Dimenhydrinate Dependence in Patient with Previous History of Psychiatric Disorder
A 33-years-old woman presented with feelings of nervousness, irritability, generalized anxiety, insomnia, depressed mood,and persistent suicidal ideation. Concomitantly, she reported relief of these symptoms when using DMH. Currently in our Center for Psychosocial Care, she received a Borderline Personality Disorder diagnosis besides tobacco and DMH dependence.
Smoker since she was 12 years, her history was remarkablefor the initial use of DMH at the age of 16 years when threetablets were usual to avoid nausea during often bus travels. At the age of 26 years, she started the daily and increasing use ofDMH, culminating to the use of 40 tablets/day of DMH (4 g /day = 10 times the therapeutic dose). The patient also relatedharmful use of alcohol since 14 years old, besides experimentaluse of marijuana, volatile solvents and inhaled cocaine inadolescence. Further, lots of medications, including benzodiazepines,were taken though an accurate diagnosis has never been reached.
She presents several signs of self-mutilation in the forearmsand at least three hospital admissions due to exogenous intoxication with alcohol and medications. After she got pregnant,stopped with harmful use of alcohol and any other medication,however, maintained – to this day – the use of 4 g of DMH / dayassociated with tobacco (currently, the child is at 4 months oflife; born with Interventrivular Communication which evolvedbenignly). Besides the evident tolerance, reducing or stoppingthe consumption of DMH do cause great craving, irritabilityand ‘explosive’ behavior. The patient is now admitted for detoxificationand stabilization of the psychiatric framework.
The patient presented history of Borderline Personality Disorder and drug abuse, that probably contributed to the dimenhydrinate dependence related here.
Drug dependence is a chronic and relapsing disorder characterized by compulsive use despite negative consequences . Alcohol, tobacco and other illicit drugs are well known as addictive substances. However, cases involving medicine dependence are rarely reported. This one involving DMH, a low cost medicine that can be available without medical prescription, has called our attention. Most likely, low cost and easy access to this medication added to the fact of being an unusual dependence may lead to lower rates of reported DMH dependence .
DMH at therapeutic doses has antiemetic, nauseous and anti-vertiginous action attributed to the H1 receptors antagonism in the vestibular system . On the other hand, it was observed that peripheral administration of antihistamines increases dopamine levels in the nucleus Accumbens due to both increased release  and inhibition of dopamine reuptake  that could explain its rewarding effect in the brain. Additionally, animal studies show that the action of antihistamines in the inhibition of serotonin and noradrenalin reuptake is related to their antidepressant effects[5–8].
Together with these evidences in the brain reward system, we suggest that the history of psychiatric disorder contributed as a risk factor for the development of DMH dependence in this patient.
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