Exposure-Toxicity Relationships of Mycophenolic Acid in Adult Kidney Transplant Patients.

Mycophenolic acid is commonly prescribed in adult kidney transplant recipients for preventing graft rejection. A therapeutic target for total mycophenolic acid area under the concentration-time curve (30-60 mg h/L) has been established in adult kidney transplant recipients and widely referenced today. However, this specific target range does not adequately characterize mycophenolic acid-associated adverse effects. The primary objective of this qualitative and critical review was to characterize the exposure-toxicity relationships of mycophenolic acid in an attempt to determine whether exposure thresholds can be identified. The secondary objective was to determine the associations of clinical variables with specific adverse effects. The inclusion criteria consisted of all peer-reviewed papers in adult kidney transplant subjects (average study age > 18 years) with both exposure (area under the concentration-time curve) and toxicity data. The exclusion criteria were papers involving the pediatric population, studies lacking either area under the concentration-time curve or toxicity data, or studies with no apparent reported variations in area under the concentration-time curves. Of the 28 papers identified, inconsistent findings have been reported for the most frequently characterized adverse events of mycophenolic acid (gastrointestinal, infectious, and hematological), while promising exposure thresholds (i.e., > 40-60 mg h/L for total mycophenolic acid) have been suggested by a few studies. The roles of free mycophenolic acid exposure, mycophenolic acid metabolites, or clinical factors influencing the manifestation of the toxicities also remain to be clarified. Although it is not yet possible to define toxicity threshold(s) for the purpose of mycophenolic acid therapeutic drug monitoring, the information obtained and the limitations identified in this comprehensive literature body have provided a good foundation for future investigations.

What Is the Evidence for Co-trimoxazole, Clindamycin, Doxycycline, and Minocycline in the Treatment of Methicillin-Resistant Staphylococcus aureus (MRSA) Pneumonia?

Objective: To review the evidence for trimethoprim-sulfamethoxazole (TMP-SMX), clindamycin, doxycycline, and minocycline in the treatment of methicillin-resistant Staphylococcus aureus (MRSA) pneumonia. Data Source: MEDLINE, PubMed, EMBASE, Google, Google Scholar, Cochrane Central Register of Controlled Trials from 1946 to May 20, 2019. The search was performed with the keywords methicillin-resistant Staphylococcus aureus, MRSA, Staphylococcus aureus, pneumonia, trimethoprim, sulfamethoxazole drug combination, trimethoprim, sulfamethoxazole, TMP-SMX, co-trimoxazole, clindamycin, doxycycline, and minocycline. Data Extraction: Studies reporting the use of the above antibiotics for MRSA pneumonia treatment with clinical outcomes were included. Search parameters were limited to English language and human studies only. Data Synthesis: The search yielded 16 relevant articles: 6 TMP-SMX, 8 clindamycin, zero doxycycline, and 2 minocycline. For TMP-SMX, prospective randomized trials showed variable results; however, these studies were not specifically designed to assess MRSA pneumonia treatment. Retrospective studies with clindamycin suggested that it could be used as monotherapy or in combination with other anti-MRSA antibiotics. There was no evidence for doxycycline use, but 2 small retrospective reviews appeared to support minocycline as a treatment option. Relevance to Patient Care and Clinical Practice: These antibiotics are often used in clinical practice as potential treatment options for MRSA pneumonia. This article reviews the evidence for the clinical efficacy and safety of these agents. Conclusions: There are limited data to support use of TMP-SMX, clindamycin, doxycycline, or minocycline in MRSA pneumonia treatment. Randomized controlled trials are required to determine the effectiveness of these antibiotics. Clinicians should base their decision to use these agents on a case-by-case basis depending on clinical status and susceptibility results.

Population Pharmacokinetics of Mycophenolic Acid Co-Administered with Tacrolimus in Corticosteroid-Free Adult Kidney Transplant Patients.

