Complexity of medication use in the Veterans Affairs healthcare system: Part II. Antidepressant use among younger and older outpatients

Why Are Patients With COVID-19 at Risk for Drug-Drug Interactions?

The goal of this column is to provide information to health care professionals about drug-drug interactions (DDIs) and why DDIs are important to consider in those at serious risk of illness with Coronavirus Disease 2019 (COVID-19). Important considerations discussed in this column include the frequency and complexity of multiple medication use, particularly important for the older patient who often has multiple comorbid illnesses. The column covers the following issues: (1) Why patients at high risk for serious illness from COVID-19 are also at high risk for DDIs. (2) Application of results of pharmacoepidemiological studies to the population at risk for serious COVID-19 illness. (3) Mechanisms underlying DDIs, frequency and potential complexity of DDIs, and how DDIs can present clinically. (4) Methods for preventing or mitigating DDIs. (5) An introduction to the University of Liverpool drug interaction checker as a tool to reduce the risk of adverse DDIs while treating patients for COVID-19. Commentary is also provided on issues related to specific psychiatric and nonpsychiatric medications a patient may be taking. A subsequent column will focus on DDIs between psychiatric medications and emerging COVID-19 treatments, as a detailed discussion of that topic is beyond the scope of this column.

Acquired Stuttering in Veterans of the Wars in Iraq and Afghanistan: The Role of Traumatic Brain Injury, Post-Traumatic Stress Disorder, and Medications

Introduction

Determine the association between acquired stuttering (AS), traumatic brain injury (TBI), and post-traumatic stress disorder (PTSD) in a cohort of 309,675 U.S. Iraq and Afghanistan veterans. The secondary aim was to determine the association between AS and medication patterns for veterans in the sample.

Materials and Methods

Retrospective study using data from the Veterans Health Administration National Repository for veterans deployed in support of combat operations in Iraq and Afghanistan and who received Veterans Health Administration care in 2010 and 2011. We identified stuttering using ICD-9 codes to establish the association between AS, TBI, and PTSD, controlling for demographic characteristics and other comorbidities. Multivariable logistic regression was used to determine the association between comorbid conditions and potentially problematic medications associated with stuttering.

Results

Two hundred thirty-five veterans (0.08%) were diagnosed with AS in the cohort. There was the greater likelihood of an AS diagnosis for veterans with concomitant TBI and PTSD when compared with veterans without these diagnoses. Over 66% of those with stuttering were prescribed at least one medication that affected speech fluency (antidepressants, anxiolytics, and antiepileptic drugs) compared with 35% of those without AS.

Conclusion

Veterans with a comorbid diagnosis of TBI and PTSD were more likely to be diagnosed with AS AOR: 9.77 (95% CI = 6.93-13.78, p < 0.05) and more likely to have been prescribed medications known to affect speech production OR: 3.68 (95% CI = 2.81-4.82, p < 0.05). Clinicians treating veterans with these complex comorbid conditions should consider the impact of medications on speech fluency.

Interventions to improve the appropriate use of polypharmacy for older people

BACKGROUND

Inappropriate polypharmacy is a particular concern in older people and is associated with negative health outcomes. Choosing the best interventions to improve appropriate polypharmacy is a priority, hence interest in appropriate polypharmacy, where many medicines may be used to achieve better clinical outcomes for patients, is growing. This is the second update of this Cochrane Review.

OBJECTIVES

To determine which interventions, alone or in combination, are effective in improving the appropriate use of polypharmacy and reducing medication-related problems in older people.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, CINAHL and two trials registers up until 7 February 2018, together with handsearching of reference lists to identify additional studies.

SELECTION CRITERIA

We included randomised trials, non-randomised trials, controlled before-after studies, and interrupted time series. Eligible studies described interventions affecting prescribing aimed at improving appropriate polypharmacy in people aged 65 years and older, prescribed polypharmacy (four or more medicines), which used a validated tool to assess prescribing appropriateness. These tools can be classified as either implicit tools (judgement-based/based on expert professional judgement) or explicit tools (criterion-based, comprising lists of drugs to be avoided in older people).

DATA COLLECTION AND ANALYSIS

Two review authors independently reviewed abstracts of eligible studies, extracted data and assessed risk of bias of included studies. We pooled study-specific estimates, and used a random-effects model to yield summary estimates of effect and 95% confidence intervals (CIs). We assessed the overall certainty of evidence for each outcome using the GRADE approach.

