Drug dosing in obese critically ill patients, a literature review

INTRODUCTION

The prevalence of obesity represents a significant global public health challenge, and the available evidence concerning the appropriate dosing of pharmaceutical in patients with obesity is limited. It is uncommon for clinical trials in critically ill patients to include obese individuals, which results in a lack of specific dosing information in product data sheets. The objective of this literature review is to provide clinicians with efficacious and secure guidelines for this cohort of patients.

METHODS

A multidisciplinary team comprising pharmacists specialized in hospital pharmacy and physicians with expertise in intensive care medicine was established. The therapeutic groups and, in particular, the most commonly used active ingredients within the Intensive Care Unit were identified and subjected to detailed analysis. The following terms were included in the search: "obese", "overweight", "critical illness", "drug dosification", and "therapeutic dose monitoring". All the information was then evaluated by the working group, which reached a consensus on the dosing recommendations for each drug in obese critically ill patients.

RESULTS

A total of 83 drugs belonging to the following therapeutic groups were identified: antivirals, antibacterials, antifungals, immunosuppressants, antiepileptics, vasopressors, anticoagulants, neuromuscular blocking agents and sedatives. A table was produced containing the consensus dosing recommendations for each of the aforementioned drugs following a review of the available evidence.

CONCLUSIONS

Drug dosing in obese patients, both in critical and noncritical settings, remains an area with significant uncertainty. This review provides comprehensive and up-to-date information on the dosing of the main therapeutic groups in obese critically ill patients, offering a valuable resource physicians in critical care units and clinical pharmacists in their practice in this setting.

Clinical Use of Super-Bioavailable Itraconazole for the Management of Dermatophytosis: Consensus Statement by Dermatologists from India via the Modified Delphi Technique

Super-bioavailable itraconazole (SB ITZ) overcomes the limitations of conventional itraconazole (CITZ) such as interindividual variability and reduced bioavailability. It has been approved for systemic mycoses in Australia and Europe as 50 mg and the USA as 65 mg and in India as 50 mg, 65 mg, 100 mg, and 130 mg. However, data on the ideal dose and duration of SB ITZ treatment in managing dermatophytosis are insufficient. This consensus discusses the suitability, dosage, duration of treatment, and relevance of using SB ITZ in managing dermatophytosis in different clinical scenarios. Sixteen dermatologists (>15 years of experience in the field and ≥2 years clinical experience with SB ITZ), formed the expert panel. A modified Delphi technique was employed, and a consensus was reached if the concordance in response was >75%. A total of 26 consensus statements were developed. The preferred dose of SB ITZ is 130 mg once daily and if not tolerated, 65 mg twice daily. The preferred duration for treating naïve dermatophytosis is 4-6 weeks and that for recalcitrant dermatophytosis is 6-8 weeks. Moreover, cure rates for dermatophytosis are a little better with SB ITZ than with CITZ with a similar safety profile as of CITZ. Better patient compliance and efficacy are associated with SB ITZ than with CITZ, even in patients with comorbidities and special needs such as patients with diabetes, extensive lesions, corticosteroid abuse, adolescents, and those on multiple drugs. Expert clinicians reported that the overall clinical experience with SB ITZ was better than that with CITZ.

Updated antimicrobial dosing recommendations for obese patients

The prevalence of obesity has increased considerably in the last few decades. Pathophysiological changes in obese patients lead to pharmacokinetic (PK) and pharmacodynamic (PD) alterations that can condition the correct exposure to antimicrobials if standard dosages are used. Inadequate dosing in obese patients can lead to toxicity or therapeutic failure. In recent years, additional antimicrobial PK/PD data, extended infusion strategies, and studies in critically ill patients have made it possible to obtain data to provide a better dosage in obese patients. Despite this, it is usually difficult to find information on drug dosing in this population, which is sometimes contradictory. This is a comprehensive review of the dosing of different types of antimicrobials (antibiotics, antifungals, antivirals, and antituberculosis drugs) in obese patients, where the literature on PK and possible dosing strategies in obese adults was critically assessed.