BACKGROUND AND OBJECTIVE: Mycophenolic acid is commonly prescribed to adult kidney transplant recipients. Mycophenolic acid is extensively metabolized to mycophenolic acid-glucuronide (major metabolite) and mycophenolic acid-acyl-glucuronide (minor metabolite). We hypothesized that (1) adult kidney transplant patients on corticosteroid-free regimens exhibit unique mycophenolic acid population pharmacokinetics compared with patients receiving corticosteroid-based therapy, and (2) mycophenolic acid clearance is directly dependent on glucuronide metabolite formation. METHODS: Non-linear mixed-effects modeling was conducted with MonolixSuite-2018R1 (n = 27). Optimal pharmacokinetic models were selected based on objective function values, standard errors, and biological plausibility. RESULTS: Clinical demographic data were sex (female, 16), age (47 ± 13 years, mean ± standard deviation), weight (70 ± 16 kg), height (165 ± 9 cm), albumin (43 ± 4 g/L), serum creatinine (102 ± 27 µmol/L), estimated glomerular filtration rate (61 ± 16 mL/min/1.73 m2), mycophenolic acid dosage (1.4 ± 0.5 g/day, as mycophenolate mofetil), and tacrolimus dosage (5 ± 3 mg/day, immediate release). The population pharmacokinetics of mycophenolic acid can be described by a two-compartment first-order absorption with lag time, and a linear elimination structural model. The apparent oral clearance estimate in the final model (population mean, relative standard error) was 2.87 L/h, 42.3%, which is lower than that reported for similar patients on corticosteroid-based regimens (11.9-26.3 L/h). Other pharmacokinetic parameters were comparable to historical data obtained in corticosteroid-based patients. Both mycophenolic acid-acyl-glucuronide trough concentration and the area under the concentration-time curve ratio were significant covariates that reduced mycophenolic acid apparent oral clearance from 16.5 (base model) to 2.87 L/h. The model was evaluated based on bootstrapping, visual predictive checks, and diagnostic plots. CONCLUSIONS: Our novel findings suggest the potential need to reduce mycophenolic acid dosage in subjects on corticosteroid-free regimens. Corticosteroid-free subjects may also be more sensitive to drug/gene interactions.

Survey of Therapeutic Drug Monitoring Practices in Pediatric Health Care Programs across Canada.

BACKGROUND: Therapeutic drug monitoring (TDM) is helpful in situations where a drug has a narrow therapeutic index, a drug dosage does not reliably predict serum concentration, or a serum drug concentration has surrogate value (i.e., is reflective of clinical outcomes). TDM is especially important for the pediatric population, where wide variability in pharmacokinetics and differences in body composition and drug disposition exist. Unfortunately, very little is known about pediatric TDM patterns and the factors that affect the ordering of serum drug measurements. OBJECTIVES: To describe TDM practice for pediatric patients in Canada, to report on the drugs that are monitored and how they are monitored, and to discern factors that influence pediatric TDM patterns. METHODS: An electronic survey was developed with online survey software and was disseminated to 42 pediatric health care centres in Canada over the period January to March 2016. RESULTS: Of the 42 sites invited to participate in the survey, 20 (48%) responded. All sites reported performing TDM for pediatric patients, and the median number of drugs monitored was 18.5 (range 9-28) per site. The sites differed in terms of TDM practice (e.g., indications for TDM, types of serum drug measurements). Pharmacogenetic testing currently does not play a major role in TDM. Reported barriers to TDM practice include perceived lack of clinical value for certain drugs, limited access to analytical testing, and delayed return of test results. CONCLUSIONS: TDM practice is widespread in Canada. To better utilize TDM for clinical practice, future efforts can be aimed toward increasing awareness of the clinical value of TDM and improving the timeliness of access to TDM results.

CONTEXTE: Le suivi thérapeutique pharmacologique est utile dans les cas où un médicament possède un indice thérapeutique étroit, si une posologie ne permet pas d'établir de façon fiable les concentrations sériques ou si les concentrations sériques d'un médicament ont une valeur de substitution (c'est-à-dire qu'elles reflètent les résultats cliniques). Le suivi thérapeutique pharmacologique est particulièrement important pour la population pédiatrique, où il existe une grande variabilité pharmacocinétique et des différences quant à la composition corporelle et au devenir des médicaments dans l'organisme. Malheureusement, on ne connaît que peu de choses à propos des habitudes de suivi thérapeutique pharmacologique de l'enfant et des facteurs qui influencent la prescription d'examens mesurant les concentrations sériques des médicaments. OBJECTIFS: Offrir un portrait des habitudes de suivi thérapeutique pharmacologique de la population pédiatrique au Canada, faire un compte rendu des médicaments qui nécessitent un suivi et la manière dont se déroule cette surveillance et déceler les facteurs qui influencent les habitudes de suivi thérapeutique pharmacologique de l'enfant. MÉTHODES: Un sondage électronique a été mis au point à l'aide d'un logiciel de sondage en ligne puis envoyé à 42 centres de soins pédiatriques au Canada de janvier à mars 2016. RÉSULTATS: Vingt (48 %) des 42 établissements interrogés ont répondu au sondage. Tous les établissements ont indiqué réaliser des suivis thérapeutiques pharmacologiques auprès de la population pédiatrique et le nombre médian de médicaments nécessitant une surveillance était de 18,5 (écart de 9 à 28) par établissement. Les établissements présentaient des différences en ce qui a trait aux habitudes de suivi thérapeutique pharmacologique (comme les indications pour les suivis thérapeutiques pharmacologiques et les types de mesures sériques de médicaments). À ce jour, les examens pharmacogénétiques ne jouent pas un rôle important dans le suivi thérapeutique pharmacologique. Selon les répondants, des éléments faisaient obstacle à la réalisation du suivi thérapeutique pharmacologique, notamment la croyance que certains médicaments n'ont pas de valeur clinique, l'accès limité à des tests diagnostiques et les retards dans l'obtention des résultats d'examen. CONCLUSIONS: La réalisation du suivi thérapeutique pharmacologique est répandue au Canada. Afin de l'exercer de façon plus optimale dans le cadre de la pratique clinique, le personnel de la santé doit être davantage sensibilisé à la valeur clinique du suivi thérapeutique pharmacologique et il est nécessaire d'améliorer la rapidité d'accès aux résultats de ce suivi.

