Misuse and dependence of dimenhydrinate: A mixed studies systematic review

Chronic high-dose dimenhydrinate use contributing to early multifactorial cognitive impairment

Dimenhydrinate is an over-the-counter antihistaminergic medication with anticholinergic properties used to treat nausea or motion sickness worldwide. There is a well-established correlation between the use of anticholinergic medications and dementia, however, it is unclear if a causal role exists. We report a case of minor neurocognitive disorder in a woman in her 40s with several years of high-dose daily dimenhydrinate abuse who subsequently developed significant delusional beliefs. Her clinical presentation was confounded by numerous other factors that could have impacted her cognition, such as a longstanding presumed learning disability, ankylosing spondylitis with adalimumab treatment, extensive cannabis use or potential development of a primary psychotic disorder. Her workup was within normal limits, and she has not responded to first-line antipsychotic medications to date. This case report adds to the growing evidence supporting concerns about potentially irreversible cognitive deficits in chronic misuse of anticholinergic agents, an association previously observed only in the elderly population.

Clinical relevance of inherited genetic differences in human tryptases: Hereditary alpha-tryptasemia and beyond

OBJECTIVE

To describe our current understanding of hereditary α-tryptasemia (HαT), how HαT fits into the evolutionary context of tryptases and contemporary framework of mast cell-associated disorders, and to discuss the future clinical and therapeutic landscape for symptomatic individuals with HαT.

DATA SOURCES

Primary peer-reviewed literature.

STUDY SELECTIONS

Basic, clinical, and translational studies describing tryptase gene composition, generation, secretion, and elevation and the associated clinical impacts of HαT and treatment of such individuals were reviewed.

RESULTS

HαT is a common autosomal dominant genetic trait caused by increased TPSAB1 copy number encoding α-tryptase. Approximately 1 in 20 White individuals have HαT, making it by far the most common cause for elevated basal serum tryptase levels. Although many individuals with HαT may not manifest associated symptoms, the prevalence of HαT is increased in patients with clonal and nonclonal mast cell-associated disorders wherein it is linked to more prevalent and/or severe anaphylaxis and increased mast cell mediator-associated symptoms. Increased generation of mature α/β-tryptase heterotetramers, and their unique physiochemical properties, may be responsible for some of these clinical findings.

CONCLUSION

HαT is a common modifier of mast cell-associated disorders and reactions. Nevertheless, whether HαT may be an independent cause of clinical phenotypes with which it has been associated remains unproven. Correct identification of HαT is critical to accurate interpretation of serum tryptase levels in the clinical evaluation of patients. Beyond HαT, we foresee tryptase genotyping as an important parameter in the standard workup of patients with mast cell-associated disorders and development of therapeutic modalities targeting these patients and associated clinical phenotypes.