Dopamine dysregulation syndrome | |
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Two-dimensional skeletal formula of the dopamine molecule. Dopamine receptor agonists mediate the development of DDS. |
Dopamine dysregulation syndrome (DDS) is a dysfunction of the reward system observed in some individuals taking dopaminergic medications for an extended length of time. It typically occurs in people with Parkinson's disease (PD) who have taken dopamine agonist medications for an extended period of time. It is characterized by problems such as addiction to medication, gambling, or sexual behavior. [1]
The most common symptom is craving for dopaminergic medication. However other behavioral symptoms can appear independently of craving or co-occur with it. [2] Craving is an intense impulse of the subject to obtain medication even in the absence of symptoms that indicate its intake. [2] To fulfill this need the person will self-administer extra doses. When self-administration is not possible, aggressive outbursts or the use of strategies such as symptom simulation or bribery to access additional medication can also appear. [2]
Hypomania, manifesting with feelings of euphoria, omnipotence, or grandiosity, are prone to appear in those moments when medication effects are maximum; dysphoria, characterized by sadness, psychomotor slowing, fatigue or apathy are typical with dopamine replacement therapy (DRT) withdrawal. [2] Different impulse control disorders have been described including gambling, compulsive shopping, eating disorders and hypersexuality. [2] Behavioral disturbances, most commonly aggressive tendencies, are the norm. Psychosis is also common. [2]
Parkinson's disease is a common neurological disorder characterized by a degeneration of dopamine neurons in the substantia nigra and a loss of dopamine in the putamen. It is described as a motor disease, but it also produces cognitive and behavioral symptoms. The most common treatment is dopamine replacement therapy, which consists in the administration of levodopa (L-Dopa) or dopamine agonists (such as pramipexole or ropinirole) to patients. Dopamine replacement therapy is well known to improve motor symptoms but its effects in cognitive and behavioral symptoms are more complex. [3] Dopamine has been related to the normal learning of stimuli with behavioral and motivational significance, attention, and most importantly the reward system. [4] In accordance with the role of dopamine in reward processing, addictive drugs stimulate dopamine release. [4] Although the exact mechanism has yet to be elucidated, the role of dopamine in the reward system and addiction has been proposed as the origin of DDS. [4] Models of addiction have been used to explain how dopamine replacement therapy produces DDS. [2] One of these models of addiction proposes that over the usage course of a drug there is a habituation to the rewarding effects that it produces at the initial stages. This habituation is thought to be dopamine mediated. With long-term administration of L-dopa the reward system gets used to it and needs higher quantities. As the user increases drug intake there is a loss of dopaminergic receptors in the striatum which acts in addition to an impairment in goal-direction mental functions to produce an enhancement of sensitization to dopamine therapy. The behavioral and mood symptoms of the syndrome are produced by the dopamine overdose. [4]
Diagnosis of the syndrome is clinical since there are no laboratory tests to confirm it. For diagnosis a person with documented responsiveness to medication has to increase medication intake beyond dosage needed to relieve their parkinsonian symptoms in a pathological addiction-like pattern. A current mood disorder (depression, anxiety, hypomanic state or euphoria), behavioral disorder (excessive gambling, shopping or sexual tendency, aggression, or social isolation) or an altered perception about the effect of medication also have to be present. [5] A questionnaire on the typical symptoms of DDS has also been developed and can help in the diagnosis process. [6]
The main prevention measure proposed is the prescription of the lowest possible dose of dopamine replacement therapy to individuals at risk. [4] The minimization of the use of dopamine agonists, and of short duration formulations of L-Dopa can also decrease risk of the syndrome. [4]
First choice management measure consists in the enforcement of a dopaminergic drug dosage reduction. If this decrease is maintained, dysregulation syndrome features soon decrease. [4] Cessation of dopamine agonists therapy may also be of use. [7] Some behavioral characteristics may respond to psychotherapy; and social support is important to control risk factors. In some cases antipsychotic drugs may also be of use in the presence of psychosis, aggression, gambling or hypersexuality. [4]
Based upon five case reports, [8] [9] valproic acid may have efficacy in controlling the symptoms of levodopa-induced DDS that arise from the use of levodopa for the treatment of Parkinson's disease. [10] [11] [12]
DDS is not common among PD patients. Prevalence may be around 4%. [1] [5] Its prevalence is higher among males with an early onset of the disease. [2] Previous substance abuse such as heavy drinking or drug intake seems to be the main risk factor along with a history of affective disorder. [2]
PD was first formally described in 1817; [13] however, L-dopa did not enter clinical practice until almost 1970. [14] [15] In these initial works there were already reports of neuropsychiatric complications. [15] During the following decades cases featuring DDS symptoms in relation to dopamine therapy such as hypersexuality, gambling or punding, appeared. [16] [17] [18] DDS was first described as a syndrome in the year 2000. [19] Three years later the first review articles on the syndrome were written, showing an increasing awareness of the DDS importance. [1] [4] [2] Diagnostic criteria were proposed in 2005. [5]
The substantia nigra (SN) is a basal ganglia structure located in the midbrain that plays an important role in reward and movement. Substantia nigra is Latin for "black substance", reflecting the fact that parts of the substantia nigra appear darker than neighboring areas due to high levels of neuromelanin in dopaminergic neurons. Parkinson's disease is characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta.