RELATE: Relationship of limited sampling strategy and adverse effects of mycophenolate mofetil in pediatric renal transplant patients.

MMF, a prodrug converted to the active form MPA, is an immunosuppressant used to prevent rejection in solid organ transplant recipients. MPA exposure, defined by AUC, can be estimated using limited sampling strategies (LSS). The relationship between MPA AUC and clinical outcomes has not been studied in pediatrics. The objectives were to describe the relationship of MPA AUC (estimated via LSS) with adverse effects and rates of rejection, and to compare clinical outcomes between different MPA monitoring practices. Descriptive statistics were used to summarize demographics, adverse effects, and rejection. Thirty-three patients (91 trough concentrations and 12 LSS sets) aged 2-20 years old were included. The estimated median MPA AUCs (David-Neto and Filler) were higher for those who did not have any adverse effects reported (65.85 and 85.05 mg*h/L, respectively) compared to those who had an adverse effect (60.75 and 54.2 mg*h/L, respectively). The median trough concentration when no adverse effects occurred was comparable to when adverse effects occurred. The median MPA AUC at which rejection occurred was lower than in those without rejection. The median trough concentration at which rejection occurred was higher than those without rejection (3.1 mg/L compared to 1.9 mg/L). The occurrence of adverse effects or rejection was not shown to be related to measured MPA trough or AUC outside of the target therapeutic range. The value of MPA concentration monitoring remains unclear; therefore, the practice of monitoring MPA AUC by LSS or trough concentrations should be reconsidered.

Population Pharmacokinetic Analysis of Immediate-Release Oral Tacrolimus Co-administered with Mycophenolate Mofetil in Corticosteroid-Free Adult Kidney Transplant Recipients.

BACKGROUND AND OBJECTIVE: Tacrolimus is the mainstay calcineurin inhibitor frequently administered with mycophenolic acid with or without corticosteroids to prevent graft rejection in adult kidney transplant recipients. The primary objective of this study was to develop and evaluate a population pharmacokinetic model characterizing immediate-release oral tacrolimus co-administered with mycophenolate mofetil (a pro-drug of mycophenolic acid) in adult kidney transplant recipients on corticosteroid-free regimens. The secondary objective was to investigate the effects of clinical covariates on the pharmacokinetics of tacrolimus, emphasizing the interacting effects of mycophenolic acid. METHODS: Population modeling and evaluation were conducted with Monolix (Suite-2018R1) using the stochastic approximation expectation-maximization algorithm in 49 adult subjects (a total of 320 tacrolimus whole-blood concentrations). Effects of clinical variables on tacrolimus pharmacokinetics were determined by population covariate modeling, regression modeling, and categorical analyses. RESULTS: A two-compartment, first-order absorption with a lag-time, linear elimination, and constant error model best represented the population pharmacokinetics of tacrolimus. The apparent clearance value for tacrolimus was 17.9 l/h (6.95% relative standard error) in our model, which is lower compared with similar subjects on corticosteroid-based therapy. The glomerular filtration rate had significant effects on the apparent clearance and central compartment volume of distribution. Conversely, mycophenolic acid did not affect the apparent clearance of tacrolimus. CONCLUSION: We have developed and internally evaluated a novel population pharmacokinetic model for tacrolimus co-administered with mycophenolate mofetil in corticosteroid-free adult kidney transplant patients. These findings are clinically important and provide further reasons for conducting therapeutic drug monitoring in this specific population.

