Memory and cognitive impairments in a case of long-term trihexyphenidyl abuse

Trihexyphenidyl increases delta activity in non-rapid eye movement sleep without impairing cognitive function in rodent models

Both human and rodent studies suggest the link between non-rapid eye movement (NREM) sleep and cognition. Recent study indicated that selective activation of cholinergic neurons in basal forebrain inhibits electroencephalogram (EEG) delta power and shortens NREM sleep. In the current study, we aimed to test the pharmacological effect of trihexyphenidyl (THP), a selective muscarinic M1 receptor antagonist, on EEG power spectra and sleep with or without the selective activation of basal forebrain cholinergic neurons. THP (1, 2, and 3 mg/kg) was administrated intraperitoneally in natural sleep phase. Basal forebrain cholinergic neurons expressing modified G protein-coupled muscarinic receptors (hM3Dq) were activated by intraperitoneal injection of clozapine-N-oxide in ChAT-IRES-Cre mice. EEG and electromyogram (EMG) signals were recorded in freely moving mice to analyze EEG power spectrum and sleep hypnogram. Y-maze and novel object recognition tests were used for testing cognition. THP 1 mg/kg significantly increased EEG delta power and facilitated NREM sleep in wildtype mice, while THP 3 mg/kg was required in ChAT-IRES-Cre mice treated with clozapine-N-oxide. THP with dosage up to 8 mg/kg did not induce cognitive impairments in wildtype mice. EEG delta power of NREM sleep is often used as an indicator of sleep depth or sleep quality, which tightly link with sleep-dependent cognition. Taken together, the data collected from rodents hinted that, THP could possibly be used as the NREM sleep facilitator in humans.

Misuse of Anticholinergic Medications: A Systematic Review

(1) Background: Over the last decade, misuse and diversion of medications has appeared to be increasingly concerning phenomena, including a range of different molecules. As current knowledge on the abuse of centrally acting anticholinergics is limited, the aim of the present study is to review the relevant published data, focusing on the following molecules: benztropine, biperiden, scopolamine, orphenadrine, and benzhexol/trihexyphenidyl (THP). (2) Methods: A systematic literature review was carried out using Pubmed, Scopus, and Web of Science databases following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Research methods were registered on PROSPERO (CRD42021257293). (3) Results: A total of 48 articles, including case reports, surveys, and retrospective case series analyses, were included. Most articles focused on benzhexol/THP (n = 25), and benztropine (n = 4). The routes of administration were mostly oral, and macrodoses together concomitant illicit drugs, e.g., cocaine, have been recorded. Toxidromes included both physical (e.g., tachycardia, tachypnoea, dilatated pupils, dry skin, urinary retention, ataxia, etc.) and psychiatric symptoms (e.g., anxiety, agitation, delirium, etc.). Fatal outcomes were very rare but reported. (4) Conclusion: Results from the present study show that anticholinergic misusing issues are both widespread worldwide and popular. Considering the potential adverse effects associated, healthcare professionals should be vigilant and monitor eventual misusing issues.

Long-term trihexyphenidyl exposure alters neuroimmune response and inflammation in aging rat: relevance to age and Alzheimer's disease

BACKGROUND

Clinical studies have shown an association between long-term anticholinergic (AC) drug exposure and Alzheimer's disease (AD) pathogenesis, which has been primarily investigated in Parkinson's disease (PD). However, long-term AC exposure as a risk factor for developing neurodegenerative disorders and the exact mechanisms and potential for disease progression remain unclear. Here, we have addressed the issue using trihexyphenidyl (THP), a commonly used AC drug in PD patients, to determine if THP can accelerate AD-like neurodegenerative progression and study potential mechanisms involved.

METHODS

Male Sprague-Dawley rats (SD) were intraperitoneally injected with THP (0.3 and 1.0 mg/kg) or normal saline (NS) for 7 months. Alterations in cognitive and behavioral performance were assessed using the Morris water maze (MWM) and open field tests. After behavior tests, whole genome oligo microarrays, quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR), immunohistochemistry, and immunofluorescence-confocal were used to investigate the global mechanisms underlying THP-induced neuropathology with aging.