MAIN RESULTS

We identified 32 studies, 20 from this update. Included studies consisted of 18 randomised trials, 10 cluster randomised trials (one of which was a stepped-wedge design), two non-randomised trials and two controlled before-after studies. One intervention consisted of computerised decision support (CDS); and 31 were complex, multi-faceted pharmaceutical-care based approaches (i.e. the responsible provision of medicines to improve patient's outcomes), one of which incorporated a CDS component as part of their multi-faceted intervention. Interventions were provided in a variety of settings. Interventions were delivered by healthcare professionals such as general physicians, pharmacists and geriatricians, and all were conducted in high-income countries. Assessments using the Cochrane 'Risk of bias' tool, found that there was a high and/or unclear risk of bias across a number of domains. Based on the GRADE approach, the overall certainty of evidence for each pooled outcome ranged from low to very low.It is uncertain whether pharmaceutical care improves medication appropriateness (as measured by an implicit tool), mean difference (MD) -4.76, 95% CI -9.20 to -0.33; 5 studies, N = 517; very low-certainty evidence). It is uncertain whether pharmaceutical care reduces the number of potentially inappropriate medications (PIMs), (standardised mean difference (SMD) -0.22, 95% CI -0.38 to -0.05; 7 studies; N = 1832; very low-certainty evidence). It is uncertain whether pharmaceutical care reduces the proportion of patients with one or more PIMs, (risk ratio (RR) 0.79, 95% CI 0.61 to 1.02; 11 studies; N = 3079; very low-certainty evidence). Pharmaceutical care may slightly reduce the number of potential prescribing omissions (PPOs) (SMD -0.81, 95% CI -0.98 to -0.64; 2 studies; N = 569; low-certainty evidence), however it must be noted that this effect estimate is based on only two studies, which had serious limitations in terms of risk bias. Likewise, it is uncertain whether pharmaceutical care reduces the proportion of patients with one or more PPOs (RR 0.40, 95% CI 0.18 to 0.85; 5 studies; N = 1310; very low-certainty evidence). Pharmaceutical care may make little or no difference in hospital admissions (data not pooled; 12 studies; N = 4052; low-certainty evidence). Pharmaceutical care may make little or no difference in quality of life (data not pooled; 12 studies; N = 3211; low-certainty evidence). Medication-related problems were reported in eight studies (N = 10,087) using different terms (e.g. adverse drug reactions, drug-drug interactions). No consistent intervention effect on medication-related problems was noted across studies.

AUTHORS' CONCLUSIONS

It is unclear whether interventions to improve appropriate polypharmacy, such as reviews of patients' prescriptions, resulted in clinically significant improvement; however, they may be slightly beneficial in terms of reducing potential prescribing omissions (PPOs); but this effect estimate is based on only two studies, which had serious limitations in terms of risk bias.

Drug-drug Interactions in Psychiatric Practice, Part 1: Reasons, Importance, and Strategies to Avoid and Recognize Them

This column begins a series exploring drug-drug interactions (DDIs) with a special emphasis on psychiatric medications. As explained in this column, this topic is important for multiple reasons. First, a large percentage of the population is receiving psychiatric medications. Second, these patients are likely to be on multiple medications which means that they are at risk for an adverse DDI. Third, DDIs may occur but not be recognized even though they have significant health care consequences for the patient. Fourth, these consequences can range from a catastrophic outcome to more everyday clinical problems involving a myriad of presentations as enumerated in this column. Also discussed in this column is the fact that all drugs, including psychiatric medications, interact on the basis of their pharmacodynamics and pharmacokinetics rather than their therapeutic use. Therefore, psychiatric medications may interact with medications prescribed for nonpsychiatric reasons as well as with other psychiatric medications. Tables are included that explain reasons for multiple medication use and principles to follow to minimize the risk of adverse DDIs.

Potential Clinical and Economic Impact of Switching Branded Medications to Generics

Switching branded to generic medications has become a common cost-containment measure. Although this is an important objective for health care systems worldwide, the impact of this practice on patient outcomes needs to be carefully considered. We reviewed the literature summarizing the potential clinical and economic consequences of switching from branded to generic medications on patient outcomes. A literature search of peer-reviewed articles published 2003-2013 using key words of "generic switching" or "substitution" was conducted using PubMed, OvidSP, and ScienceDirect. Of 30 articles identified and reviewed, most were related to the diseases of the central nervous system, especially epilepsy. Based on our review, potential impacts of switching fell into 3 broad categories: patient attitudes and adherence, clinical and safety outcomes, and cost and resource utilization. Although in many cases generics may represent an appropriate alternative to branded products, this may not always be the case. Specifically, several studies suggested that switching may negatively impact medication adherence, whereas other studies found that generic switching was associated with poorer clinical outcomes and more adverse events. In some instances, switching accomplished cost savings but did so at increased total cost of care because of increased physician visits or hospitalizations. Although in many cases generics may represent an appropriate alternative, mandatory generic switching may lead to unintended consequences, especially in certain therapeutic areas. Although further study is warranted, based on our review, it may be medically justifiable for physicians and patients to retain the right to request the branded product in certain cases.