Regression and Genomic Analyses on the Association Between Dose-Normalized Mycophenolic Acid Exposure and Absolute Neutrophil Count in Steroid-Free, De Novo Kidney Transplant Recipients.

BACKGROUND AND OBJECTIVES: The hematological side effects associated with mycophenolic acid (MPA) are relatively common and have severe consequences. The majority of literature data have not shown clear consistency in the MPA exposure-neutropenia relationship. We hypothesized that (i) adult de novo kidney transplant recipients who develop neutropenia have relatively higher dose-normalized MPA exposure than patients without neutropenia, and (ii) the observed neutropenia may be explained by polymorphisms in metabolism and/or transporter genes responsible for MPA disposition. METHODS: Adult kidney transplant recipients on steady-state tacrolimus and MPA, not receiving a corticosteroid, and with stable renal function were recruited for investigation at three periods post-transplant (1, 3, and 12 months; n = 21, 17, and 13, respectively). Clinical variables (age, weight, MPA daily dose, albumin, serum creatinine, absolute neutrophil count), tacrolimus and MPA concentrations (for exposure calculation), and genotypes (UGT2B7 G211T, UGT2B7 C802T, UGT1A9 T-275A, UGT1A9 T98C, MRP2 C-24T, MRP2 G1249A, OATP1B1 A388G, OATP1B1 C463A) were characterized. RESULTS: A significant inverse association between dose-normalized MPA exposure (a surrogate marker for apparent MPA clearance) and absolute neutrophil count in all three study periods (r2 ~ 0.3-0.7) was observed. No associations between characterized single nucleotide polymorphisms and MPA exposure or absolute neutrophil count were established. However, significant alterations in the minor allele frequencies of UGT2B7*2 C802T, UGT1A9 T275A, and MRP2 G1249A were evident. CONCLUSION: These findings support the clinical strategy for conducting MPA therapeutic drug monitoring in adult kidney transplant patients on steroid-free immunosuppressant therapy. The novel population genomic analysis data warrant further epidemiological investigations in a larger study sample.

Pharmacokinetics, safety, and patient acceptability of subcutaneous versus intramuscular testosterone injection for gender-affirming therapy: A pilot study.

PURPOSE: Results of a study comparing testosterone exposure and tolerability with subcutaneous versus i.m. administration are presented. METHODS: In a prospective, open-label, crossover study, adult participants already on stable i.m. testosterone gender-affirming therapy self-injected testosterone cypionate or enanthate i.m. for 3 weeks followed by subcutaneous injections for 8 weeks. Trough serum testosterone concentrations were determined weekly, and serial total serum testosterone (TST) concentrations were determined on postinjection days 1, 3, and 5 of weeks 3 and 11. Hemoglobin and alanine transaminase (ALT) levels were measured at week 3 (the first visit), with repeat measurements at week 11 (the final visit). The dose-normalized area under the time-concentration curve (AUC) was calculated during weeks 3 and 11. RESULTS: Fourteen transgender males (mean age, 30 ± 10 years) participated in the study. The mean hemoglobin values at the first and final visits were 160 ± 9 and 153 ± 9 g/L, respectively (p > 0.05); the mean ALT values were 18 ± 6 and 21 ± 10 IU/L (p > 0.05). Total testosterone exposure was comparable with subcutaneous versus i.m. injection (mean AUC, 1.7 ± 0.6 nmol·days/L/mg versus 1.9 ± 0.6 nmol·days/L/mg; p > 0.05). Information collected via weekly questionnaires indicated that the subcutaneous route was more tolerable, with lower self-reported scores for preinjection anxiety, pain during injection, and postinjection pain. CONCLUSION: The subcutaneous route for the injection of testosterone was well tolerated and appeared to be as effective as i.m. injection in delivering equivalent TST levels, although there was wide intrapatient and interpatient variability.

The Relationship Between Vancomycin Trough Concentrations and AUC/MIC Ratios in Pediatric Patients: A Qualitative Systematic Review.