Dopamine is a neuromodulatory molecule that plays several important roles in cells. It is an organic chemical of the catecholamine and phenethylamine families. Dopamine constitutes about 80% of the catecholamine content in the brain. It is an amine synthesized by removing a carboxyl group from a molecule of its precursor chemical, L-DOPA, which is synthesized in the brain and kidneys. Dopamine is also synthesized in plants and most animals. In the brain, dopamine functions as a neurotransmitter—a chemical released by neurons to send signals to other nerve cells. Neurotransmitters are synthesized in specific regions of the brain, but affect many regions systemically. The brain includes several distinct dopamine pathways, one of which plays a major role in the motivational component of reward-motivated behavior. The anticipation of most types of rewards increases the level of dopamine in the brain, and many addictive drugs increase dopamine release or block its reuptake into neurons following release. Other brain dopamine pathways are involved in motor control and in controlling the release of various hormones. These pathways and cell groups form a dopamine system which is neuromodulatory.
Hypersexuality is a term used for a presumed mental disorder causing people to engage in or think about sex to a point of distress or impairment. It is controversial whether it should be included as a clinical diagnosis used by mental healthcare professionals. Nymphomania and satyriasis were terms previously used for the condition in women and men, respectively.
Restless legs syndrome (RLS), also known as Willis–Ekbom disease (WED), is generally a long-term disorder that causes a strong urge to move one's legs. There is often an unpleasant feeling in the legs that improves somewhat by moving them. This is often described as aching, tingling, or crawling in nature. Occasionally, arms may also be affected. The feelings generally happen when at rest and therefore can make it hard to sleep. Due to the disturbance in sleep, people with RLS may be sleepy during the day, have low energy, and feel irritable or depressed. Additionally, many have limb twitching during sleep, a condition known as periodic limb movement disorder. RLS is not the same as habitual foot-tapping or leg-rocking.
Dopamine receptors are a class of G protein-coupled receptors that are prominent in the vertebrate central nervous system (CNS). Dopamine receptors activate different effectors through not only G-protein coupling, but also signaling through different protein interactions. The neurotransmitter dopamine is the primary endogenous ligand for dopamine receptors.
l-DOPA, also known as levodopa and l-3,4-dihydroxyphenylalanine, is made and used as part of the normal biology of some plants and animals, including humans. Humans, as well as a portion of the other animals that utilize l-DOPA, make it via biosynthesis from the amino acid l-tyrosine. l-DOPA is the precursor to the neurotransmitters dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline), which are collectively known as catecholamines. Furthermore, l-DOPA itself mediates neurotrophic factor release by the brain and CNS. l-DOPA can be manufactured and in its pure form is sold as a psychoactive drug with the INN levodopa; trade names include Sinemet, Pharmacopa, Atamet, and Stalevo. As a drug, it is used in the clinical treatment of Parkinson's disease and dopamine-responsive dystonia.
Dyskinesia refers to a category of movement disorders that are characterized by involuntary muscle movements, including movements similar to tics or chorea and diminished voluntary movements. Dyskinesia can be anything from a slight tremor of the hands to an uncontrollable movement of the upper body or lower extremities. Discoordination can also occur internally especially with the respiratory muscles and it often goes unrecognized. Dyskinesia is a symptom of several medical disorders that are distinguished by their underlying cause.
Dopaminergic means "related to dopamine" (literally, "working on dopamine"), dopamine being a common neurotransmitter. Dopaminergic substances or actions increase dopamine-related activity in the brain. Dopaminergic brain pathways facilitate dopamine-related activity. For example, certain proteins such as the dopamine transporter (DAT), vesicular monoamine transporter 2 (VMAT2), and dopamine receptors can be classified as dopaminergic, and neurons that synthesize or contain dopamine and synapses with dopamine receptors in them may also be labeled as dopaminergic. Enzymes that regulate the biosynthesis or metabolism of dopamine such as aromatic L-amino acid decarboxylase or DOPA decarboxylase, monoamine oxidase (MAO), and catechol O-methyl transferase (COMT) may be referred to as dopaminergic as well. Also, any endogenous or exogenous chemical substance that acts to affect dopamine receptors or dopamine release through indirect actions (for example, on neurons that synapse onto neurons that release dopamine or express dopamine receptors) can also be said to have dopaminergic effects, two prominent examples being opioids, which enhance dopamine release indirectly in the reward pathways, and some substituted amphetamines, which enhance dopamine release directly by binding to and inhibiting VMAT2.
