Assessing and predicting drug-induced anticholinergic risks: an integrated computational approach

Comparative analysis of anticholinergic burden scales to explain iatrogenic cognitive impairment and self-reported side effects in the euthymic phase of bipolar disorders: Results from the FACE-BD cohort

Bipolar disorders (BD) are characterized by cognitive impairment during the euthymic phase, to which treatments can contribute. The anticholinergic properties of medications, i.e., the ability of a treatment to inhibit cholinergic receptors, are associated with cognitive impairment in elderly patients and people with schizophrenia but this association has not been well characterized in individuals with remitted BD. Moreover, the validity of only one anticholinergic burden scale designed to assess the anticholinergic load of medications has been tested in BD. In a literature review, we identified 31 existing scales. We first measured the associations between 27 out of the 31 scales and objective cognitive impairment in bivariable regressions. We then adjusted the bivariable models with covariates: the scales significantly associated with cognitive impairment in bivariable and multiple logistic regressions were defined as having good concurrent validity to assess cognitive impairment. In a sample of 2,031 individuals with euthymic BD evaluated with a neuropsychological battery, two scales had good concurrent validity to assess cognitive impairment, whereas chlorpromazine equivalents, lorazepam equivalents, the number of antipsychotics, or the number of treatments had not. Finally, similar analyses with subjective anticholinergic side-effects as outcome variables reported 14 scales with good concurrent validity to assess self-reported peripheral anticholinergic side-effects and 13 to assess self-reported central anticholinergic side-effects. Thus, we identified valid scales to monitor the anticholinergic burden in BD, which may be useful in estimating iatrogenic cognitive impairment in studies investigating cognition in BD.

The Prognostic Utility of Anticholinergic Burden Scales: An Integrative Review and Gap Analysis

BACKGROUND

Anticholinergic drugs are commonly prescribed, especially to older adults. Anticholinergic burden scales (ABS) have been used to evaluate the cumulative effects of multiple anticholinergics. However, studies have shown inconsistent results regarding the association between anticholinergic burden assessed with ABS and adverse clinical outcomes such as cognitive impairment, functional decline, and frailty. This review aims to identify gaps in research on the development, validation, and evaluation of ABS, and provide recommendations for future studies.

METHOD

A comprehensive search of five databases (MEDLINE, Embase, PsychInfo, CINAHL, CENTRAL) was conducted for relevant studies published from inception until 25 May 2023. Two reviewers screened for eligibility and assessed the quality of studies using different tools based on the study design and stage of the review framework. Research evidence was evaluated, and gaps were identified and grouped into evidence, knowledge, and methodological gaps, using evidence tables to summarize data.

RESULTS

Several evidence, knowledge, and methodological gaps in existing development, validation, and evaluation studies of ABS were identified. There is no universally accepted scale, and there is a need to define a clinically relevant threshold for measuring total anticholinergic burden. The current evidence has limitations, underrepresenting low- and middle-income countries, younger individuals, and populations with cognitive disabilities. The impact of anticholinergic burden on frailty is also understudied. Existing evaluation studies provide limited evidence on the benefit of reducing anticholinergic burden on clinical outcomes or the safety of anticholinergic deprescribing. There is also uncertainty regarding optimal reduction, clinically significant anticholinergic burden thresholds, and cost effectiveness.

CONCLUSIONS

Future research recommendations to bridge knowledge gaps include developing a risk assessment framework, refining ABS scales, establishing a standardized consensus scale, and creating a longitudinal measure of cumulative anticholinergic risk. Strategies to minimize bias, consider frailty, and promote multidisciplinary and multinational collaborations are also necessary to improve patient outcomes.

Development of the Swedish anticholinergic burden scale (Swe-ABS)

BACKGROUND

Drugs with anticholinergic properties are associated with cognitive adverse effects, especially in patients vulnerable to central muscarinic antagonism. A variety of drugs show weak, moderate or strong anticholinergic effects. Therefore, the cumulative anticholinergic burden should be considered in patients with cognitive impairment. This study aimed to develop a Swedish Anticholinergic Burden Scale (Swe-ABS) to be used in health care and research.

METHODS

A systematic literature review was conducted in PubMed and Ovid Embase to identify previously published tools quantifying anticholinergic drug burden (i.e., exposure). Drugs and grading scores (0-3, no to high anticholinergic activity) were extracted from identified lists. Enteral and parenteral drugs authorized in Sweden were included. Drugs with conflicting scores in the existing lists were assessed by an expert group. Two drugs that were not previously assessed were also added to the evaluation process.