BACKGROUND: In adults, the area under the concentration-time curve (AUC) divided by the minimum inhibitory concentration (MIC) is associated with better clinical and bacteriological response to vancomycin in patients with methicillin-resistant Staphylococcus aureus who achieve target AUC/MIC ≥ 400. This target is often extrapolated to pediatric patients despite the lack of similar evidence. The impracticalities of calculating the AUC in practice means vancomycin trough concentrations are used to predict the AUC/MIC. OBJECTIVE: This review aimed to determine the relationship between vancomycin trough concentrations and AUC/MIC in pediatric patients. METHODS: We searched the MEDLINE and Embase databases, the Cochrane Database of Systematic Reviews, and the Cochrane Central Register of Controlled Trials using the medical subject heading (MeSH) terms vancomycin and AUC and pediatric* or paediatric*. Articles were included if they were published in English and reported a relationship between vancomycin trough concentrations and AUC/MIC. RESULTS: Of 122 articles retrieved, 11 met the inclusion criteria. One trial reported a relationship between vancomycin trough concentrations, AUC/MIC, and clinical outcomes but was likely underpowered. Five studies found troughs 6-10 mg/l were sufficient to attain an AUC/MIC > 400 in most general hospitalized pediatric patients. One study in patients undergoing cardiothoracic surgery found a trough of 18.4 mg/l achieved an AUC/MIC > 400. Two oncology studies reported troughs ≥ 15 mg/l likely attained an AUC/MIC ≥ 400. In critical care patients: one study found a trough of 9 mg/l did not attain the AUC/MIC target; another found 7 mg/l corresponded to an AUC/MIC of 400. CONCLUSIONS: Potential vancomycin targets varied based on the population studied but, for general hospitalized pediatric patients, troughs of 6-10 mg/l are likely sufficient to achieve AUC/MIC ≥ 400. For MIC ≥ 2 mg/l, higher troughs are likely necessary to achieve an AUC/MIC ≥ 400. More research is needed to determine the relationships between vancomycin trough concentrations, AUC/MIC, and clinical outcomes.

Population Pharmacokinetics of Mycophenolic Acid: An Update.

The most recent comprehensive reviews on the population pharmacokinetics of mycophenolic acid (MPA) were published in 2014. Since then, several population pharmacokinetic studies on MPA have been published. The majority of literature is still focused on the kidney transplant population, although studies have also been conducted in liver and lung transplantation, autoimmune diseases, and hematopoietic stem cell transplant. While the majority of the model building is still based on parametric non-linear mixed-effects modeling, recent studies suggest the suitability of other methodologies. Additionally, instead of just focusing on pharmacokinetic modeling, a trend toward describing the relationships between pharmacokinetic and pharmacodynamic parameters is observed. Given the importance of enterohepatic recirculation (EHR) in the pharmacokinetics of MPA, more authors have attempted to characterize this process in their models. Overall, the recent models have become more sophisticated and incorporate EHR, pharmacodynamic relationships, and metabolites while maintaining many of the population values and covariates identified previously. However, the number of MPA population pharmacokinetic models describing the enteric-coated formulation of MPA (EC-MPA) is still limited. Given the increasing use of EC-MPA, more studies are needed to fill this literature gap. In addition, few studies are yet available characterizing free MPA concentration or MPA metabolites. Given the extensive protein binding, low to intermediate extraction, and intrinsic clearance characteristics of MPA in humans, including these variables would improve the population structural models.

Prevention and Treatment of Hyponatremia in Patients with Subarachnoid Hemorrhage: A Systematic Review.

BACKGROUND: Current guidelines for the management of hyponatremia in patients with subarachnoid hemorrhage (SAH) are not based on a systematic assessment of the literature. We evaluated published studies on the efficacy and safety of current preventative and treatment strategies for hyponatremia in patients with SAH. METHODS: We searched the Cochrane Central Register of Controlled Trials, Embase, MEDLINE, and PubMed for relevant studies. Primary outcomes of interest included neurologic functional outcomes, symptomatic vasospasm, and others. Secondary outcomes included measures of sodium and volume status. RESULTS: We included 5 out of 117 identified studies: 1 before-and-after observational trial (using fludrocortisone) and 4 randomized controlled trials (2 using fludrocortisone; 2 using hydrocortisone). All 5 trials had a high risk of bias in at least 1 domain. We could not perform a meta-analysis of functional outcomes; however, individual studies did not demonstrate statistically significant differences. Mineralocorticoid use did not statistically significantly reduce the incidence of symptomatic vasospasm (relative risk, 0.60; 95% confidence interval, 0.35-1.03; I2 = 0%). The studies did not report other primary outcomes. In the 4 RCTs, mineralocorticoid use reduced natriuresis and volume contraction. CONCLUSIONS: Current evidence does not demonstrate a benefit of preventative treatment with mineralocorticoids in clinically important outcomes, although a difference cannot be ruled out due to imprecision. Larger well-designed trials are needed to establish the impact of mineralocorticoids and fluid and sodium supplementation strategies on clinically relevant outcomes in the prevention and treatment of hyponatremia in patients with SAH.

'The bus analogy': A new analogy to help pharmacy students conceptualize the well-stirred model.