RESULTS

Compared with NS controls, the MWM test results showed that THP-treated rats exhibited significantly extended mean latencies during the initial 3 months of testing; however, this behavioral deficit was restored between the fourth and sixth month of MWM testing. The same tendencies were confirmed by MWM probe and open field tests. Gene microarray analysis identified 68 (47 %) upregulated and 176 (53 %) downregulated genes in the "THP-aging" vs. "NS-aging" group. The most significant populations of genes downregulated by THP were the immune response-, antigen processing and presentation-, and major histocompatibility complex (MHC)-related genes, as validated by qRT-PCR. The decreased expression of MHC class I in THP-treated aging brains was confirmed by confocal analysis. Notably, long-term THP treatment primed hippocampal and cortical microglia to undergo an inflammatory phenotypic switch, causing microgliosis and microglia activation, which were positively accompanied by pathological misfolded tau lesions.

CONCLUSIONS

Our findings suggest that immune response and neuroinflammation represent a pivotal mechanism in THP-induced AD-like neuropathology processes with long-term exposure to AC drugs.

Benzhexol-dependence resulting from self-medication for intermittent explosive disorder

Objective. Recent observations in Iraq during the period of sanction suggest the existence of benzhexol prescribing linked to its calming effects on explosive behaviours. This inspired our group to research the existence of this practice and the characteristics of those involved in it. Method. All patients from the psychiatric service in Merjan Hospital, Al Hilla City, Babylon Governate, Iraq, who had a prescription for benzhexol between January 1991 and December 2000, were identified. All participants received their diagnosis based on the clinical criteria of the DSM-IV, after taking a comprehensive medical and psychiatric history, mental state examination and collateral information from family members. The patients were evaluated by the same qualified consultant psychiatrist at the initial assessment and all through the period of follow-up. Results. In the 10-year period under study, 354 patients were prescribed benzhexol. A total of 190 patients diagnosed as intermittent explosive disorder (IED) and 164 suffering from severe mental disorders or personality disorders were excluded from the study. The average age of the IED group was 29.5 years. On direct questioning, the main reason patients gave most frequently for using benzhexol was to control the aggressive outbursts (N=92, 48.4), to get high (N=49, 25.8), to relax (N=26, 13.7), to get rid of boredom (N=23, 12.1). In total, the whole group were prescribed benzhexol, at an average dose of 12.5 mg/day (range 2-20 mg/day). At the time of final assessment the mean dose of prescribed benzhexol had fallen slightly to 12 mg/day (2-20 mg/day), with 10 patients being benzhexol free. Of the 190, three patients had a diagnosis of obsessive compulsive disorders, 36 patients had a diagnosis of benzodiazepines dependence, and a further five had a diagnosis of alcohol dependency syndrome. Eighty percent felt satisfied with the effect of the drug and 95 were not motivated to stop it. Conclusions. There are a significant number of patients who are routinely prescribed benzhexol as a replacement therapy. The main original reason for starting it is to control outbursts and improves their reaction to stress situations. This growing issue raises the need for awareness, by both public and medical practitioners, of the potential adverse effects of benzhexol and its untoward consequences.

Increased mental slowing associated with the APOE epsilon4 allele after trihexyphenidyl oral anticholinergic challenge in healthy elderly

OBJECTIVES

The objectives of this study were to examine the relationship between APOE epsilon4 and subjective effects of trihexyphenidyl on measures reflecting sedation and confusion and to investigate the relationship between trihexyphenidyl-induced subjective effects and objective memory performance.

METHODS

This study comprised 24 cognitively intact, health elderly adults (12 APOE epsilon4 carriers) at an outpatient geriatric psychiatry research clinic. This was a randomized, double blind, placebo-controlled, three-way, crossover experimental design. All participants received 1.0 mg or 2.0 mg trihexyphenidyl or placebo administered in counterbalanced sequences over a period of three consecutive weeks. Bond and Lader's visual analog scales and alternate versions of the Buschke Selective Reminding Test were administered in a repeated measures design at baseline, 1, 2.5, and 5 hours postdrug administration.

RESULTS

A 2.0-mg oral dose of trihexyphenidyl resulted in increased subjective ratings of mental slowness in carriers of the APOE epsilon4 allele only. Drug effects as determined by difference scores between 2.0 mg trihexyphenidyl and placebo on ratings of mental slowness significantly correlated with total and delayed recall on the Buschke Selective Reminding Test in carriers of the APOE epsilon4 allele only. However, no significant effects were found with other visual analog scales reflecting subjective sedation and clear-headedness.

CONCLUSION

The epsilon4 allele in healthy elderly was associated with increased subjective mental slowing after trihexyphenidyl anticholinergic challenge.

