Surveillance of First-Generation H1-Antihistamine Use for Older Patients with Dementia in Japan: A Retrospective Cohort Study

Classics in Chemical Neuroscience: Deliriant Antihistaminic Drugs

Antihistaminic drugs are widely used clinically and have long been primarily known for their use to treat severe allergic conditions caused by histamine release. Antihistaminic drugs also exert central nervous system (CNS) effects, acting as anxiolytics, hypnotics, and neuroleptics. However, these drugs also have multiple serious neuropharmacological side-effects, inducing delirium, hyperarousal, disorganized behavior, and hallucinations. Due to their robust CNS effects, antihistamines are also increasingly abused, with occasional overdoses and life-threatening toxicity. Here, we discuss chemical and neuropharmacological aspects of antihistaminic drugs in both human and animal (experimental) models and outline their current societal and mental health importance as neuroactive substances.

The Usage of Histamine Type 1 Receptor Antagonist and Risk of Dementia in the Elderly: A Nationwide Cohort Study

Background

The histamine type 1 receptor antagonist (H1RA) has been commonly used. This study aimed to examine the association between the usage of H1RA and the risk of dementia.

Methods

A total of 8,986 H1RA users aged ≥50 and 26,958 controls matched a ratio of 1:3 for age, sex, and comorbidity, were selected between January 1, and December 31, 2000, from Taiwan’s National Health Insurance Research Database. Fine and Gray’s survival analysis (competing with mortality) was used to compare the risk of developing dementia during a 15-year follow-up period (2000–2015).

Results

In general, the H1RA usage was not significantly associated with dementia (adjusted subdistribution hazard ratio [SHR] = 1.025, 95% confidence interval [CI] = 0.883–1.297, p = 0.274) for the H1RA cohort. However, a differential risk was found among the groups at risk. The patients with the usage of H1RA aged ≥65 years (adjusted SHR: 1.782, 95% CI = 1.368–2.168, p < 0.001) were associated with a higher risk of dementia, in comparison to the control groups. Furthermore, the patients with the usage of H1RA that were male, or had more comorbidities, were also associated with an increased risk of dementia.

Conclusion

The usage of H1RA was associated with the risk of developing dementia in the patients aged ≥ 65 years.

Using Patient Profiles To Guide The Choice Of Antihistamines In The Primary Care Setting In Malaysia: Expert Consensus And Recommendations

H1-antihistamines are recognized to be effective for conditions such as allergic rhinitis and chronic spontaneous urticaria. However, management of such conditions in the real-world primary care setting may be challenging due to diverse patient-specific considerations, the wide range of antihistamines available, choice of other treatment modalities, and the complexity of interpreting specialist treatment algorithms. Despite regular updates to international guidelines, regional/national surveys of healthcare professionals show a clear gap between guidelines and real-world practice, particularly at the primary care level. This article thus presents the consensus opinion of experts from relevant specialties in Malaysia - allergology, pediatrics, otorhinolaryngology, and dermtology - on harmonizing the use and choice of antihistamines in primary care. Patient profiling is recommended as a tool to guide primary care practitioners in prescribing the appropriate antihistamine for each patient. Patient profiling is a three-step approach that involves 1) identifying the individual's needs; 2) reviewing patient-specific considerations; and 3) monitoring treatment response and referral to specialists in more severe or difficult-to-treat cases. Concurrently, guidelct 3ines should be reviewed and updated periodically to include recommendations that are easily actionable for primary care practitioners.