BACKGROUND AND PURPOSE: To determine whether an analogy relating a city bus to the well-stirred model for high extraction drugs administered intravenously improves pharmacy students' self-perceived and objectively-assessed understanding. EDUCATIONAL ACTIVITY AND SETTING: Fifty-two entry-to-practice pharmacy students enrolled in an elective clinical pharmacokinetics course completed a questionnaire and quiz before and after the bus analogy presentation. Pre- and post test questionnaires consisted of five items measuring (on five-point unipolar scale) students' self-perceived understanding of the model. Pre- and posttest quizzes contained one case-based question requiring mathematical, graphical, and intuitive understanding. Student's paired t-test with unequal variances was used to compare pre- and posttest results. FINDINGS: The bus analogy significantly improved students' self-perceived understanding of the model for all questionnaire items (p<0.01 each) and students' pre- and posttest mean quiz results (p<0.0001). SUMMARY: The bus analogy significantly improved pharmacy students' understanding of the well-stirred model both subjectively and objectively, and should be an adjunct to pharmacokinetics curricula.

Revolutionizing Therapeutic Drug Monitoring with the Use of Interstitial Fluid and Microneedles Technology.

While therapeutic drug monitoring (TDM) that uses blood as the biological matrix is the traditional gold standard, this practice may be impossible, impractical, or unethical for some patient populations (e.g., elderly, pediatric, anemic) and those with fragile veins. In the context of finding an alternative biological matrix for TDM, this manuscript will provide a qualitative review on: (1) the principles of TDM; (2) alternative matrices for TDM; (3) current evidence supporting the use of interstitial fluid (ISF) for TDM in clinical models; (4) the use of microneedle technologies, which is potentially minimally invasive and pain-free, for the collection of ISF; and (5) future directions. The current state of knowledge on the use of ISF for TDM in humans is still limited. A thorough literature review indicates that only a few drug classes have been investigated (i.e., anti-infectives, anticonvulsants, and miscellaneous other agents). Studies have successfully demonstrated techniques for ISF extraction from the skin but have failed to demonstrate commercial feasibility of ISF extraction followed by analysis of its content outside the ISF-collecting microneedle device. In contrast, microneedle-integrated biosensors built to extract ISF and perform the biomolecule analysis on-device, with a key feature of not needing to transfer ISF to a separate instrument, have yielded promising results that need to be validated in pre-clinical and clinical studies. The most promising applications for microneedle-integrated biosensors is continuous monitoring of biomolecules from the skin's ISF. Conducting TDM using ISF is at the stage where its clinical utility should be investigated. Based on the advancements described in the current review, the immediate future direction for this area of research is to establish the suitability of using ISF for TDM in human models for drugs that have been found suitable in pre-clinical experiments.

Impact of Genetic Polymorphisms on Phenytoin Pharmacokinetics and Clinical Outcomes in the Middle East and North Africa Region.

BACKGROUND: Genetic polymorphisms are known to influence outcomes with phenytoin yet effects in the Middle East and North Africa region are poorly understood. OBJECTIVES: The objective of this systematic review was to evaluate the impact of genetic polymorphisms on phenytoin pharmacokinetics and clinical outcomes in populations originating from the Middle East and North Africa region, and to characterize genotypic and allelic frequencies within the region for genetic polymorphisms assessed. METHODS: MEDLINE (1946-3 May, 2017), EMBASE (1974-3 May, 2017), Pharmacogenomics Knowledge Base, and Public Health Genomics Knowledge Base online databases were searched. Studies were included if genotyping and analyses of phenytoin pharmacokinetics were performed in patients of the Middle East and North Africa region. Study quality was assessed using a National Institutes of Health assessment tool. A secondary search identified studies reporting genotypic and allelic frequencies of assessed genetic polymorphisms within the Middle East and North Africa region. RESULTS: Five studies met the inclusion criteria. CYP2C9, CYP2C19, and multidrug resistance protein 1 C3435T variants were evaluated. While CYP2C9*2 and *3 variants significantly reduced phenytoin metabolism, the impacts of CYP2C19*2 and *3 variants were unclear. The multidrug resistance protein 1 CC genotype was associated with drug-resistant epilepsy, but reported impacts on phenytoin pharmacokinetics were conflicting. Appreciable variability in minor allele frequencies existed both between and within countries of the Middle East and North Africa region. CONCLUSIONS: CYP2C9 decrease-of-function alleles altered phenytoin pharmacokinetics in patients originating from the Middle East and North Africa region. The impacts of CYP2C19 and multidrug resistance protein 1 C3435T variants on phenytoin pharmacokinetic and clinical outcomes are unclear and require further investigation. Future research should focus on the clinical outcomes associated with phenytoin therapy. PROSPERO 2017: CRD42017057850.