Détournement d’usage du trihexyphénidyle (Artane®, Parkinane®) : tendances récentes

Recent observations suggest the existence of trihexyphenidyl abuse linked to its hallucinogenic and euphoric effects. In order to determine the importance of this practice and the characteristics of those involved, a study based on data from the Provence-Alpes-Côte-d'Azur and the Corsica health reimbursement system was carried out. Individuals from these regions affiliated to the French health reimbursement system who had a prescription for trihexyphenidyl (Artane, Parkinane) reimbursed between January 1, 2001, and February 15, 2001, were selected. The delivery of prescriptions was monitored over a 9-month period. In total, 3028 subjects were selected. A subgroup comprising 2.1% of subjects with deviant behaviour was identified by factorial analysis and compared with the subgroup without deviant behaviour. The subjects with deviant behaviour were young and mostly male. The dosage of trihexyphenidyl was higher in these subjects (28 mg/day versus 7 mg/day) and a greater proportion used benzodiazepine and high-dose buprenorphine compared with those without deviant behaviour. The number of prescriptions delivered was higher (23.0 versus 7.7) as well the number of different physicians (4.9 versus 1.5) and pharmacies (5.0 versus 1.3) for those subjects with deviant behaviour. This study confirms the abuse and dependence potential associated with trihexyphenidyl use and the need to increase the supervision of this drug.

Muscarinic mechanisms of antipsychotic atypicality

The interactions of the atypical antipsychotic drugs (APD) clozapine, olanzapine, risperidone, quetiapine and ziprasidone with muscarinic receptors were reviewed. Only clozapine and olanzapine have marked affinity for muscarinic receptors in radioligand binding studies; however, the affinity of these compounds is considerably lower than classical muscarinic antagonists. Although functional assays in cell lines transfected with muscarinic receptors suggest that olanzapine and clozapine have weak partial agonist activity at muscarinic receptors, particularly M4 receptors, studies in vitro and in vivo indicate that the compounds function as antagonists. In animal studies and in humans, clozapine has pronounced antimuscarinic effects whereas olanzapine has weak antimuscarinic effects. However, olanzapine significantly occupies central muscarinic receptors in humans. Overall, the role of muscarinic receptors in the antipsychotic effects of clozapine and olanzapine is controversial and complex.

Amnesic effects of the anticholinergic drugs, trihexyphenidyl and biperiden: differences in binding properties to the brain muscarinic receptor

An amnesic effect of anticholinergic drugs was previously described from several behavioral studies. We examined this effect induced by trihexyphenidyl and biperiden, clinically used in the parkinsonism and schizophrenic patients, by using passive avoidance tasks. Both of these drugs (0.1-10 mg/kg, s.c.) showed dose-dependent amnesic effects in the acquisition and retrieval phases. However, the effect induced by trihexyphenidyl was transient, whereas that of biperiden was long-lasting. To clarify the reason for the different duration of the amnesic activity, binding to the muscarinic receptor was examined. In the Scatchard analysis, trihexyphenidyl competed with [(3)H]quinuclidinyl benzilate ([(3)H]QNB) on the muscarinic receptor (showed increased K(d) and unchanged B(max) value), while biperiden decreased [(3)H]QNB binding (B(max) value) significantly. Furthermore, in an exchange assay for receptor inactivation, trihexyphenidyl binding to muscarinic receptors was exchanged by [(3)H]QNB completely, but biperiden decreased the exchangeable binding of [(3)H]QNB in a dose dependent manner (0.1-100 nM). These results suggested that the binding of trihexyphenidyl and biperiden to muscarinic receptor might be completely reversible and partially irreversible, respectively, whereas the K(i) values of these two drugs were similar. In conclusion, this difference in binding property may explain the difference in the time-course of the amnesic effect induced by trihexyphenidyl and biperiden.

Differential effects of anticholinergic drugs on paired discrimination performance

Working and reference memory processes were simultaneously evaluated during the performance of a paired discrimination (PD) task in which visual and spatial discrimination trials were combined within the same session. Atropine (1 and 5 mg/kg), scopolamine (0.02-0.20 mg/kg), benactyzine (1-4 mg/kg), trihexyphenidyl (1-10 mg/kg), and aprophen (5-20 mg/kg) were all found to increase the number of errors performed by overtrained rats during the spatial but not during the visual trials. Although all the anticholinergic drugs tested induced specific working memory impairment at low doses, they differentially affected other, simultaneously recorded, behavioral parameters. Thus, while atropine affected most of the recorded parameters, aprophen induced only a mild effect. Benactyzine was found to have the most specific effect on working memory, with only minimal side effects, a combination that supports its use as the preferred psychopharmacological model of working memory impairment.