Age-related changes in antidepressant pharmacokinetics and potential drug-drug interactions: a comparison of evidence-based literature and package insert information

Psychotropic Drug-Related Weight Gain and Its Treatment

Psychotropic drug-related weight gain (PDWG) is a common occurrence and is highly associated with non-initiation, discontinuation, and dissatisfaction with psychiatric drugs. Moreover, PDWG intersects with the elevated risk for obesity and associated morbidity that has been amply reported in the psychiatric population. Evidence indicates that differential liability for PDWG exists for antipsychotics, antidepressants, and anticonvulsants. During the past two decades, agents within these classes have become available with significantly lower or no liability for PDWG and as such should be prioritized. Although lithium is associated with weight gain, the overall extent of weight gain is significantly lower than previously estimated. The benefit of lifestyle and behavioral modification for obesity and/or PDWG in psychiatric populations is established, with effectiveness similar to that in the general population. Metformin is the most studied pharmacological treatment in the prevention and treatment of PDWG, and promising data are emerging for glucagon-like peptide-1 (GLP-1) receptor agonists (e.g., liraglutide, exenatide, semaglutide). Most pharmacologic antidotes for PDWG are supported with low-confidence data (e.g., topiramate, histamine-2 receptor antagonists). Future vistas for pharmacologic treatment for PDWG include large, adequately controlled studies with GLP-1 receptor agonists and possibly GLP-1/glucose-dependent insulinotropic polypeptide co-agonists (e.g., tirzepatide) as well as specific dietary modifications.

Identification of an optimal dose of intravenous ketamine for late-life treatment-resistant depression: a Bayesian adaptive randomization trial

Evidence supporting specific therapies for late-life treatment-resistant depression (LL-TRD) is necessary. This study used Bayesian adaptive randomization to determine the optimal dose for the probability of treatment response (≥50% improvement from baseline on the Montgomery-Åsberg Depression Rating Scale) 7 days after a 40 min intravenous (IV) infusion of ketamine 0.1 mg/kg (KET 0.1), 0.25 mg/kg (KET 0.25), or 0.5 mg/kg (KET 0.5), compared to midazolam 0.03 mg/kg (MID) as an active placebo. The goal of this study was to identify the best dose to carry forward into a larger clinical trial. Response durability at day 28, safety and tolerability, and effects on cortical excitation/inhibition (E/I) ratio using resting electroencephalography gamma and alpha power, were also determined. Thirty-three medication-free US military veterans (mean age 62; range: 55-72; 10 female) with LL-TRD were randomized double-blind. The trial was terminated when dose superiority was established. All interventions were safe and well-tolerated. Pre-specified decision rules terminated KET 0.1 (N = 4) and KET 0.25 (N = 5) for inferiority. Posterior probability was 0.89 that day-seven treatment response was superior for KET 0.5 (N = 11; response rate = 70%) compared to MID (N = 13; response rate = 46%). Persistent treatment response at day 28 was superior for KET 0.5 (response rate = 82%) compared to MID (response rate = 37%). KET 0.5 had high posterior probability of increased frontal gamma power (posterior probability = 0.99) and decreased posterior alpha power (0.89) during infusion, suggesting an acute increase in E/I ratio. These results suggest that 0.5 mg/kg is an effective initial IV ketamine dose in LL-TRD, although further studies in individuals older than 75 are required.

Polypharmacy and Mental Health Issues in the Senior Hemodialysis Patient

Hemodialysis (HD) is the most common method of chronic kidney failure (CKF) treatment, with 65% of European patients with CKF receiving HD in 2018. Regular two to three HD sessions weekly severely lower their quality of life, resulting in a higher incidence of depression and anxiety, which is present in one third to one half of these patients. Additionally, the age of patients receiving HD is increasing with better treatment and care, resulting in more cognitive impairment being uncovered. Lastly, patients with other mental health issues can also develop CKF during their life with need for kidney replacement therapy (KRT). All these conditions need to receive adequate care, which often means prescribing psychotropic medications. Importantly, many of these drugs are eliminated through the kidneys, which results in altered pharmacokinetics when patients receive KRT. This narrative review will focus on common issues and medications of CKF patients, their comorbidities, mental health issues, use of psychotropic medications and their altered pharmacokinetics when used in HD, polypharmacy, and drug interactions, as well as deprescribing algorithms developed for these patients.