Pharmacokinetic Interactions between Valproic Acid and Lorazepam (PIVOtAL Study): A Review of Site-Specific Practices.

BACKGROUND: Coadministration of lorazepam and valproic acid is identified by tertiary references as causing a major drug interaction that requires therapy modification and dosage adjustments. The proposed mechanism involves inhibition of lorazepam glucuronidation via direct inhibition of uridine 5'-diphosphate-glucuronosyltransferase enzymes by valproic acid. However, the clinical significance of this interaction is unclear. OBJECTIVES: To identify site-specific practices and assess clinical responses to the interaction between valproic acid and lorazepam. METHODS: A chart review was conducted for patients over 18 years of age who were admitted, from September 2008 to September 2014 inclusive, to the psychiatry or neurology service at Vancouver General Hospital, Vancouver, British Columbia, and who received concomitant valproic acid and lorazepam therapy. RESULTS: Of the 30 patients included in the chart review, 12 (40%) received an intervention. A total of 8 (27%) patients experienced an adverse drug reaction (ADR), such as drowsiness and dizziness. Seven of these 8 patients were among those who received an intervention. The mean dosage (± standard deviation) of lorazepam was 4.2 ± 1.2 mg per day among patients who experienced an ADR and less than 2 mg per day among those who did not experience an ADR. CONCLUSIONS: The current recommendation from tertiary drug references is to reduce the dose of lorazepam by 50% when this drug is coadministered with valproic acid. However, this recommendation could not be validated through an analysis of patients exposed to this interaction in the clinical setting or through a review of the literature. Further clinical and pharmacokinetic studies are required to determine whether concurrent treatment with lorazepam and valproic acid should be considered as causing a major drug interaction. Until more data are available, clinicians should remain cognizant of the potential for a drug-drug interaction and should use the lowest effective dose of lorazepam when this drug is administered concomitantly with valproic acid.

CONTEXTE: Selon des sources tertiaires, la prise concomitante de lorazépam et d'acide valproïque causerait une interaction médicamenteuse grave nécessitant un changement au traitement et des ajustements posologiques. Le mécanisme qui sous-tend cette interaction est l'inhibition de la glucuronoconjugaison du lorazépam au moyen de l'inhibition directe des enzymes uridine 5'-diphosphate glucuronosyltransférases par l'acide valproïque. Cependant, la signification clinique de cette interaction est inconnue. OBJECTIFS: Déterminer quelles sont les pratiques particulières à l'établissement hospitalier et évaluer les réponses cliniques à l'interaction entre l'acide valproïque et le lorazépam. MÉTHODES: On a mené une analyse des dossiers médicaux des patients de plus de 18 ans qui, entre septembre 2008 et septembre 2014 inclusivement, ont été admis au service de psychiatrie ou de neurologie de l'Hôpital général de Vancouver, à Vancouver en Colombie-Britannique, et ont reçu en même temps l'acide valproïque et le lorazépam. RÉSULTATS: Parmi les 30 patients dont le dossier médical a été retenu pour l'analyse, 12 (40 %) ont eu droit à une intervention. Un total de 8 (27 %) patients ont subi une réaction indésirable aux médicaments (RIM), comme de la somnolence et des étourdissements. Sept de ces 8 patients appartenaient au groupe qui a eu droit à une intervention. La dose quotidienne moyenne de lorazépam était de 4,2 ± 1,2 mg chez les patients qui ont subi une RIM et de moins de 2 mg chez ceux qui n'en ont pas subi. CONCLUSIONS: Des sources tertiaires sur les médicaments recommandent actuellement de réduire la dose de lorazépam de 50 % lorsque ce médicament est administré conjointement avec l'acide valproïque. Or, cette recommandation n'a pu être validée à l'aide d'une revue de la littérature ou d'une analyse des dossiers des patients ayant été exposés à une telle interaction médicamenteuse en milieu clinique. De plus amples études cliniques et pharmacocinétiques sont nécessaires pour déterminer si la prise concomitante de lorazépam et d'acide valproïque peut être considérée comme une cause d'interaction médicamenteuse grave. D'ici à ce qu'ils disposent de plus de données probantes, les cliniciens doivent demeurer conscients du potentiel d'interaction médicament-médicament et utiliser la plus faible dose efficace de lorazépam lorsque ce médicament est pris en concomitance avec l'acide valproïque.

Penetration of Vancomycin into the Cerebrospinal Fluid: A Systematic Review.