Ropinirole, sold under the brand name Requip among others, is a medication used to treat Parkinson's disease (PD) and restless legs syndrome (RLS). In PD the dose needs to be adjusted to the effect and treatment should not be suddenly stopped. It is taken by mouth.
Punding is compulsive performance of repetitive, mechanical tasks, such as assembling and disassembling, collecting, or sorting objects. It can also apply to digital objects, such as computer files and data. The term was originally coined to describe complex, prolonged, purposeless, and stereotyped behaviour in phenmetrazine and chronic amphetamine users, by Swedish forensic psychiatrist G. Rylander, in 1968. It was later described in Parkinson's disease, but mainly in cases of patients being treated with dopaminergic drugs. It has also been described in methamphetamine and cocaine users, as well as in some patients with gambling addictions, and hypersexuality.
Pramipexole, sold under the brand Mirapex among others, is medication used to treat Parkinson's disease (PD) and restless legs syndrome (RLS). In Parkinson's disease it may be used alone or together with levodopa. It is taken by mouth. Pramipexole is a dopamine agonist of the non-ergoline class.
A dopamine agonist(DA) is a compound that activates dopamine receptors. There are two families of dopamine receptors, D2-like and D1-like, and they are all G protein-coupled receptors. D1- and D5-receptors belong to the D1-like family and the D2-like family includes D2, D3 and D4 receptors. Dopamine agonists are primarily used in the treatment of Parkinson's disease, and to a lesser extent, in hyperprolactinemia and restless legs syndrome. They are also used off-label in the treatment of clinical depression. The use of dopamine agonists is associated with impulse control disorders and dopamine agonist withdrawal syndrome (DAWS).
In the management of Parkinson's disease, due to the chronic nature of Parkinson's disease (PD), a broad-based program is needed that includes patient and family education, support-group services, general wellness maintenance, exercise, and nutrition. At present, no cure for the disease is known, but medications or surgery can provide relief from the symptoms.
Dihydroergocryptine (DHEC), sold under the brand names Almirid and Cripar among others, is a dopamine agonist of the ergoline group that is used as an antiparkinson agent in the treatment of Parkinson's disease. It is taken by mouth.
Parkinson's disease (PD), or simply Parkinson's, is a chronic degenerative disorder of the central nervous system that affects both the motor system and non-motor systems. The symptoms usually emerge slowly, and as the disease worsens, non-motor symptoms become more common. Early symptoms are tremor, rigidity, slowness of movement, and difficulty with walking. Problems may also arise with cognition, behaviour, sleep, and sensory systems. Parkinson's disease dementia becomes common in advanced stages of the disease.
Signs and symptoms of Parkinson's disease are varied. Parkinson's disease affects movement, producing motor symptoms. Non-motor symptoms, which include dysautonomia, cognitive and neurobehavioral problems, and sensory and sleep difficulties, are also common. When other diseases mimic Parkinson's disease, they are categorized as parkinsonism.
Levodopa-induced dyskinesia (LID) is a form of dyskinesia associated with levodopa (l-DOPA), used to treat Parkinson's disease. It often involves hyperkinetic movements, including chorea, dystonia, and athetosis.
Kufor–Rakeb syndrome (KRS) is an autosomal recessive disorder of juvenile onset also known as Parkinson disease-9 (PARK9). It is named after Kufr Rakeb in Irbid, Jordan. Kufor–Rakeb syndrome was first identified in this region in Jordan with a Jordanian couple's 5 children who had rigidity, mask-like face, and bradykinesia. The disease was first described in 1994 by Najim Al-Din et al. The OMIM number is 606693.
Gene therapy in Parkinson's disease consists of the creation of new cells that produce a specific neurotransmitter (dopamine), protect the neural system, or the modification of genes that are related to the disease. Then these cells are transplanted to a patient with the disease. There are different kinds of treatments that focus on reducing the symptoms of the disease but currently there is no cure.
Dopamine therapy is the regulation of levels of the neurotransmitter dopamine through the use of either agonists, or antagonists; and has been used in the treatment of disorders characterized by a dopamine imbalance. Dopamine replacement therapy (DRT) is an effective treatment for patients with decreased levels of dopamine. Often dopamine agonists, compounds that activate dopamine receptors in the absence of that receptor's physiological ligand, the neurotransmitter dopamine, are used in this therapy. DRT has been shown to reduce symptoms and increase lifespan for patients with Parkinson's disease. Dopamine regulation plays a critical role in human mental and physical health. The neurons that contain the neurotransmitter are clustered in the midbrain region in an area called the substantia nigra. In Parkinson's patients, the death of dopamine-transmitting neurons in this area leads to abnormal nerve-firing patterns that cause motor problems. Research in patients with schizophrenia indicates abnormalities in dopamine receptor structure and function.