Prevalence of potentially harmful multidrug interactions on medication lists of elderly ambulatory patients

Background

It has been hypothesized that polypharmacy may increase the frequency of multidrug interactions (MDIs) where one drug interacts with two or more other drugs, amplifying the risk of associated adverse drug events (ADEs). The main objective of this study was to determine the prevalence of MDIs in medication lists of elderly ambulatory patients and to identify the medications most commonly involved in MDIs that amplify the risk of ADEs.

Methods

Medication lists stored in the electronic health record (EHR) of 6,545 outpatients ≥60 years old were extracted from the enterprise data warehouse. Network analysis identified patients with three or more interacting medications from their medication lists. Potentially harmful interactions were identified from the enterprise drug-drug interaction alerting system. MDIs were considered to amplify the risk if interactions could increase the probability of ADEs.

Results

MDIs were identified in 1.3 % of the medication lists, the majority of which involved three interacting drugs (75.6 %) while the remainder involved four (15.6 %) or five or more (8.9 %) interacting drugs. The average number of medications on the lists was 3.1 ± 2.3 in patients with no drug interactions and 8.6 ± 3.4 in patients with MDIs. The prevalence of MDIs on medication lists was greater than 10 % in patients prescribed bupropion, tramadol, trazodone, cyclobenzaprine, fluoxetine, ondansetron, or quetiapine and greater than 20 % in patients prescribed amiodarone or methotrexate. All MDIs were potentially risk-amplifying due to pharmacodynamic interactions, where three or more medications were associated with the same ADE, or pharmacokinetic, where two or more drugs reduced the metabolism of a third drug. The most common drugs involved in MDIs were psychotropic, comprising 35.1 % of all drugs involved. The most common serious potential ADEs associated with the interactions were serotonin syndrome, seizures, prolonged QT interval and bleeding.

Conclusions

An identifiable number of medications, the majority of which are psychotropic, may be involved in MDIs in elderly ambulatory patients which may amplify the risk of serious ADEs. To mitigate the risk, providers will need to pay special attention to the overlapping drug-drug interactions which result in MDIs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12877-021-02594-z.

Molecular imaging of the serotonin transporter availability and occupancy by antidepressant treatment in late-life depression

Patients with late-life depression (LLD) have a more variable response to pharmacotherapy relative to patients with mid-life depression. Degeneration of the serotonergic system and lower occupancy of the initial target for antidepressant medications, the serotonin transporter (5-HTT), may contribute to variability in treatment response. The focus of this study was to test the hypotheses that lower cortical and limbic serotonin transporter (5-HTT) availability in LLD patients relative to controls and less 5-HTT occupancy by antidepressant medications would be associated with less improvement in mood and cognition with treatment in LLD patients. Twenty LLD patients meeting DSM-IV criteria for a current major depressive episode and 20 non-depressed controls underwent clinical and neuropsychological assessments, magnetic resonance imaging to measure gray matter volumes and high-resolution positron emission tomography (PET) scanning to measure 5-HTT before and after 10-12 weeks of treatment with Citalopram or Sertraline (patients only). Prior to treatment, 5-HTT was lower in LLD patients relative to controls in mainly temporal cortical and limbic (amygdala and hippocampus) regions. Gray matter volumes were not significantly different between groups. 5-HTT occupancy was detected throughout cortical, striatal, thalamic and limbic regions. The magnitude of regional 5-HTT occupancy by antidepressants was 70% or greater across cortical and sub-cortical regions, consistent with the magnitude of 5-HTT occupancy observed in mid-life depressed patients. Greater regional 5-HTT occupancy correlated with greater improvement in depressive symptoms and visual-spatial memory performance. These data support the hypothesis that serotonin degeneration and variability in 5-HTT occupancy may contribute to heterogeneity in treatment response in LLD patients.

Depression From a Precision Mental Health Perspective: Utilizing Personalized Conceptualizations to Guide Personalized Treatments

Modern research has proven that the "typical patient" requiring standardized treatments does not exist, reflecting the need for more personalized approaches for managing individual clinical profiles rather than broad diagnoses. In this regard, precision psychiatry has emerged focusing on enhancing prevention, diagnosis, and treatment of psychiatric disorders through identifying clinical subgroups, suggesting personalized evidence-based interventions, assessing the effectiveness of different interventions, and identifying risk and protective factors for remission, relapse, and vulnerability. Literature shows that recent advances in the field of precision psychiatry are rapidly becoming more data-driven reflecting both the significance and the continuous need for translational research in mental health. Different etiologies underlying depression have been theorized and some factors have been identified including neural circuitry, biotypes, biopsychosocial markers, genetics, and metabolomics which have shown to explain individual differences in pathology and response to treatment. Although the precision approach may prove to enhance diagnosis and treatment decisions, major challenges are hindering its clinical translation. These include the clinical diversity of psychiatric disorders, the technical complexity and costs of multiomics data, and the need for specialized training in precision health for healthcare staff, besides ethical concerns such as protecting the privacy and security of patients' data and maintaining health equity. The aim of this review is to provide an overview of recent findings in the conceptualization and treatment of depression from a precision mental health perspective and to discuss potential challenges and future directions in the application of precision psychiatry for the treatment of depression.