RESULTS

The systematic literature search identified the following nine anticholinergic burden scales: Anticholinergic Activity Scale, Anticholinergic Burden Classification, updated Anticholinergic Cognitive Burden scale, Anticholinergic Drug Scale, Anticholinergic Load Scale, Anticholinergic Risk Scale, updated Clinician-rated Anticholinergic Scale, German Anticholinergic Burden Scale and Korean Anticholinergic Burden Scale. A list of drugs with significant anticholinergic effects provided by The Swedish National Board of Health and Welfare was included in the process. The suggested Swe-ABS consists of 104 drugs scored as having weak, moderate or strong anticholinergic effects. Two hundred and fifty-six drugs were listed as having no anticholinergic effects based on evaluation in previous scales. In total, 62 drugs were assessed by the expert group.

CONCLUSIONS

Swe-ABS is a simplified method to quantify the anticholinergic burden and is easy to use in clinical practice. Publication of this scale might make clinicians more aware of drugs with anticholinergic properties and patients' total anticholinergic burden. Further research is needed to validate the Swe-ABS and evaluate anticholinergic exposure versus clinically significant outcomes.

A Universal Pharmacological-Based List of Drugs with Anticholinergic Activity

Anticholinergic burden tools have relevant pharmacological gaps that may explain their limited predictive ability for clinical outcomes. The aim of this study was to provide a universal pharmacological-based list of drugs with their documented affinity for muscarinic receptors. A comprehensive literature review was performed to identify the anticholinergic burden tools. Drugs included in these instruments were searched in four pharmacological databases, and the investigation was supplemented with PubMed. The evidence regarding the potential antagonism of the five muscarinic receptors of each drug was assessed. The proportion of drugs included in the tools with an affinity for muscarinic receptors was evaluated. A universal list of drugs with anticholinergic activity was developed based on their documented affinity for the different subtypes of muscarinic receptors and their ability to cross the blood-brain barrier. A total of 23 tools were identified, including 304 different drugs. Only 48.68%, 47.70%, 48.03%, 43.75%, and 42.76% of the drugs had an affinity to the M1, M2, M3, M4, and M5 receptor, respectively, reported in any pharmacological database. The proportion of drugs with confirmed antagonism varied among the tools (36.8% to 100%). A universal pharmacological-based list of 133 drugs is presented. It should be further validated in different clinical settings.

Evaluation of the association of anticholinergic burden and delirium in older hospitalised patients - A cohort study comparing 19 anticholinergic burden scales

AIMS

A recent review identified 19 anticholinergic burden scales (ABSs) but no study has yet compared the impact of all 19 ABSs on delirium. We evaluated whether a high anticholinergic burden as classified by each ABS is associated with incident delirium.

METHOD

We performed a retrospective cohort study in a Swiss tertiary teaching hospital using data from 2015-2018. Included were patients aged ≥65, hospitalised ≥48 hours with no stay >24 hours in intensive care. Delirium was defined twofold: (i) ICD-10 or CAM and (ii) ICD-10 or CAM or DOSS. Patients' cumulative anticholinergic burden score, calculated within 24 hours after admission, was classified using a binary (<3: low, ≥3: high burden) and a categorical approach (0: no, 0.5-3: low, ≥3: high burden). Association was analysed using multivariable logistic regression.

RESULTS

Over 25 000 patients (mean age 77.9 ± 7.6 years) were included. Of these, (i) 864 (3.3%) and (ii) 2770 (11.0%) developed delirium. Depending on the evaluated ABS, 4-63% of the patients were exposed to at least one anticholinergic drug. Out of 19 ABSs, (i) 14 and (ii) 16 showed a significant association with the outcomes. A patient with a high anticholinergic burden score had odds ratios (ORs) of 1.21 (95% confidence interval [CI]: 1.03-1.42) to 2.63 (95% CI: 2.28-3.03) for incident delirium compared to those with low or no burden.

CONCLUSION

A high anticholinergic burden within 24 hours after admission was significantly associated with incident delirium. Although prospective studies need to confirm these results, discontinuing or substituting drugs with a score of ≥3 at admission might be a targeted intervention to reduce incident delirium.