Candidemia in Adult Patients in the ICU: A Reappraisal of Susceptibility Testing and Antifungal Therapy

OBJECTIVE

To provide updates on the epidemiology and recommendations for management of candidemia in patients with critical illness.

DATA SOURCES

A literature search using the PubMed database (inception to March 2023) was conducted using the search terms "invasive candidiasis," "candidemia," "critically ill," "azoles," "echinocandin," "antifungal agents," "rapid diagnostics," "antifungal susceptibility testing," "therapeutic drug monitoring," "antifungal dosing," "persistent candidemia," and "Candida biofilm."

STUDY SELECTION/DATA EXTRACTION

Clinical data were limited to those published in the English language. Ongoing trials were identified through ClinicalTrials.gov.

DATA SYNTHESIS

A total of 109 articles were reviewed including 25 pharmacokinetic/pharmacodynamic studies and 30 studies including patient data, 13 of which were randomized controlled clinical trials. The remaining 54 articles included fungal surveillance data, in vitro studies, review articles, and survey data. The current 2016 Infectious Diseases Society of America (IDSA) Clinical Practice Guideline for the Management of Candidiasis provides recommendations for selecting empiric and definitive antifungal therapies for candidemia, but data are limited regarding optimized dosing strategies in critically ill patients with dynamic pharmacokinetic changes or persistent candidemia complicated.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

Outcomes due to candidemia remain poor despite improved diagnostic platforms, antifungal susceptibility testing, and antifungal therapy selection for candidemia in critically ill patients. Earlier detection and identification of the species causing candidemia combined with recognition of patient-specific factors leading to dosing discrepancies are crucial to improving outcomes in critically ill patients with candidemia.

CONCLUSIONS

Treatment of candidemia in critically ill patients must account for the incidence of non-albicans Candida species and trends in antifungal resistance as well as overcome the complex pathophysiologic changes to avoid suboptimal antifungal exposure.

Comparative Efficacy and Safety of Super-Bioavailable Itraconazole-130 mg Once Daily in Obese and Non-Obese Patients of Glabrous Tinea

Background

Obesity is considered one of the risk factors for dermatophytosis and warrants systemic therapy. Itraconazole is the most commonly used antifungal, but owing to pharmacokinetic challenges, super-bioavailable itraconazole (SITZ) was approved globally, recently. For the management of dermatophytosis in obese patients, there are mixed opinions regarding the dosing of systemic antifungals.

Materials and Methods

This study was conducted to compare the efficacy and safety of SITZ-130 mg once daily in glabrous tinea or dermatophytosis in obese and non-obese patients for a total duration of 10 weeks on 87 eligible patients. Efficacy and safety assessments were done at weeks 3 and 6 with follow-up at week 10 for relapse. The primary objective was to assess the proportion of patients achieving complete cure at week 6 with the assessment of safety, clinical, and mycological cure rates as secondary objectives.

Results

Out of 87 patients, 80 were considered for analysis. At week 6, 22/35 (63%) and 33/45 (73%) patients in obese and non-obese groups were completely cured (P = 0.47). Similarly, there was no statistically significant difference for mycological and clinical cure in both the groups (P = 0.17 and P = 0.61, respectively). Four patients in the obese group (18% of completely cured), while one patient in the non-obese group (3% of completely cured), relapsed within 4 weeks of completion of treatment (P = 0.14). The therapy was well tolerated by both groups, with only one patient in the non-obese group experiencing pruritus.

Conclusion

SITZ-130 mg once daily achieved desired and similar clinical response in obese patients as of non-obese patients suffering from dermatophytosis, and hence, a higher dose may not require in obesity.