The moderating and covarying effects of social support and pain intensity on depressive symptomology among racially and ethnically diverse older adults

Aim: To examine the interplay of social support, pain intensity and ethnicity as moderators and covariates of relationship on depressive symptomatology. Methods: Racially and ethnically diverse elders responded to measures of depressive symptomatology and social support. Results: Hispanics reported significantly higher prevalence of moderate pain intensity and depressive symptomology, and lower prevalence of high social support compared with other ethnic groups. Although social support showed reduced depressive symptomatology among those with high pain intensity, it did not play a significant role in decreasing depressive symptomatology among those with low/moderate pain intensity. Conclusion: Social support in decreasing depressive symptomatology is more effective in older adults with high pain intensity than those with moderate or low levels of pain intensity.

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.

Prediction of individual response to antidepressants and antipsychotics: an integrated concept

In both clinical trials and daily practice, there can be substantial inter- and even intraindividual variability in response--whether beneficial or adverse--to antidepressants and antipsychotic medications. So far, no tools have become available to predict the outcome of these treatments in specific patients. This is because the causes of such variability are often not known, and when they are, there is no way of predicting the effects of their various potential combinations in an individual. Given this background, this paper presents a conceptual framework for understanding known factors and their combinations so that eventually clinicians can better predict what medication(s) to select and at what dose they can optimize the outcome for a given individual. This framework is flexible enough to be readily adaptable as new information becomes available. The causes of variation in patient response are grouped into four categories: (i) genetics; (ii) age; (iii) disease; and (iv) environment (internal). Four cases of increasing complexity are used to illustrate the applicability of this framework in a clinically relevant way In addition, this paper reviews tools that the clinician can use to assess for and quantify such inter- and intraindividual variability. With the information gained, treatment can be adjusted to compensate for such variability, in order to optimize outcome. Finally, the limitations of existing antidepressant and antipsychotic therapy and the way they reduce current ability to predict response is discussed.

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.

How the Probability and Potential Clinical Significance of Pharmacokinetically Mediated Drug-Drug Interactions Are Assessed in Drug Development: Desvenlafaxine as an Example

OBJECTIVE

The avoidance of adverse drug-drug interactions (DDIs) is a high priority in terms of both the US Food and Drug Administration (FDA) and the individual prescriber. With this perspective in mind, this article illustrates the process for assessing the risk of a drug (example here being desvenlafaxine) causing or being the victim of DDIs, in accordance with FDA guidance.

DATA SOURCES/STUDY SELECTION

DDI studies for the serotonin-norepinephrine reuptake inhibitor desvenlafaxine conducted by the sponsor and published since 2009 are used as examples of the systematic way that the FDA requires drug developers to assess whether their new drug is either capable of causing clinically meaningful DDIs or being the victim of such DDIs. In total, 8 open-label studies tested the effects of steady-state treatment with desvenlafaxine (50-400 mg/d) on the pharmacokinetics of cytochrome (CYP) 2D6 and/or CYP 3A4 substrate drugs, or the effect of CYP 3A4 inhibition on desvenlafaxine pharmacokinetics. The potential for DDIs mediated by the P-glycoprotein (P-gp) transporter was assessed in in vitro studies using Caco-2 monolayers.

DATA EXTRACTION

Changes in area under the plasma concentration-time curve (AUC; CYP studies) and efflux (P-gp studies) were reviewed for potential DDIs in accordance with FDA criteria.

RESULTS

Desvenlafaxine coadministration had minimal effect on CYP 2D6 and/or 3A4 substrates per FDA criteria. Changes in AUC indicated either no interaction (90% confidence intervals for the ratio of AUC geometric least-squares means [GM] within 80%-125%) or weak inhibition (AUC GM ratio 125% to < 200%). Coadministration with ketoconazole resulted in a weak interaction with desvenlafaxine (AUC GM ratio of 143%). Desvenlafaxine was not a substrate (efflux ratio < 2) or inhibitor (50% inhibitory drug concentration values > 250 μM) of P-gp.

CONCLUSIONS

A 2-step process based on FDA guidance can be used first to determine whether a pharmacokinetically mediated interaction occurs and then to assess the potential clinical significance of the DDI. In the case of the drug tested in this series of studies, the potential for clinically meaningful DDIs mediated by CYP 2D6, CYP 3A4, or P-gp was found to be low.

Interventions to improve the appropriate use of polypharmacy for older people

BACKGROUND

Inappropriate polypharmacy is a particular concern in older people and is associated with negative health outcomes. Choosing the best interventions to improve appropriate polypharmacy is a priority, hence interest in appropriate polypharmacy, where many medicines may be used to achieve better clinical outcomes for patients, is growing.

OBJECTIVES

This review sought to determine which interventions, alone or in combination, are effective in improving the appropriate use of polypharmacy and reducing medication-related problems in older people.

SEARCH METHODS

In November 2013, for this first update, a range of literature databases including MEDLINE and EMBASE were searched, and handsearching of reference lists was performed. Search terms included 'polypharmacy', 'medication appropriateness' and 'inappropriate prescribing'.

SELECTION CRITERIA

A range of study designs were eligible. Eligible studies described interventions affecting prescribing aimed at improving appropriate polypharmacy in people 65 years of age and older in which a validated measure of appropriateness was used (e.g. Beers criteria, Medication Appropriateness Index (MAI)).