INTRODUCTION: Infectious disease and pharmacokinetic textbooks indicate that vancomycin has poor penetration into the central nervous system due to its hydrophilic nature and high molecular weight. Recent literature suggests that penetration of vancomycin into cerebrospinal fluid (CSF) is higher than previously reported; therefore, we conducted a systematic review to assess the penetration of vancomycin into CSF. METHODS: We searched the MEDLINE, EMBASE, and CENTRAL electronic databases for English-language human studies evaluating serum and CSF concentrations of intravenous vancomycin. RESULTS: In 13 identified studies, the CSF-to-serum ratio of vancomycin varied from 0.00 to 0.81. CSF penetration ranged 0.06-0.81 in patients with meningitis, 0.05-0.17 in ventriculitis, 0.00-0.36 in other infections, and 0-0.13 in patients without infection. Despite variable CSF penetration, 83% of patients with meningitis and 100% of patients with ventriculitis achieved clinical cure. No factor predicted vancomycin CSF penetration. CONCLUSION: Contrary to prior belief, studies included in our review did not show universally low penetration of vancomycin into CSF. CSF vancomycin levels were variable and did not predict clinical cure.

Evidence-Based Review of Pharmacotherapy Used for Parkinson's Disease Psychosis.

OBJECTIVE: To summarize and evaluate the existing literature regarding medications to treat Parkinson's disease (PD) psychosis. DATA SOURCES: MEDLINE (1946 to March 2017), EMBASE (1980 to March 2017), CINAHL (1982 to March 2017), and PsychInfo (1887 to March 2017) were searched using the following terms: Parkinson disease, Parkinson's disease, psychotic disorders, psychosis, delusions, and hallucinations. STUDY SELECTION AND DATA EXTRACTION: The search was limited to randomized controlled trials (RCTs) reporting human outcomes. Data extracted included the following: study design, population, setting, intervention, control, outcomes related to psychosis and safety, and potential biases assessed using Cochrane Collaboration's Risk of Bias Assessment Tool. DATA SYNTHESIS: After assessment, 16 of 235 studies were included; 11 articles reported comparisons between active drug and placebo, whereas 5 compared clozapine and an active comparator. Placebo-controlled trials demonstrated benefit for clozapine (n = 2) and pimavanserin (n = 2), with no firm benefits observed for quetiapine (n = 4) or olanzapine (n = 3). Comparative studies demonstrated improved efficacy in symptom scores when clozapine or comparator agent (n = 2, quetiapine; n = 1, olanzapine; n = 1, risperidone; and n = 1, ziprasidone) was assessed alone. However, no comparator data suggest that one agent is better than another, and none are yet available for pimavanserin. Overall risk of bias across all studies was moderate to high. CONCLUSIONS: Despite lack of rigor in study designs, published data to date suggest that clozapine and pimavanserin should be considered drugs of choice to treat PD psychosis.

Clinical Pharmacokinetic Monitoring of Leflunomide in Renal Transplant Recipients with BK Virus Reactivation: A Review of the Literature.

Leflunomide is an immunosuppressive drug with in vitro and initial observational evidence of antiviral activity against BK virus (BKV), a pathogen that causes opportunistic infection upon reactivation in renal transplant recipients. Leflunomide is considered an ancillary option to immunosuppression reduction in the management of BKV reactivation. Plasma or blood concentrations of teriflunomide, the active metabolite of leflunomide, are commonly monitored because of high leflunomide doses being used, known inter-individual variability in pharmacokinetics, and hepatotoxicity risk. However, the utility of clinical pharmacokinetic monitoring for leflunomide is as yet unclear. A literature search of MEDLINE (1946-December 2016), EMBASE (1974-December 2016), the CENTRAL database, and Google Scholar was performed to identify relevant English-language articles. Further articles were identified from references in relevant literature. A previously published 9-step decision-making algorithm was used to assess the available literature and determine the utility of clinical pharmacokinetic monitoring for leflunomide. Teriflunomide is readily measurable in the plasma or blood, but a clear relationship between concentration and efficacy or toxicity is lacking, and its therapeutic range is not well-established. Efficacy and toxicity endpoints such as renal function and BKV clearance can be readily assessed without measuring teriflunomide concentrations. Pharmacokinetic parameters are affected by genetic polymorphisms in cytochrome P450 CYP2C19 and ABCG2 genes. Therefore, routine clinical pharmacokinetic monitoring of leflunomide cannot be recommended based on current available evidence. However, it may provide clinical benefit in difficult situations when patients demonstrate a lack of therapeutic response or exhibit signs of drug toxicity.