Simultaneous Quantification of Seven Antifungal Agents in Human Serum Using Liquid Chromatography-Tandem Mass Spectrometry

Systemic antifungal agents are essential for high-risk patients undergoing immunosuppressive therapy or cancer chemotherapy because of the rapid increase in opportunistic fungal infections. Therapeutic drug monitoring is crucial to ensuring the efficacy and safety of antifungal agents owing to their pharmacokinetic variability. In the present study, we developed and validated a quantitative method for the simultaneous detection of seven commonly used antifungal drugs (amphotericin B, isavuconazole, voriconazole, fluconazole, posaconazole, caspofungin, and micafungin) using liquid chromatography-tandem mass spectrometry. Methanol (containing 0.1% formic acid) was used for protein precipitation and only 50 μL of serum was required for the analysis. Chromatographic separation was conducted using a Waters Acquity UPLC C8 column, and one stable isotope-labeled agent and two analogs were used as internal standards. The calibration curves ranged from 0.1 to 50 μg/mL for all agents, and the correlation coefficient (R2) for all calibration curves was above 0.9835. The intra-day precision (1.2-11.2%), inter-day precision (2.4-13.2%), and mean bias values (-10.9 to 13.6%) were within an acceptable range of ±15%. Successful implementation of the developed method in clinical practice would facilitate the effective monitoring of these antifungal agents.

Critical appraisal beyond clinical guidelines for intraabdominal candidiasis

BACKGROUND

Regardless of the available antifungals, intraabdominal candidiasis (IAC) mortality continues to be high and represents a challenge for clinicians.

MAIN BODY

This opinion paper discusses alternative antifungal options for treating IAC. This clinical entity should be addressed separately from candidemia due to the peculiarity of the required penetration of antifungals into the peritoneal cavity. Intraabdominal concentrations may be further restricted in critically ill patients where pathophysiological facts alter normal drug distribution. Echinocandins are recommended as first-line treatment in guidelines for invasive candidiasis. However, considering published data, our pharmacodynamic analysis suggests the required increase of doses, postulated by some authors, to attain adequate pharmacokinetic (PK) levels in peritoneal fluid. Given the limited evidence in the literature on PK/PD-based treatments of IAC, an algorithm is proposed to guide antifungal treatment. Liposomal amphotericin B is advocated as first-line therapy in patients with sepsis/septic shock presenting candidemia or endophthalmitis, or with prior exposure to echinocandins and/or fluconazole, or with infections by Candida glabrata. Other situations and alternatives, such as new compounds or combination therapy, are also analysed.

CONCLUSION

There is a critical need for more robust clinical trials, studies examining patient heterogeneity and surveillance of antifungal resistance to enhance patient care and optimise treatment outcomes. Such evidence will help refine the existing guidelines and contribute to a more personalised and effective approach to treating this serious medical condition. Meanwhile, it is suggested to broaden the consideration of other options, such as liposomal amphotericin B, as first-line treatment until the results of the fungogram are available and antifungal stewardship could be implemented to prevent the development of resistance.

The Optimal Dosing Regimen of Super Bioavailable Itraconazole in Obesity: An Experimental Rat Model Study

Background Obesity may alter tissue distribution and clearance of several drugs, especially lipophilic ones. Itraconazole, a lipophilic drug, has been recently introduced in a super-bioavailable formulation (SB-ITZ) for the treatment of dermatophytosis. Evidence regarding optimal dosing of SB-ITZ in obesity is lacking. A current experimental study was planned to analyze tissue concentrations of SB-ITZ at different doses in obese and non-obese rats.  Materials and methods Thirty-six Wistar albino rats of either sex were divided into obese and non-obese rats equally. Further, rats in both categories were divided into three dosing groups. Group 1 received SB-ITZ 13 mg once daily in the morning, group 2 received SB-ITZ 13 mg in the morning and 6.5 mg in the evening, while Group 3 rats received SB-ITZ 13 mg twice daily, orally. Concentrations of SB-ITZ in the skin, serum, and fatty tissue were assessed in each group on days 7, 14, 21, and 28. Comparison of SB-ITZ concentrations in various tissues in obese and non-obese rats and inter-group comparison of tissue concentrations across the three dosing regimens was done at day 28 and expressed as Mean ± SD.36 Wistar rats were divided into obese and non-obese rats equally. Results At day 28, skin concentrations of SB-ITZ were 5.36±1.1, 8.9±1.7 and 10.13±1.7 µg/g in Groups 1, 2, and 3, respectively, in non-obese rats, which was statistically significant (p<0.05) than skin concentration of obese rats (2.72±0.6, 4.2±0.7 and 4.66±0.5 µg/g) for the corresponding dosing groups respectively. Skin concentration of SB-ITZ was statistically significant for Groups 2 and 3 as compared to Group 1. Still, no statistically significant difference was noted between Groups 2 and 3 in non-obese and obese rats. Fatty tissue concentration of SB-ITZ was comparable in all 3 dosing regimens in non-obese and obese rats. But on the intergroup comparison, a statistically significant difference was observed for Groups 2 and 3 against Group 1 (p<0.05). Increasing the dose of SB-ITZ increased serum concentration. In non-obese rats, a statistically significant difference was noted between Group 2 (74.33±6.6 ng/ml) and Group 1 (52.5±9.9 ng/ml); p<0.01 and also in Group 3 (81.33±6.8 ng/ml) against Group 1; p<0.01. Group 3 achieved significantly higher concentration than the other two groups in obese rats (Group 3; 72±5.3, Group 2; 60.5±4.3, and Group 1; 45±7 ng/ml; p<0.01). Conclusion Overall, skin, fatty tissue, and serum concentrations of SB-ITZ were higher in non-obese rats compared to obese rats in all three dosing groups. Moreover, skin and fatty tissue concentrations were proportionately higher than serum in all the groups in non-obese and obese rats. Though the skin concentration of non-obese rats was significantly higher than obese rats, skin concentration in obese rats was within the minimum inhibitory concentration (MIC) range, demonstrating the efficacy of all dosing regimens.