DATA COLLECTION AND ANALYSIS

Two review authors independently reviewed abstracts of eligible studies, extracted data and assessed risk of bias of included studies. Study-specific estimates were pooled, and a random-effects model was used to yield summary estimates of effect and 95% confidence intervals (CIs). The GRADE (Grades of Recommendation, Assessment, Development and Evaluation) approach was used to assess the overall quality of evidence for each pooled outcome.

MAIN RESULTS

Two studies were added to this review to bring the total number of included studies to 12. One intervention consisted of computerised decision support; 11 complex, multi-faceted pharmaceutical approaches to interventions were provided in a variety of settings. Interventions were delivered by healthcare professionals, such as prescribers and pharmacists. Appropriateness of prescribing was measured using validated tools, including the MAI score post intervention (eight studies), Beers criteria (four studies), STOPP criteria (two studies) and START criteria (one study). Interventions included in this review resulted in a reduction in inappropriate medication usage. Based on the GRADE approach, the overall quality of evidence for all pooled outcomes ranged from very low to low. A greater reduction in MAI scores between baseline and follow-up was seen in the intervention group when compared with the control group (four studies; mean difference -6.78, 95% CI -12.34 to -1.22). Postintervention pooled data showed a lower summated MAI score (five studies; mean difference -3.88, 95% CI -5.40 to -2.35) and fewer Beers drugs per participant (two studies; mean difference -0.1, 95% CI -0.28 to 0.09) in the intervention group compared with the control group. Evidence of the effects of interventions on hospital admissions (five studies) and of medication-related problems (six studies) was conflicting.

AUTHORS' CONCLUSIONS

It is unclear whether interventions to improve appropriate polypharmacy, such as pharmaceutical care, resulted in clinically significant improvement; however, they appear beneficial in terms of reducing inappropriate prescribing.

Selegiline Transdermal System: An Examination of the Potential for CYP450-Dependent Pharmacokinetic Interactions With 3 Psychotropic Medications

Selegiline transdermal system (STS) is a recently approved monoamine oxidase inhibitor antidepressant. This article reports results from 3 studies examining the potential for cytochrome P450-dependent pharmacokinetic interactions between STS and 3 psychotropic medications that might be coadministered. Three open-label, randomized, Latin square, 3-sequence crossover design studies were conducted with healthy volunteers to determine the pharmacokinetic parameters of STS 6 mg/24 h and test drug (alprazolam, olanzapine, or risperidone) when administered alone and concomitantly. All pharmacokinetic parameters of interest were unaltered following selegiline or test drug monotherapy when compared to concomitant therapy. This was confirmed by least squares mean ratios and their 90% confidence intervals of log(e)-transformed C(max) and AUC(tau) values, using either standard bioequivalence criteria of 80% to 125% or study-defined 70% to 143% boundary criteria. These results demonstrate that STS 6 mg/24 h may provide an antidepressant option that is unlikely to result in CYP450-mediated pharmacokinetic drug-drug interactions.

Interventions to improve the appropriate use of polypharmacy for older people

BACKGROUND

Inappropriate polypharmacy is a particular concern in older people and is associated with negative health outcomes. Choosing the best interventions to improve appropriate polypharmacy is a priority, hence there is growing interest in appropriate polypharmacy, where many medicines may be used to achieve better clinical outcomes for patients.

OBJECTIVES

This review sought to determine which interventions alone, or in combination, are effective in improving the appropriate use of polypharmacy and reducing medication-related problems in older people.

SEARCH METHODS

A range of literature databases including MEDLINE and EMBASE were searched in addition to handsearching reference lists. Search terms included polypharmacy, Beers criteria, medication appropriateness and inappropriate prescribing.

SELECTION CRITERIA

A range of study designs were eligible. Eligible studies described interventions affecting prescribing aimed at improving appropriate polypharmacy in people aged 65 years and older where a validated measure of appropriateness was used (e.g. Beers criteria or Medication Appropriateness Index - MAI).

DATA COLLECTION AND ANALYSIS

Three authors independently reviewed abstracts of eligible studies, extracted data and assessed risk of bias of included studies. Study specific estimates were pooled, using a random-effects model to yield summary estimates of effect and 95% confidence intervals.

MAIN RESULTS

Electronic searches identified 2200 potentially relevant citations, of which 139 were examined in detail. Following assessment, 10 studies were included. One intervention was computerised decision support and nine were complex, multifaceted pharmaceutical care provided in a variety of settings. Appropriateness of prescribing was measured using the MAI score postintervention (seven studies) and/or Beers criteria (four studies). The interventions included in this review demonstrated a reduction in inappropriate medication use. A mean difference of -6.78 (95% CI -12.34 to -1.22) in the change in MAI score in favour of the intervention group (four studies). Postintervention pooled data (five studies) showed a mean reduction of -3.88 (95% CI -5.40 to -2.35) in the summated MAI score and a mean reduction of -0.06 (95% CI -0.16 to 0.04) in the number of Beers drugs per patient (three studies). Evidence of the effect of the interventions on hospital admissions (four studies) was conflicting. Medication-related problems, reported as the number of adverse drug events (three studies), reduced significantly (35%) postintervention.