Optimal doses of antidepressants in dependence on age: Combined covariate actions in Bayesian network meta-analysis

Background: The meta-analysis by Furukawa et al. (The Lancet Psychiatry 2019, 6(7)) reported optimal doses for antidepressants in adult major depressive disorder (MDD). The present reanalysis aimed to adjust optimal doses in dependence on age. Methods: Analysis was based on the same dataset by Cipriani et al. (The Lancet 2018, 391(10128)) comparing 21 antidepressants in MDD. Random-effects Bayesian network meta-analysis was implemented to estimate the combined covariate action using restricted cubic splines (RCS). Balanced treatment recommendations were derived for the outcomes efficacy (response), acceptability (dropouts for any reason), and tolerability (dropouts due to adverse events). Findings: The combined covariate action of dose and age suggested agomelatine and escitalopram as the best-balanced antidepressants in terms of efficacy and tolerability that may be escalated until 40 and 60 mg/day fluoxetine equivalents (mg/day _FE ), respectively, for ages 30-65 years. Desvenlafaxine, duloxetine, fluoxetine, milnacipran, and vortioxetine may be escalated until 20-40 mg/day _FE , whereas bupropion, citalopram, mirtazapine, paroxetine, and venlafaxine may not be given in doses  > 20 mg/day _FE . Amitriptyline, clomipramine, fluvoxamine, levomilnacipran, reboxetine, sertraline, and trazodone revealed no relevant balanced benefits and may therefore not be recommended for antidepressant treatment. None of the antidepressants was observed to provide balanced benefits in patients >70 years because of adverse events exceeding efficacy. Interpretation: Findings suggest that the combined covariate action of dose and age provides a better basis for judging antidepressant clinical benefits than considering dose or age separately, and may thus inform decision makers to accurately guide antidepressant dosing recommendations in MDD. Funding: No funding.

Geriatric Polypharmacy: Pharmacist as Key Facilitator in Assessing for Falls Risk: 2019 Update

This article highlights the significant health impact of falls among older adults. An emphasis is placed on the vital role of the pharmacist, regardless of practice setting, in assessing and reducing falls risk for this growing population. In addition, the importance of a stepwise comprehensive approach to falls assessment by pharmacists in collaboration with other clinicians is elucidated.

Pharmacogenetic guidelines and decision support tools for depression treatment: application to late-life

Late-life depression (LLD) is a major depressive disorder that affects someone after the age of 60 years. LLD is frequently associated with inadequate response and remission from antidepressants, in addition to polypharmacy. Pharmacogenetics offers a promising approach to improve clinical outcomes in LLD via new discoveries determining the genetic basis of response rates and side effects, as well as the development of tailored pharmacogenetic-based decision support tools. This invited review evaluates the LLD pharmacogenetic evidence base and the extent to which this was incorporated into existing commercial decision support tools and clinical pharmacogenetic guidelines.

Serotonergic and cholinergic modulation of functional brain connectivity: A comparison between young and older adults

Aging is accompanied by changes in neurotransmission. To advance our understanding of how aging modifies specific neural circuitries, we examined serotonergic and cholinergic stimulation with resting state functional magnetic resonance imaging (RS-fMRI) in young and older adults. The instant response to the selective serotonin reuptake inhibitor citalopram (30 mg) and the acetylcholinesterase inhibitor galantamine (8 mg) was measured in 12 young and 17 older volunteers during a randomized, double blind, placebo-controlled, crossover study. A powerful dataset consisting of 522 RS-fMRI scans was obtained by acquiring multiple scans per subject before and after drug administration. Group × treatment interaction effects on voxelwise connectivity with ten functional networks were investigated (p < .05, FWE-corrected) using a non-parametric multivariate analysis technique with cerebrospinal fluid, white matter, heart rate and baseline measurements as covariates. Both groups showed a decrease in sensorimotor network connectivity after citalopram administration. The comparable findings after citalopram intake are possibly due to relatively similar serotonergic systems in the young and older subjects. Galantamine altered connectivity between the occipital visual network and regions that are implicated in learning and memory in the young subjects. The lack of a cholinergic response in the elderly might relate to the well-known association between cognitive and cholinergic deterioration at older age.