Clinical Utility of Medication-Based Risk Scores to Reduce Polypharmacy and Potentially Avoidable Healthcare Utilization

The management of multiple chronic health conditions often requires patients to be exposed to polypharmacy to improve their health and enhance their quality of life. However, exposure to polypharmacy has been associated with an increased risk for adverse effects, drug-drug interactions, inappropriate prescribing, medication nonadherence, increased healthcare utilization such as emergency department visits and hospitalizations, and costs. Medication-based risk scores have been utilized to identify patients who may benefit from deprescribing interventions and reduce rates of inappropriate prescribing. These risk scores may also be utilized to prompt targeted discussions between patients and providers regarding medications or medication classes contributing to an individual’s risk for harm, eventually leading to the deprescribing of the offending medication(s). This opinion will describe existing medication-based risk scores in the literature, their utility in identifying patients at risk for specific adverse events, and how they may be incorporated in healthcare settings to reduce rates of potentially inappropriate polypharmacy and avoidable healthcare utilization and costs.

High anticholinergic burden at admission associated with in-hospital mortality in older patients: A comparison of 19 different anticholinergic burden scales

Although no gold standard exists to assess a patient's anticholinergic burden, a review identified 19 anticholinergic burden scales (ABSs). No study has yet evaluated whether a high anticholinergic burden measured with all 19 ABSs is associated with in‐hospital mortality and length of stay (LOS). We conducted a cohort study at a Swiss tertiary teaching hospital using patients' electronic health record data from 2015–2018. Included were patients aged ≥65 years, hospitalised ≥48 h without stays and >24 h in intensive care. Patients' cumulative anticholinergic burden score was classified using a binary (<3: low, ≥3: high) and categorical approach (0: no, 0.5–3: low, ≥3: high). In‐hospital mortality and LOS were analysed using multivariable logistic and linear regression, respectively. We included 27,092 patients (mean age 78.0 ± 7.5 years, median LOS 6 days). Of them, 913 died. Depending on the evaluated ABS, 1370 to 17,035 patients were exposed to anticholinergics. Patients with a high burden measured by all 19 ABSs were associated with a 1.32‐ to 3.03‐fold increase in in‐hospital mortality compared with those with no/low burden. We obtained similar results for LOS. To conclude, discontinuing drugs with anticholinergic properties (score ≥3) at admission might be a targeted intervention to decrease in‐hospital mortality and LOS.

Quantifying Anticholinergic Burden and Sedative Load in Older Adults with Polypharmacy: A Systematic Review of Risk Scales and Models

BACKGROUND

Patients taking medication with high anticholinergic and sedative properties are at increased risk of experiencing poor cognitive and physical outcomes. Therefore, precise quantification of the cumulative burden of their drug regimen is advisable. There is no agreement regarding which scale to use to simultaneously quantify the burden associated with medications.

OBJECTIVES

The objective of this review was to assess the strengths and limitations of available tools to quantify medication-related anticholinergic burden and sedative load in older adults. We discuss specific limitations and agreements between currently available scales and models and propose a comprehensive table combining drugs categorized as high, moderate, low, or no anticholinergic or sedative activity as excerpted from the selected studies.

METHODS

A targeted search was carried out using the National Library of Medicine through PubMed using medical subject heading terms and text words around the following search terms: (anticholinergic OR sedative) AND (load OR burden OR scale) for studies published between 1 January 1945 and 5 June 2021. In addition, the following databases were searched using the same terms: MEDLINE-EBSCO, APA PsycInfo, CINAHL Plus, Cochrane Library, Scopus, OAIster, OVID-MEDLINE, Web of Science, and Google Scholar. Screening by titles was followed by an abstract and full-text review. After blind evaluation, agreement between reviewers was reached to establish drug characteristics and categories.

RESULTS

After 3163 articles were identified, 13 were included: 11 assigned risk scores to anticholinergic drugs and two to sedative drugs. Considerable variability between anticholinergic scales was observed; scales included between 27 and 548 drugs. We generated a comprehensive table combining the anticholinergic and sedative activities of drugs evaluated and proposed a categorization of these drugs based on available scientific and clinical evidence. Our table combines information about 642 drugs and categorizes 44, 25, 99, and 474 drugs as high, moderate, low, or no anticholinergic and sedative activity, respectively.

CONCLUSIONS

Variability and inconsistency exists among scales used to categorize drugs with anticholinergic or sedative burden. In this review, we provide a comprehensive table that proposes a new categorization of these drugs. A longitudinal study will be required to validate the new proposed anticholinergic and sedative burden catalog in an evidence-based manner.