AUTHORS' CONCLUSIONS

It is unclear if interventions to improve appropriate polypharmacy, such as pharmaceutical care, resulted in a clinically significant improvement; however, they appear beneficial in terms of reducing inappropriate prescribing and medication-related problems.

Antidepressant treatment and altered CYP2D6 activity: are pharmacokinetic variations clinically relevant?

BACKGROUND

Many currently used antidepressants are substrates of the cytochrome P450 (CYP) 2D6 enzyme. In patients who experience variations in the activity of this enzyme (e.g., CYP2D6 poor and ultrarapid metabolizers [PMs and UMs]), whether caused by genetic polymorphisms or concomitant administration of a CYP2D6 inhibitor (i.e., phenoconversion), the pharmacokinetics, and hence the effects, of CYP2D6 substrate antidepressants can be altered.

METHODS

This literature review describes the clinical and empirical evidence indicating that alterations in CYP2D6 activity can negatively affect treatment outcomes in patients receiving antidepressant pharmacotherapies that are CYP2D6 substrates.

RESULTS

Based on results from a small, prospective trial, a population analysis, and a pooled analysis, CYP2D6 PMs treated with agents dependent on CYP2D6 metabolism to form an active metabolite can experience a decline in antidepressant effect. Based on a population analysis and two case studies, CYP2D6 UMs treated with antidepressants that are CYP2D6 substrates and administered in a pharmacologically active form do not experience an antidepressant effect due to the agent being too rapidly eliminated from the body. Conversely, based on prospective trials, population analyses, and case studies, phenotypic and phenoconverted CYP2D6 PMs can experience an increase in concentration-dependent adverse events due to the agent being eliminated too slowly from the body.

CONCLUSIONS

Despite these examples, few large-scale, prospective trials exploring the effect of altered CYP2D6 metabolism on antidepressant outcomes have been conducted. Future clinical trials of CYP2D6-dependent antidepressants should be designed to allow for stratification of treatment outcomes by CYP2D6 metabolizer status.

Automatic generic substitution: losing the right medication for the right patient

Traditionally, doctors have been encouraged to prescribe drugs using their generic names. Increasing cost constraints in both primary and secondary care have resulted in the Department of Health considering the introduction of ‘automatic generic substitution’ from 2010. Thus pharmacists receiving a prescription for a brand-named drug would automatically substitute it for a generic preparation where that was available. It is unlikely that the prescribing clinician would be notified of the substitution, and the patient would not be able to choose to receive his/her original medication.

Comparison of the pharmacokinetics of venlafaxine extended release and desvenlafaxine in extensive and poor cytochrome P450 2D6 metabolizers

BACKGROUND

The goal of this study was to evaluate the impact of cytochrome P450 2D6 extensive metabolizer (EM) or poor metabolizer (PM) status on the pharmacokinetics of single doses of venlafaxine extended release (ER) and desvenlafaxine (administered as desvenlafaxine succinate) in healthy adults.

METHODS

In an open-label, crossover study, 14 healthy volunteers (aged 18-55 years; 7 EMs and 7 PMs) received, in randomized sequence, single doses of venlafaxine ER 75 mg/d or desvenlafaxine 100 mg/d. Cytochrome P450 2D6 genotyping was performed, and plasma drug levels were measured. The arithmetic means and standard deviation (SD) for area under the plasma concentration-versus-time curve (AUC) and peak plasma concentration (Cmax) were calculated. Comparisons of AUC and Cmax between cytochrome P450 2D6 EMs and PMs were calculated using a Wilcoxon exact test.

RESULTS

After administration of venlafaxine ER, mean Cmax and AUC of venlafaxine were significantly greater in PMs compared with EMs, whereas mean Cmax and AUC of its metabolite, desvenlafaxine, were significantly lower for PMs than for EMs (P = 0.001, all comparisons). In contrast, mean Cmax and AUC of desvenlafaxine after administration of desvenlafaxine were comparable between EMs and PMs.

CONCLUSIONS

Cytochrome P450 2D6 genetic polymorphisms had no discernible impact on exposure to desvenlafaxine after desvenlafaxine administration; in contrast, compared with an EM phenotype, a PM phenotype had a significant effect on venlafaxine and desvenlafaxine plasma concentrations after venlafaxine ER administration. This reduced pharmacokinetic variability of desvenlafaxine may translate into better uniformity of response for patients receiving desvenlafaxine versus venlafaxine, but additional studies are required to test this hypothesis.