Pharmacokinetics, Safety, and Tolerability of Vortioxetine Following Single- and Multiple-Dose Administration in Healthy Japanese Adults

Three phase 1 randomized single-center studies assessed the pharmacokinetics, safety, and tolerability of vortioxetine after single- and multiple-dose administration in healthy Japanese adults. Study 1 assessed the pharmacokinetics of vortioxetine after administration of single rising doses to men and multiple doses to men and women; study 2 evaluated vortioxetine pharmacokinetics in elderly adults; and study 3 assessed food effects on vortioxetine pharmacokinetics in healthy men. The primary end points included pharmacokinetic parameters of vortioxetine and incidence of adverse events (AEs). Across all studies, 130 participants were randomized and 128 participants completed the studies. Vortioxetine was absorbed and eliminated from plasma slowly, and exposure to vortioxetine increased in an almost dose-proportional manner. No clinically significant differences in the pharmacokinetics of vortioxetine or its metabolites were observed between the sexes in young and elderly adults. Study 3 demonstrated that vortioxetine and its metabolites had similar pharmacokinetics when administered in the fasted and fed states. Importantly, vortioxetine was safe and tolerated, with incidence of AEs comparable to that of placebo. No deaths or serious AEs leading to trial discontinuation were observed. Overall, vortioxetine pharmacokinetics, safety, and tolerability in Japanese adults were comparable to reports in non-Japanese populations.

Geriatric Polypharmacy: Pharmacist as Key Facilitator in Assessing for Falls Risk

This article highlights the significant health impact of falls among older adults. An emphasis is placed on the vital role of the pharmacist, regardless of practice setting, in assessing and reducing falls risk for this growing population. In addition, the importance of a stepwise comprehensive approach to falls assessment by pharmacists in collaboration with other clinicians is elucidated.

Raising the Minimum Effective Dose of Serotonin Reuptake Inhibitor Antidepressants: Adverse Drug Events

This review focuses on the dose-response of serotonin reuptake inhibitor (SRI) antidepressants for efficacy and for adverse drug events (ADEs). Dose-response is identified by placebo-controlled, double-blind, fixed-dose clinical trials comparing various doses for efficacy and for ADEs. Reports from the great majority of clinical trials have consistently found that the minimum SRI effective dose is usually optimal for efficacy in the treatment of depression disorders, even though most American medical practitioners raise the dose when early antidepressant treatment results are negative or partial. To better understand this issue, the medical literature was comprehensively reviewed to ascertain the degree to which SRI medications resulted in a flat dose response for efficacy and then to identify specific ADEs that are dose-dependent. Strong evidence from fixed-dose trial data for the efficacy of nonascendant, minimum effective doses of SRIs was found for the treatment of both major depression and anxiety disorders. Particularly important was the finding that most SRI ADEs have an ascending dose-response curve. These ADEs include sexual dysfunction, hypertension, cardiac conduction risks, hyperglycemia, decreased bone density, sweating, withdrawal symptoms, and agitation. Thus, routinely raising the SRI dose above the minimum effective dose for efficacy can be counter-productive.

Consensus recommendations for systematic evaluation of drug-drug interaction evidence for clinical decision support

BACKGROUND

Healthcare organizations, compendia, and drug knowledgebase vendors use varying methods to evaluate and synthesize evidence on drug-drug interactions (DDIs). This situation has a negative effect on electronic prescribing and medication information systems that warn clinicians of potentially harmful medication combinations.

OBJECTIVE

The aim of this study was to provide recommendations for systematic evaluation of evidence for DDIs from the scientific literature, drug product labeling, and regulatory documents.

METHODS

A conference series was conducted to develop a structured process to improve the quality of DDI alerting systems. Three expert workgroups were assembled to address the goals of the conference. The Evidence Workgroup consisted of 18 individuals with expertise in pharmacology, drug information, biomedical informatics, and clinical decision support. Workgroup members met via webinar 12 times from January 2013 to February 2014. Two in-person meetings were conducted in May and September 2013 to reach consensus on recommendations.