Anticholinergic medication: Related dry mouth and effects on the salivary glands

OBJECTIVE

Salivary glands are among the most sensitive target organs of medications with anticholinergic (AC) properties, interrupting the neural stimulation of saliva secretion and reducing saliva flow. Hyposalivation results in dry mouth, leading to dental caries, intraoral infection, orofacial pain, problems with speaking and swallowing, and diminished oral health--related quality of life. Current understanding of the pharmacokinetics of AC medications and their effect on muscarinic receptors in the salivary glands were reviewed to assist clinicians in predicting salivary damage in patients with AC medication-induced dry mouth.

STUDY DESIGN

We summarized the literature related to the mechanisms and properties of AC medications, anticholinergic adverse effects, and their effect on salivary function and management strategies to prevent oral health damage.

RESULTS

Although a large number of studies reported on the frequencies of medication-induced dry mouth, we found very limited data on predicting individual susceptibility to AC medication--caused hyposalivation and no prospective clinical studies addressing this issue.

CONCLUSION

Dry mouth is most frequently caused by medications with AC properties, which interrupt the neural stimulation of saliva secretion. Interdisciplinary care should guide pharmacotherapeutics and dental interventions should aim in preventing AC salivary adverse effects and reducing the oral health burden from AC medication-induced dry mouth.

A narrative review of using prescription drug databases for comorbidity adjustment: A less effective remedy or a prescription for improved model fit?

BACKGROUND

The use of claims data for identifying comorbid conditions in patients for research purposes has been widely explored. Traditional measures of comorbid adjustment included diagnostic data (e.g., ICD-9-CM or ICD-10-CM codes), with the Charlson and Elixhauser methodology being the two most common approaches. Prescription data has also been explored for use in comorbidity adjustment, however early methodologies were disappointing when compared to diagnostic measures.

OBJECTIVE

The objective of this methodological review is to compare results from newer studies using prescription-based data with more traditional diagnostic measures.

METHODS

A review of studies found on PubMed, Medline, Embase or CINAHL published between January 1990 and December 2020 using prescription data for comorbidity adjustment. A total of 50 studies using prescription drug measures for comorbidity adjustment were found.

CONCLUSIONS

Newer prescription-based measures show promise fitting models, as measured by predictive ability, for research, especially when the primary outcomes are utilization or drug expenditure rather than diagnostic measures. More traditional diagnostic-based measures still appear most appropriate if the primary outcome is mortality or inpatient readmissions.

Quality of anticholinergic burden scales and their impact on clinical outcomes: a systematic review

PURPOSE

Older people are at risk of anticholinergic side effects due to changes affecting drug elimination and higher sensitivity to drug's side effects. Anticholinergic burden scales (ABS) were developed to quantify the anticholinergic drug burden (ADB). We aim to identify all published ABS, to compare them systematically and to evaluate their associations with clinical outcomes.

METHODS

We conducted a literature search in MEDLINE and EMBASE to identify all published ABS and a Web of Science citation (WoS) analysis to track validation studies implying clinical outcomes. Quality of the ABS was assessed using an adapted AGREE II tool. For the validation studies, we used the Newcastle-Ottawa Scale and the Cochrane tool Rob2.0. The validation studies were categorized into six evidence levels based on the propositions of the Oxford Center for Evidence-Based Medicine with respect to their quality. At least two researchers independently performed screening and quality assessments.

RESULTS

Out of 1297 records, we identified 19 ABS and 104 validations studies. Despite differences in quality, all ABS were recommended for use. The anticholinergic cognitive burden (ACB) scale and the German anticholinergic burden scale (GABS) achieved the highest percentage in quality. Most ABS are validated, yet validation studies for newer scales are lacking. Only two studies compared eight ABS simultaneously. The four most investigated clinical outcomes delirium, cognition, mortality and falls showed contradicting results.

CONCLUSION

There is need for good quality validation studies comparing multiple scales to define the best scale and to conduct a meta-analysis for the assessment of their clinical impact.

Quality of anticholinergic burden scales and their impact on clinical outcomes: a systematic review

Purpose

Older people are at risk of anticholinergic side effects due to changes affecting drug elimination and higher sensitivity to drug’s side effects. Anticholinergic burden scales (ABS) were developed to quantify the anticholinergic drug burden (ADB). We aim to identify all published ABS, to compare them systematically and to evaluate their associations with clinical outcomes.