Effect of desvenlafaxine on the cytochrome P450 2D6 enzyme system

BACKGROUND

The cytochrome P450 2D6 (CYP2D6) enzyme is responsible for metabolizing approximately 25% of pharmaceutical agents. Individuals with impaired CYP2D6 metabolism and those concomitantly receiving agents that inhibit CYP2D6 can have variations in concentrations of such medications and their metabolites.

METHODS

Five studies assessing the interaction between desvenlafaxine and CYP2D6 are reviewed. Study 1 compared desvenlafaxine area under the plasma concentration-versus-time curve (AUC) in CYP2D6 extensive metabolizers (EMs) and poor metabolizers (PMs) after administration of 100 mg of desvenlafaxine or 75 mg of venlafaxine extended release (ER). Studies 2 to 5 assessed the effect of concomitant administration of desvenlafaxine 100 mg (studies 2, 4, and 5) or 400 mg (study 3), paroxetine (20 mg, study 4), and duloxetine (30 mg twice daily; study 5) on the CYP2D6 probe desipramine.

RESULTS

In study 1, there was no significant difference in mean desvenlafaxine AUC between the CYP2D6 EMs and PMs (-11%; P=0.641) who were administered desvenlafaxine. However, PMs receiving venlafaxine ER had significantly higher venlafaxine and lower desvenlafaxine AUCs compared with EMs (+350% and -74%, respectively; P<0.001 for each). In studies 2, 4, and 5, the mean increases in desipramine AUC with concomitant administration of desvenlafaxine 100 mg ranged from 17% to 36%; the increase with concomitant administration of desvenlafaxine 400 mg (study 3) was 90%. Paroxetine and duloxetine produced increases in mean desipramine AUC of 419% and 122%, respectively, which were significantly greater than the increases seen with desvenlafaxine 100 mg (P<0.001 for each comparison).

CONCLUSIONS

Based on the findings presented here, desvenlafaxine is expected to have a low risk for variability in efficacy and safety/tolerability resulting from CYP2D6 polymorphisms or drug-drug interactions when coadministered with CYP2D6 substrates or inhibitors.

Co-prescription of antidepressants with other psychotropics: Distinct profile of escitalopram

Objective. Recent meta-analyses have argued that there are no clinically significant differences between various selective serotonin reuptake inhibitors (SSRIs) or between SSRIs and other antidepressants. Analysis of large-scale national prescription databases may offer a unique opportunity to see whether this premise holds true in actual practice. National databases however, should be viewed with caution as they reveal only limited information about efficacy and tolerability. Methods. The number of antidepressants prescribed annually (October 2004 to September 2005), as well as the class of drug and the use of any additional psychotropics were obtained from the Israeli subsidiary of Intercontinental Marketing Services (IMS) Health. Results. During the 12-month study period there were 2,107,763 prescriptions of antidepressants reported by IMS in Israel. Compared to other drug classes, the SSRIs were used significantly more often as a sole therapy (chi-square=1343, df=3, P<0.0001). Of the SSRIs, escitalopram was the most frequently prescribed (79%) as monotherapy, followed by fluoxetine with 72% and <70% for the other SSRIs. The most frequently prescribed additional psychotropic was a benzodiazepine, in the range of 38 to nearly 50%. Conclusion. Antidepressants vary significantly in their use as a single ("monotherapy") drug. The use of additional psychotropics could reflect either the presence of symptoms not well covered by a particular antidepressant or for addressing side effects particular to a certain class of antidepressants.The premise that all SSRIs are equal is not reflected in this current examination.

Potential drug–drug interactions within Veterans Affairs medical centers

PURPOSE

This study assessed the prevalence of 25 clinically important drug-drug interactions (DDIs) in the ambulatory care clinics of the Department of Veterans Affairs medical centers (VAMCs).

METHODS

This study was a retrospective, cross-sectional database analysis of pharmacy records to assess the prevalence of 25 clinically important DDIs. For each DDI, the object drug was defined as the medication that has its therapeutic effect modified by the drug interaction process. The precipitant drug was defined as the medication responsible for affecting the pharmacologic action or the pharmacokinetic properties of the object drug. Rates of interactions for each VAMC facility were calculated as the number of patients with a DDI divided by the total number of individual patients exposed to the object or precipitant medications. The 25 DDIs were categorized into four main categories on the basis of the therapeutic classification of the medications involved in the drug pairs.

RESULTS

The study population included 2,795,345 patients who filled prescriptions for medications involved in potential DDIs across 128 VAMCs. The highest DDI exposure rate was 129.2 per 1,000 recipients of monoamine oxidase inhibitors (MAOIs) that occurred with combinations of selective serotonin-reuptake inhibitors (SSRIs). The lowest DDI exposure rate was 0.01 per 1,000 warfarin recipients who had the warfarin and sulfinpyrazone combination.

CONCLUSION

The analysis of pharmacy records of veterans who filled prescriptions at the outpatient settings within VAMC found an overall rate of 2.15% for potential DDIs. Case-exposure rates were greatest for veterans receiving SSRIs and MAOIs, ganciclovir and zidovudine, anticoagulants and thyroid hormones, and warfarin and nonsteroidal antiinflammatory drugs.