RESULTS

We developed expert consensus answers to the following three key questions. (i) What is the best approach to evaluate DDI evidence? (ii) What evidence is required for a DDI to be applicable to an entire class of drugs? (iii) How should a structured evaluation process be vetted and validated?

CONCLUSION

Evidence-based decision support for DDIs requires consistent application of transparent and systematic methods to evaluate the evidence. Drug compendia and clinical decision support systems in which these recommendations are implemented should be able to provide higher-quality information about DDIs.

Evaluation of Potential Drug-Drug Interactions with Antidepressants in Two Tertiary Care Hospitals

BACKGROUND

Limited resources of healthcare system and high use of antidepressants have raised some serious concerns regarding proper surveillance system of prescribed medicines. Not much literature is available from Pakistan regarding the potential drug-drug interactions (pDDIs) associated with antidepressants.

OBJECTIVE

The objective of this study was to assess the frequency of pDDIs associated with antidepressants, their severity, significance and their association with patient characteristics.

MATERIALS AND METHODS

A prospective, observational study was conducted in two major hospitals of Karachi for the period of three months. Patient profiles, medication charts, and physician notes were thoroughly reviewed to gather all the relevant information. Inclusion and exclusion criteria were set prior to data collection. The collected data was then analysed using Micromedex Drug-REAX System. Descriptive and binomial logistic regression analysis was used to express results.

RESULTS

Of 245 prescriptions reviewed, 141 prescriptions had at least one pDDI (57.5%). A total of 181 pDDIs were identified in prescription containing antidepressant. The ratio of pDDI per prescriptions was 0.78. 42.5% interactions were moderate in severity, 30% of interactions were rapid in onset, and 43% were considered as significant interactions. Polypharmacy (OR=3.41, p< 0.001) and presence of chronic problems (OR=2.14, p=0.002) were significantly associated with the occurrence of pDDIs. Citalopram and diclofenac (11.6%) was commonly prescribed interacting pair in this study.

CONCLUSION

The findings of this study recorded high frequency of antidepressants associated pDDIs. Our results confirm the significant association of polypharmacy with the occurrence of pDDIs with antidepressants. Future studies are warranted to establish these results by including hospitals in different parts of the country.

Risk-benefit analysis of antidepressant drug treatment in the elderly

Depression in the elderly is a significant health issue that has the potential to seriously affect physical and emotional well-being. Therefore, the treatment of geriatric depression is necessary. Antidepressant treatment in older depressed patients is efficacious, but differences in the effectiveness of different classes of antidepressants have not been demonstrated. However, differences in tolerability profile are most recognizable in the elderly. With ageing, a series of changes occur in the elderly that modify both the pharmacokinetics and pharmacodynamics of antidepressants and may influence the efficacy, tolerability and safety of treatment in the elderly. Comorbidities require the use of other drugs, which increases the possibility of drug-drug interactions. Given these aspects, individualized therapy for each elderly patient is needed to achieve acceptable risk-benefit ratio. Effective treatment of depression in the elderly, which may require combined pharmacological with psychosocial treatment, can decrease both morbidity and mortality; it also may lead to reduced demands on family members and on health-care and social services.

Canadian clinical practice guidelines for the management of anxiety, posttraumatic stress and obsessive-compulsive disorders

BACKGROUND

Anxiety and related disorders are among the most common mental disorders, with lifetime prevalence reportedly as high as 31%. Unfortunately, anxiety disorders are under-diagnosed and under-treated.

METHODS

These guidelines were developed by Canadian experts in anxiety and related disorders through a consensus process. Data on the epidemiology, diagnosis, and treatment (psychological and pharmacological) were obtained through MEDLINE, PsycINFO, and manual searches (1980-2012). Treatment strategies were rated on strength of evidence, and a clinical recommendation for each intervention was made, based on global impression of efficacy, effectiveness, and side effects, using a modified version of the periodic health examination guidelines.

RESULTS

These guidelines are presented in 10 sections, including an introduction, principles of diagnosis and management, six sections (Sections 3 through 8) on the specific anxiety-related disorders (panic disorder, agoraphobia, specific phobia, social anxiety disorder, generalized anxiety disorder, obsessive-compulsive disorder, and posttraumatic stress disorder), and two additional sections on special populations (children/adolescents, pregnant/lactating women, and the elderly) and clinical issues in patients with comorbid conditions.

CONCLUSIONS

Anxiety and related disorders are very common in clinical practice, and frequently comorbid with other psychiatric and medical conditions. Optimal management requires a good understanding of the efficacy and side effect profiles of pharmacological and psychological treatments.