Antifungal Drugs TDM: Trends and Update

PURPOSE

The increasing burden of invasive fungal infections results in growing challenges to antifungal (AF) therapeutic drug monitoring (TDM). This review aims to provide an overview of recent advances in AF TDM.

METHODS

We conducted a PubMed search for articles during 2016-2020 using "TDM" or "pharmacokinetics" or "drug-drug-interaction" with "antifungal," consolidated for each AF. Selection was limited to English language articles with human data on drug exposure.

RESULTS

More than 1000 articles matched the search terms. We selected 566 publications. The latest findings tend to confirm previous observations in real-life clinical settings. The pharmacokinetic variability related to special populations is not specific but must be considered. AF benefit-to-risk ratio, drug-drug interaction (DDI) profiles, and minimal inhibitory concentrations for pathogens must be known to manage at-risk situations and patients. Itraconazole has replaced ketoconazole in healthy volunteers DDI studies. Physiologically based pharmacokinetic modeling is widely used to assess metabolic azole DDI. AF prophylactic use was studied more for Aspergillus spp. and Mucorales in oncohematology and solid organ transplantation than for Candida (already studied). Emergence of central nervous system infection and severe infections in immunocompetent individuals both merit special attention. TDM is more challenging for azoles than amphotericin B and echinocandins. Fewer TDM requirements exist for fluconazole and isavuconazole (ISZ); however, ISZ is frequently used in clinical situations in which TDM is recommended. Voriconazole remains the most challenging of the AF, with toxicity limiting high-dose treatments. Moreover, alternative treatments (posaconazole tablets, ISZ) are now available.

CONCLUSIONS

TDM seems to be crucial for curative and/or long-term maintenance treatment in highly variable patients. TDM poses fewer cost issues than the drugs themselves or subsequent treatment issues. The integration of clinical pharmacology into multidisciplinary management is now increasingly seen as a part of patient care.

Consensus guidelines for optimising antifungal drug delivery and monitoring to avoid toxicity and improve outcomes in patients with haematological malignancy and haemopoietic stem cell transplant recipients, 2021

Antifungal agents can have complex dosing and the potential for drug interaction, both of which can lead to subtherapeutic antifungal drug concentrations and poorer clinical outcomes for patients with haematological malignancy and haemopoietic stem cell transplant recipients. Antifungal agents can also be associated with significant toxicities when drug concentrations are too high. Suboptimal dosing can be minimised by clinical assessment, laboratory monitoring, avoidance of interacting drugs, and dose modification. Therapeutic drug monitoring (TDM) plays an increasingly important role in antifungal therapy, particularly for antifungal agents that have an established exposure-response relationship with either a narrow therapeutic window, large dose-exposure variability, cytochrome P450 gene polymorphism affecting drug metabolism, the presence of antifungal drug interactions or unexpected toxicity, and/or concerns for non-compliance or inadequate absorption of oral antifungals. These guidelines provide recommendations on antifungal drug monitoring and TDM-guided dosing adjustment for selected antifungal agents, and include suggested resources for identifying and analysing antifungal drug interactions. Recommended competencies for optimal interpretation of antifungal TDM and dose recommendations are also provided.