Polypharmacy: when is it rational?

In this article, the authors discuss when it makes sense to consider using more than one medication to treat a single condition. They give a brief history of the use of polypharmacy in psychiatry and discuss how new discoveries in psychotropic drug development are making polypharmacy an increasingly important topic today. The authors then present a list of 10 criteria to guide the rational use of psychotropic polypharmacy and explain each in detail with examples drawn from clinical practice.

Comparison of duloxetine, escitalopram, and sertraline effects on cytochrome P450 2D6 function in healthy volunteers

This study is the first to directly compare the relative effects of duloxetine, escitalopram, and sertraline on the functional activity of the drug-metabolizing cytochrome P450 2D6 enzyme as assessed by changes in the pharmacokinetics of the cytochrome P450 2D6 model substrate drug, metoprolol. Single-dose pharmacokinetics of metoprolol were measured before and after 17 days of treatment with escitalopram 20 mg/d, duloxetine 60 mg/d, or sertraline 100 mg/d in young healthy male and female participants. The outcome measures were changes in metoprolol peak plasma levels, area under the plasma concentration-time curve, and clearance. The results were tested using paired t tests and independent t tests. The addition of each drug produced statistically significant changes in metoprolol pharmacokinetics. The rank order for the change in metoprolol area under the plasma concentration-time curve was duloxetine (180%) > escitalopram (89%) > sertraline (48% and 67%). Compared with sertraline, duloxetine produced statistically significantly larger changes in metoprolol pharmacokinetic parameters. The changes produced by escitalopram and sertraline were not statistically different.

The potential for clinically significant drug-drug interactions involving the CYP 2D6 system: effects with fluoxetine and paroxetine versus sertraline

BACKGROUND

Patients taking antidepressants are more likely to also be taking multiple medications, increasing the risk of adverse drug-drug interactions (DDIs). Because of substantial inhibition of one or more cytochrome P450 (CYP) enzymes at therapeutic doses, the selective serotonin reuptake inhibitors fluoxetine, fluvoxamine, and paroxetine have a higher risk of CYP-mediated DDIs than citalopram, escitalopram, and sertraline, which do not substantially inhibit any CYP enzyme.

METHODS

Prescribing patterns in 2,779 Veterans Affairs (VA) patients who had a prescription for an antidepressant in the preceding year and a current prescription for at least one systemically active drug were analyzed to determine 1) prevalence of drug combinations with potential to cause CYP-mediated DDIs, 2) frequency of combinations of fluoxetine, paroxetine, or sertraline with drugs whose metabolism is principally dependent on CYP 2D6, and 3) use of reduced doses of CYP 2D6 substrate/drugs with narrow therapeutic indices in patients on fluoxetine or paroxetine compared with sertraline.

RESULTS

In 2,779 patients, 55 pairs of drugs with the potential to cause CYP-mediated DDIs occurred in 300 patients (11%), but only 26 of the patients and 6 of the drug pairs were identified by the VA Drug Alert System. Of the 461 patients receiving fluoxetine and/or paroxetine, 39 (8%) were also receiving a CYP 2D6-model substrate/drug with a narrow therapeutic index, 14 (36%) of whom were receiving high enough doses to be at moderate to high risk of a serious DDI.

CONCLUSIONS

VA patients on fluoxetine, paroxetine, and sertraline were equally likely to be on drugs whose metabolism is dependent on CYP 2D6, including drugs with narrow therapeutic indices. No differences were found in doses of tricyclic antidepressants (i.e., "victim" drugs), which have narrow therapeutic indices and serious dose-dependent toxicity, when co-prescribed with fluoxetine or paroxetine versus sertraline (i.e., "perpetrator" drugs), despite predictable differences in CYP 2D6-mediated clearance of these drugs.

Pharmacogenomics, informatics, and individual drug therapy in psychiatry: past, present and future