Methods

We conducted a literature search in MEDLINE and EMBASE to identify all published ABS and a Web of Science citation (WoS) analysis to track validation studies implying clinical outcomes. Quality of the ABS was assessed using an adapted AGREE II tool. For the validation studies, we used the Newcastle-Ottawa Scale and the Cochrane tool Rob2.0. The validation studies were categorized into six evidence levels based on the propositions of the Oxford Center for Evidence-Based Medicine with respect to their quality. At least two researchers independently performed screening and quality assessments.

Results

Out of 1297 records, we identified 19 ABS and 104 validations studies. Despite differences in quality, all ABS were recommended for use. The anticholinergic cognitive burden (ACB) scale and the German anticholinergic burden scale (GABS) achieved the highest percentage in quality. Most ABS are validated, yet validation studies for newer scales are lacking. Only two studies compared eight ABS simultaneously. The four most investigated clinical outcomes delirium, cognition, mortality and falls showed contradicting results.

Conclusion

There is need for good quality validation studies comparing multiple scales to define the best scale and to conduct a meta-analysis for the assessment of their clinical impact.

Electronic supplementary material

The online version of this article (10.1007/s00228-020-02994-x) contains supplementary material, which is available to authorized users.

Use of a Bioinformatics-Based Toxicity Scoring System to Assess Serotonin Burden and Predict Population-Level Adverse Drug Events from Concomitant Serotonergic Drug Therapy

STUDY OBJECTIVE

Numerous medications interact at serotonin (5-hydroxytryptamine [5-HT]) receptors directly or through off-target interactions, causing mild to severe serotonergic adverse drug events (ADEs), particularly among older adults. Our objective was to develop a novel molecular-based toxicity scoring system to assess serotonergic burden resulting from concurrently administered drugs. Quantitative methods to assess serotonergic burden may provide a useful clinical tool for improving pharmacotherapy.

DESIGN

Retrospective cohort study.

DATA SOURCES

PharMetrics Legacy health claims database (January 2001-December 2013) and ChEMBL bioactivity database.

PATIENTS

A 2-serotonergic drug exposure cohort (78,172 patients) and a 3-serotonergic drug exposure cohort (19,900 patients) were generated, and population-level statistics were collected. Nonexposure cohorts were created for each drug exposure cohort and matched in a 4:1 ratio for age, sex, and length of enrollment.

MEASUREMENTS AND MAIN RESULTS

Eight 5-HT medications were screened against multiple bioactivity databases to identify their off-target interactions at 5-HT receptors and serotonin reuptake transporter protein. A computational serotonin burden score (SBS) was derived from the receptor-specific interaction propensities reported from the comprehensive bioactivity screen. Linear regression was used to characterize associations between SBSs and combined total ADE incidence rate detected by International Classification of Diseases, Ninth Revision, Clinical Modification, diagnosis codes. A significantly greater incidence of 17 potential 5-HT-related ADEs was seen in exposed serotonergic drug cohorts (p<0.05). A positive correlation between SBS and overall ADE incidence rate in the 2-serotonergic drug exposure cohort (R²  = 0.69, p<0.34) and 3-drug cohort (R²  = 0.85, p<0.01) was observed. When both drug cohorts were combined, total drug SBSs strongly correlated with the composite 5-HT adverse event rate (R²  = 0.92, p<0.0001). Despite an increasing burden of illness, these data suggest that drug combinations with higher SBSs are associated with a higher rate of potential serotonergic ADEs.

CONCLUSION

In this test of concept, positive associations between SBSs and serotonin-related ADEs suggest that it may offer a pharmacologic-based foundation for developing risk assessment tools to assist in optimizing pharmacotherapy.

Implications of Off-Target Serotoninergic Drug Activity: An Analysis of Serotonin Syndrome Reports Using a Systematic Bioinformatics Approach

Study Objective

Serotonergic adverse drug events (ADEs) are caused by enhanced intrasynaptic concentrations of 5‐hydroxytryptamine (5‐HT). No systematic process currently exists for evaluating cumulative 5‐HT and off‐target toxicity of serotonergic drugs. The primary study aim was to create a Serotonergic Expanded Bioactivity Matrix (SEBM) by using a molecular bioinformatics, polypharmacologic approach for assessment of the participation of individual 5‐HT drugs in serotonin syndrome (SS) reports.