Pharmacological management of antifungal agents in pulmonary aspergillosis: an updated review

INTRODUCTION

Aspergillus may cause different types of lung infections: invasive, chronic pulmonary or allergic bronchopulmonary aspergillosis. Pharmacological management with antifungals poses as a challenge. Patients diagnosed with pulmonary aspergillosis are complex, as well as the problems associated with antifungal agents.

AREAS COVERED

This article reviews the pharmacology of antifungal agents in development and currently used to treat pulmonary aspergillosis, including the mechanisms of action, pharmacokinetics, pharmacodynamics, dosing, therapeutic drug monitoring and safety. Recommendations to manage situations that arise in daily clinical practice are provided. A literature search of PubMed was conducted on November 15^th, 2020 and updated on March 30^th, 2021.

EXPERT OPINION

Recent and relevant developments in the treatment of pulmonary aspergillosis have taken place. Novel antifungals with new mechanisms of action that extend antifungal spectrum and improve pharmacokinetic-related aspects, drug-drug interactions and safety are under current study. For those antifungals already marketed, new data related to pharmacokinetics, pharmacodynamics, dose adjustments in special situations, therapeutic drug monitoring and safety are available. To maximize efficacy and reduce the risk of associated toxicities, it is essential to choose the most appropriate antifungal; optimize its dose, interval, route of administration and length of treatment; and prevent side effects.

Antifungal therapy with azoles and the syndrome of acquired mineralocorticoid excess

The syndromes of mineralocorticoid excess describe a heterogeneous group of clinical manifestations leading to endocrine hypertension, typically either through direct activation of mineralocorticoid receptors or indirectly by impaired pre-receptor enzymatic regulation or through disturbed renal sodium homeostasis. The phenotypes of these disorders can be caused by inherited gene variants and somatic mutations or may be acquired upon exposures to exogenous substances. Regarding the latter, the symptoms of an acquired mineralocorticoid excess have been reported during treatment with azole antifungal drugs. The current review describes the occurrence of mineralocorticoid excess particularly during the therapy with posaconazole and itraconazole, addresses the underlying mechanisms as well as inter- and intra-individual differences, and proposes a therapeutic drug monitoring strategy for these two azole antifungals. Moreover, other therapeutically used azole antifungals and ongoing efforts to avoid adverse mineralocorticoid effects of azole compounds are shortly discussed.

Influence of Body Weight Category on Outcomes in Candidemia Patients Treated With Anidulafungin

BACKGROUND

Case reports and pharmacokinetic data suggest off-label echinocandin dosing may be needed to reach adequate serum concentrations in obese patients. Few outcome studies exist evaluating this population.

OBJECTIVES

Of this study were to (1) determine the association of body mass index (BMI) with clinical outcomes of candidemia patients on standard doses of anidulafungin and (2) characterize fungal infections by body weight.

METHODS

A retrospective cohort was conducted to evaluate hospitalized patients treated for candidemia with anidulafungin at Food and Drug Administration-labeled dosing for at least 72 hours from January 1, 2014, through January 31, 2018. Candidemia was diagnosed by blood culture or T2 magnetic resonance (T2MR). Patients were compared according to BMI category.

RESULTS

One hundred seventy-three patients were included. Candida albicans and Candida glabrata were identified in 58 (33%) and 57 (33%) patients, respectively. Mortality was comparable according to BMI category: 4 (36.4%) underweight, 8 (25.8%) normal weight, 16 (32.0%) overweight, 20 (33.9%) obese, and 7 (31.8%) morbidly obese, P = .976. Variables associated with mortality included: severe sepsis (adjusted odds ratio [OR] = 5.1, 95% CI: 1.7-14.8) and liver disease (adjusted OR = 3.2, 95% CI: 1.1-9.4). Variables that were protective of mortality included: line removal (adjusted OR = 0.05, 95% CI: 0.02-0.2) and receipt of anidulafungin for at least 5 days (adjusted OR = 0.35, 95% CI: 0.15-0.8).