Understanding and preventing drug-drug and drug-gene interactions

Concomitant administration of multiple drugs can lead to unanticipated drug interactions and resultant adverse drug events with their associated costs. A more thorough understanding of the different cytochrome P450 isoenzymes and drug transporters has led to new methods to try to predict and prevent clinically relevant drug interactions. There is also an increased recognition of the need to identify the impact of pharmacogenetic polymorphisms on drug interactions. More stringent regulatory requirements have evolved for industry to classify cytochrome inhibitors and inducers, test the effect of drug interactions in the presence of polymorphic enzymes, and evaluate multiple potentially interacting drugs simultaneously. In clinical practice, drug alert software programs have been developed. This review discusses drug interaction mechanisms and strategies for screening and minimizing exposure to drug interactions. We also provide future perspectives for reducing the risk of clinically significant drug interactions.

Dynamic enhancement of drug product labels to support drug safety, efficacy, and effectiveness

Out-of-date or incomplete drug product labeling information may increase the risk of otherwise preventable adverse drug events. In recognition of these concerns, the United States Federal Drug Administration (FDA) requires drug product labels to include specific information. Unfortunately, several studies have found that drug product labeling fails to keep current with the scientific literature. We present a novel approach to addressing this issue. The primary goal of this novel approach is to better meet the information needs of persons who consult the drug product label for information on a drug's efficacy, effectiveness, and safety. Using FDA product label regulations as a guide, the approach links drug claims present in drug information sources available on the Semantic Web with specific product label sections. Here we report on pilot work that establishes the baseline performance characteristics of a proof-of-concept system implementing the novel approach. Claims from three drug information sources were linked to the Clinical Studies, Drug Interactions, and Clinical Pharmacology sections of the labels for drug products that contain one of 29 psychotropic drugs. The resulting Linked Data set maps 409 efficacy/effectiveness study results, 784 drug-drug interactions, and 112 metabolic pathway assertions derived from three clinically-oriented drug information sources (ClinicalTrials.gov, the National Drug File - Reference Terminology, and the Drug Interaction Knowledge Base) to the sections of 1,102 product labels. Proof-of-concept web pages were created for all 1,102 drug product labels that demonstrate one possible approach to presenting information that dynamically enhances drug product labeling. We found that approximately one in five efficacy/effectiveness claims were relevant to the Clinical Studies section of a psychotropic drug product, with most relevant claims providing new information. We also identified several cases where all of the drug-drug interaction claims linked to the Drug Interactions section for a drug were potentially novel. The baseline performance characteristics of the proof-of-concept will enable further technical and user-centered research on robust methods for scaling the approach to the many thousands of product labels currently on the market.

Inhibitory metabolic drug interactions with newer psychotropic drugs: inclusion in package inserts and influences of concurrence in drug interaction screening software

BACKGROUND

Food and Drug Administration (FDA) regulations mandate that package inserts (PIs) include observed or predicted clinically significant drug-drug interactions (DDIs), as well as the results of pharmacokinetic studies that establish the absence of effect.

OBJECTIVE

To quantify how frequently observed metabolic inhibition DDIs affecting US-marketed psychotropics are present in FDA-approved PIs and what influence the source of DDI information has on agreement between 3 DDI screening programs.

METHODS

The scientific literature and PIs were reviewed to determine all drug pairs for which there was rigorous evidence of a metabolic inhibition interaction or noninteraction. The DDIs were tabulated noting the source of evidence and the strength of agreement over chance. Descriptive statistics were used to examine the influence of source of DDI information on agreement among 3 DDI screening tools. Logistic regression was used to assess the influence of drug class, indication, generic status, regulatory approval date, and magnitude of effect on agreement between the literature and PI as well as agreement among the DDI screening tools.

RESULTS

Thirty percent (13/44) of the metabolic inhibition DDIs affecting newer psychotropics were not mentioned in PIs. Drug class, indication, regulatory approval date, generic status, or magnitude of effect did not appear to be associated with more complete DDI information in PIs. DDIs found exclusively in PIs were 3.25 times more likely to be agreed upon by all 3 DDI screening tools than were those found exclusively in the literature. Generic status was inversely associated with agreement among the DDI screening tools (odds ratio 0.11; 95% CI 0.01 to 0.89).

CONCLUSIONS

The presence in PIs of DDI information for newer psychotropics appears to have a strong influence on agreement among DDI screening tools. Users of DDI screening software should consult more than 1 source when considering interactions involving generic psychotropics.