The modern era of psychopharmacology began in the 10 year period from the late 1940s to the late 1950s. During this period, the first antidepressants, antipsychotics, anxiolytics and mood stabilizers were all discovered. In the 1960s, the pharmacology of these drugs was elucidated and theories about the mechanisms of action proposed. In the 1970s and 1980s, new, more selective compounds were developed based on improved structure-activity relationships derived from in vitro receptor binding studies and animal models. These compounds entered clinical testing in the 1980s and began to be marketed in the late 1980s and 1990s. All of these agents were approved to treat psychiatric syndromes which are conditions defined by a cluster of signs and symptoms. None of these agents was developed based on an understanding of the pathophysiology of the illnesses being treated. None of these agents are curative and virtually all have limited clinical efficacy. In the earliest days of the modern era, there were few drugs available to combine and many had such broad actions that they were often marginally tolerated or unsafe when used in combination (tricyclic antidepressants and monoamine oxidase inhibitors). With the advent of more medications, the frequency and extent of polypharmacy has exploded. In addition to simply having more drugs from which to select with different pharmacological profiles, many newer medications are also more selective in their pharmacological actions and thus are often better tolerated and safer when used in combination. In addition, there is the concern that the trade-off for more selective pharmacology may have been better tolerability at the expense of reduced efficacy, which clinicians then compensate for by using more medications in combination. For all of the above reasons, polypsychopharmacology has been present from the beginning of the modern era of psychopharmacotherapy and continues to be the rule rather than the exception. In fact, the frequency and the complexity of such polypsychopharmacology are both enormous and increasing. The percentage of patients being discharged from the Biological Branch of the National Institute of Mental Health on more than three psychiatric medications increased more than ten times between 1974-79, and 1990-95. The majority of patients seen in the Veterans Administration Medical System in the United States are on unique combinations of medications and the frequency and complexity of such polypharmacotherapy is increased in patients on psychiatric medications. Throughout the modern era, there have been attempts to determine whether there are populations of patients selectively responsible to specific agents (e.g. serotonin versus norepinephrine reuptake inhibitors). However, no compelling data have so far emerged. Instead, clinicians generally resort to combining drugs on the basis of symptoms such as psychosis and depression or anxiety and depression. Science has primarily informed the clinician about safety concerns rather than efficacy concerns when using such combinations. That will change in the future with a better understanding of the pathophysiology of psychiatric illnesses which in turn will lead to improved therapies and the potential for more rationally derived combination treatments.

Pharmacokinetics of Fluoxetine in Elderly Men and Women

Fluoxetine is widely prescribed as an antidepressant for geriatric patients. Despite a large scientific literature describing its efficacy and safety, there are few published data describing the pharmacokinetics of fluoxetine in the elderly. Given the common practice of polypharmacy in this population, additional pharmacokinetic information in elderly men and women is needed so that physicians can better assess potential drug-drug interactions. Twenty-five subjects, men and women between ages 65 and 83, received 20 mg of fluoxetine for 1 week followed by 40 mg for 5 weeks. Serum fluoxetine levels were measured during the period of drug administration and for 8 weeks after. The plasma concentration of fluoxetine and norfluoxetine in our subjects was higher than previously reported in the literature. Elderly women had a significantly higher serum level of norfluoxetine than men. The terminal half-life of norfluoxetine was longer in patients over age 75; elderly women had a significantly slower rate of norfluoxetine elimination than similarly aged men.

Complexity of medication use in the Veterans Affairs healthcare system: Part I: Outpatient use in relation to age and number of prescribers

CONTEXT

Multiple medication use is associated with an increased incidence of adverse drug-drug interactions (DDIs), medication errors, noncompliance, hospitalization, and healthcare costs. Drugs acting systemically or gastrointestinally ("SG" drugs) are of particular concern because of their potential to interact. A better understanding is needed of the relationship between multiple medication use, particularly of SG drugs, and age, number of prescribers, and common drug regimens.

OBJECTIVE

to determine the levels of multiple SG medication use in relation to age, number of prescribers, and common drug regimens in an outpatient population served by U.S. Veterans Integrated Service Network 15 (VISN 15).

DESIGN, SETTING, AND PARTICIPANTS

cross-sectional analysis of the subset of 5,003 currently active patients from a stratified random sample of 7,000 potentially active outpatients (1,000 each from 7 sites comprising VISN 15) selected from the prescription database on a single day.

MAIN OUTCOME MEASURES

number of SG drugs/patient; number and frequency of SG drug entities and regimens.

RESULTS

Most patients (97%) were dispensed at least one SG drug: 80% received > or =2 SG drugs, of which 42% received 2-4 SG drugs, 24%, 5-7 SG drugs, and 14%, > or =8 SG drugs. 394 different SG drugs were dispensed, only 88 of which occurred in 1% or more of patients. A significant increase (p < 0.0001) in level of multiple medication use occurred with increasing age and number of prescribers. Proportions of patients receiving 8 or more SG drugs approximately doubled with each additional prescriber, up to 4 or more prescribers. No drug regimen containing 2 or more drugs occurred in 1% or more of patients; 71% of patients were receiving a unique drug regimen (based on specific SG drugs without regard to dose or administration schedule).

CONCLUSIONS

The uniqueness of SG drug regimens suggests no single prescriber could have extensive clinical experience with even a small fraction of the drug regimens patients receive. These findings suggest that potential DDIs cannot be predicted based on occurrence of common drug regimens in a general patient population. A follow-up study (reported separately) investigated whether common drug regimens can be identified by selecting for a specific drug treatment (e.g., an antidepressant). The improved ability to predict DDIs is particularly relevant for psychiatric patients, who are at increased risk for DDIs because of greater frequency of multiple medication use. In addition, DDIs may present in this population in ways that mimic worsening of primary symptoms, which may lead to increased doses of the medication that is actually responsible for the problem, causing still more toxicity.