamine, MDMA, cathinone, methcathinone, mephedrone, and methylone, are all DRIs as well, but are distinct in that they additionally behave, and often much more potently, as dopamine releasing agents (DRAs).
Recently, the FDA-approved wakefulness-promoting agent modafinil and its analogues (e.g., adrafinil, armodafinil, fluorenol), which are approved to treat narcolepsy and shift work sleep disorder, were found to act as weak (micromolar) DRIs. However, this property has been found to not correlate with their wakefulness-promoting effects, suggesting that it is too weak to be of clinical significance and that these drugs promote wakefulness via some other mechanism.
DRIs have been explored as potential antiaddictive agents because of their ability to replace reward received from other drugs. DRIs have been successfully used to serve as nicotine replacements in cases of smoking addictions well as methadone replacements in the case of heroin addiction. DRIs have been explored as potential substitutes for cocaine addiction, and have been shown to alleviate cravings and self-administration.
Monoamine reuptake inhibitors, including DRIs, have also been shown to be effective as therapy for food intake and appetite control for obese subjects. However, most marketed drugs for this purpose have been withdrawn or discontinued due to adverse side effects such as increase in blood pressure and high abuse potential.
List of DRIs
Many DRIs exist, an assortment which are listed below. Note that only DRIs which are selective for the DAT over the other monoamine transporters (MATs) are listed below. For a list of DRIs that act at multiple MATs, see other monoamine reuptake inhibitor pages such as NDRI and SNDRI.
Selective dopamine reuptake inhibitors
- Altropane (O-587)
- Amfonelic acid (WIN 25978)
- Amineptine (has a reasonable degree of selectivity for dopamine over norepinephrine reuptake inhibition)
- BTCP (GK-13)
- Difluoropine (O-620)
- Iometopane (β-CIT, RTI-55)
- Vanoxerine (GBR-12909)
DRIs with activity at other sites
- Adrafinil (weak)
- Armodafinil (weak)
- Benztropine (also muscarinic antagonist)
- Fluorenol (extremely weak)
- Medifoxamine (relatively weak)
- Metaphit (irreversible; depletes dopamine)
- Modafinil (weak)
- Chaenomeles speciosa (Flowering Quince)
- Oroxylin A (found in Oroxylum indicum and Scutellaria baicalensis (Skullcap))
- Kavain and desmethoxyyangonin (possibly) (found in Piper methysticum (Kava))
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