For this reason levodopa is usually administered in combination with a DOPA decarboxylase inhibitor (DDCI), in this case carbidopa, which is very polar (and charged at physiologic pH) and cannot cross the blood brain barrier, however prevents peripheral conversion of levodopa to dopamine and thereby reduces the unwanted peripheral side effects of levodopa. Use of carbidopa also increases the quantity of levodopa in the bloodstream that is available to enter the brain. History
In 1960 the Austrian biochemist Oleh Hornykiewicz, while at the University of Vienna, examined results of autopsies of patients who had died with Parkinsons disease. He suggested that the disease was associated with, or caused by, a reduction in the levels of dopamine in the basal ganglia of the brain. Since dopamine itself did not enter the brain, he tried treating twenty patients with a racemic mixture of dihydroxyphenylalanine (DOPA), which could enter the brain and be converted there to dopamine by the action of DOPA decarboxylase. His results were positive, as were those of another trial in Montreal run by André Barbeau. Unfortunately, other investigators were unable to replicate these early results, and the use of DOPA remained in question until 1967, when George Cotzias at the Brookhaven National Laboratories in Upton, New York, used megadoses of DOPA, up to 16 grams per day.
Prevalence studies suggest that ICDs occur in 13.6–36.0% of Parkinsons patients exhibited at least one form of ICD. There is a significant co-occurrence of pathological gambling and personality disorder, and is suggested to be caused partly by their common "genetic vulnerability". The degree of heritability to ICD is similar to other psychiatric disorders including substance use disorder. There has also been found a genetic factor to the development of ICD just as there is for substance use disorder. The risk for subclinical PG in a population is accounted for by the risk of alcohol dependence by about 12–20% genetic and 3–8% environmental factors. There is a high rate of co-morbidity between ADHD and other impulse-control disorders. Mechanism
Dysfunction of the striatum may prove to be the link between OCD, ICD and SUD. According to research, the impulsiveness that occurs in the later stages of OCD is caused by progressive dysfunction of the ventral striatal circuit. Whereas in case of ICD and SUD, the increased dysfunction of dorsal striatal circuit increases the "ICD and SUD behaviours that are driven by the compulsive processes". OCD and ICD have traditionally been viewed as two very different disorders, the former one is generally driven by the desire to avoid harm whereas the latter one driven "by reward-seeking behaviour". Still, there are certain behaviors similar in both, for example the compulsive actions of ICD patients and the behavior of reward-seeking (for example hoarding) in OCD patients. Treatment
Impulse-control disorders have two treatment options: psychosocial and pharmacological.