Data Sources

Publicly available databases including the U.S. Food and Drug Administration (FDA) Adverse Event Reporting System (FAERS), ChEMBL, DrugBank, PubChem, and Kyoto Encyclopedia of Genes and Genomes (KEGG) were queried for computational and pharmacologic data.

Design

An in‐house bioinformatics TargetSearch program ( http://dxulab.org/software) was used to characterize 71 serotonergic drugs interacting at 13 serotonin receptor subtypes and serotonin reuptake transporter protein (SERT). In addition, off‐target interactions at norepinephrine transporter (NET), monoamine oxidase (MAO), and muscarinic receptors were included to define seven polypharmacological drug cohorts. Serotonin syndrome reports for each serotonergic drug were extracted from FAERS by using the Sternbach and Hunter criteria.

Measurements and Main Results

A proportional reporting adverse drug reaction (ADR) ratio (PRR) was calculated from each drug's total ADEs and SS case reports and aggregated by drug bioactivity cohorts. Triple‐receptor interactions had a disproportionately higher number of SS cases using both the Hunter criteria (mean PRR 1.72, 95% CI 1.05–2.39) and Sternbach (mean PRR 1.54, 95% CI 1.29–1.79). 5‐Hydroxytryptamine agonists were associated with a significantly lower proportion of SS cases using the Hunter and Sternbach criteria, respectively (mean PRR 0.49, 95% CI 0.17–0.81 and mean PRR 0.49, 95% CI 0.15–0.83). Drugs with disproportionately higher participation in SS vary considerably between the two diagnostic criteria.

Conclusion

The SEBM model suggests a possible polypharmacological role in SS. Although further research is needed, off‐target receptor activity may help explain differences in severity of toxicity and clinical presentation.

MSBIS: A Multi-Step Biomedical Informatics Screening Approach for Identifying Medications that Mitigate the Risks of Metoclopramide-Induced Tardive Dyskinesia

In 2009 the U.S. Food and Drug Administration (FDA) placed a black box warning on metoclopramide (MCP) due to the increased risks and prevalence of tardive dyskinesia (TD). In this study, we developed a multi-step biomedical informatics screening (MSBIS) approach leveraging publicly available bioactivity and drug safety data to identify concomitant drugs that mitigate the risks of MCP-induced TD. MSBIS includes (1) TargetSearch (http://dxulab.org/software) bioinformatics scoring for drug anticholinergic activity using CHEMBL bioactivity data; (2) unadjusted odds ratio (UOR) scoring for indications of TD-mitigating effects using the FDA Adverse Event Reporting System (FAERS); (3) adjusted odds ratio (AOR) re-scoring by removing the effect of cofounding factors (age, gender, reporting year); (4) logistic regression (LR) coefficient scoring for confirming the best TD-mitigating drug candidates. Drugs with increasing TD protective potential and statistical significance were obtained at each screening step. Fentanyl is identified as the most promising drug against MCP-induced TD (coefficient: −2.68; p-value < 0.01). The discovery is supported by clinical reports that patients fully recovered from MCP-induced TD after fentanyl-induced general anesthesia. Loperamide is identified as a potent mitigating drug against a broader range of drug-induced movement disorders through pharmacokinetic modifications. Using drug-induced TD as an example, we demonstrated that MSBIS is an efficient in silico tool for unknown drug-drug interaction detection, drug repurposing, and combination therapy design.

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An in silico MSBIS approach was developed to identify concomitant drugs that mitigate the side effects of a primary drug.

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Fentanyl and loperamide were identified to protect patients against drug-induced tardive dyskinesia (TD).

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MSBIS can be generalized to provide rational starting points for drug repurposing and combination therapy design.

Many dopamine antagonists cause TD and other severe, irreversible movement disorders. 120 drugs were screened using the MSBIS approach, leading to the discovery of fentanyl and loperamide. When co-administered with dopamine antagonists such as metoclopramide, they may protect patients against drug-induced movement disorders including TD. Their mechanisms of toxicity-mitigating action are remarkably different. The statistical significance of the findings was established using the FDA Adverse Event Reporting System and supported by published clinical reports and pharmacologic data. This study demonstrated the feasibility of the MSBIS approach and its applicability in identifying unknown drug-drug interactions that either mitigate undesirable toxicities or synergize therapeutic effects.