CONCLUSION

There was no difference detected in mortality among patients with candidemia across BMI category. Larger studies are needed to confirm whether standard doses of anidulafungin are sufficient for candidemia in obese patients.

Administration and Dosing of Systemic Antifungal Agents in Pediatric Patients

Neonates and immunosuppressed/immunocompromised pediatric patients are at high risk of invasive fungal diseases. Appropriate antifungal selection and optimized dosing are imperative to the successful prevention and treatment of these life-threatening infections. Conventional amphotericin B was the mainstay of antifungal therapy for many decades, but dose-limiting nephrotoxicity and infusion-related adverse events impeded its use. Despite the development of several new antifungal classes and agents in the past 20 years, and their now routine use in at-risk pediatric populations, data to guide the optimal dosing of antifungals in children are limited. This paper reviews the spectra of activity for approved antifungal agents and summarizes the current literature specific to pediatric patients regarding pharmacokinetic/pharmacodynamic data, dosing, and therapeutic drug monitoring.

Antifungal Drugs

We reviewed the licensed antifungal drugs and summarized their mechanisms of action, pharmacological profiles, and susceptibility to specific fungi. Approved antimycotics inhibit 1,3-β-d-glucan synthase, lanosterol 14-α-demethylase, protein, and deoxyribonucleic acid biosynthesis, or sequestrate ergosterol. Their most severe side effects are hepatotoxicity, nephrotoxicity, and myelotoxicity. Whereas triazoles exhibit the most significant drug–drug interactions, echinocandins exhibit almost none. The antifungal resistance may be developed across most pathogens and includes drug target overexpression, efflux pump activation, and amino acid substitution. The experimental antifungal drugs in clinical trials are also reviewed. Siderophores in the Trojan horse approach or the application of siderophore biosynthesis enzyme inhibitors represent the most promising emerging antifungal therapies.

Overview of antifungal dosing in invasive candidiasis

In the past, most antifungal therapy dosing recommendations for invasive candidiasis followed a 'one-size fits all' approach with recommendations for lowering maintenance dosages for some antifungals in the setting of renal or hepatic impairment. A growing body of pharmacokinetic/pharmacodynamic research, however now points to a widespread 'silent epidemic' of antifungal underdosing for invasive candidiasis, especially among critically ill patients or special populations who have altered volume of distribution, protein binding and drug clearance. In this review, we explore how current adult dosing recommendations for antifungal therapy in invasive candidiasis have evolved, and special populations where new approaches to dose optimization or therapeutic drug monitoring may be needed, especially in light of increasing antifungal resistance among Candida spp.

Pharmacokinetics of Intravenous Posaconazole in Critically Ill Patients

To date, there is no information on the intravenous (i.v.) posaconazole pharmacokinetics for intensive care unit (ICU) patients. This prospective observational study aimed to describe the pharmacokinetics of a single dose of i.v. posaconazole in critically ill patients. Patients with no history of allergy to triazole antifungals and requiring systemic antifungal therapy were enrolled if they were aged ≥18 years, central venous access was available, they were not pregnant, and they had not received prior posaconazole or drugs interacting with posaconazole. A single dose of 300 mg posaconazole was administered over 90 min. Total plasma concentrations were measured from serial plasma samples collected over 48 h, using a validated chromatographic method. The pharmacokinetic data set was analyzed by noncompartmental methods. Eight patients (7 male) were enrolled with the following characteristics: median age, 46 years (interquartile range [IQR], 40 to 51 years); median weight, 68 kg (IQR, 65 to 82 kg); and median albumin concentration, 20 g/liter (IQR, 18 to 24 g/liter). Median (IQR) pharmacokinetic parameter estimates were as follows: observed maximum concentration during sampling period (C_max), 1,702 ng/ml (1,352 to 2,141 ng/ml); area under the concentration-time curve from zero to infinity (AUC_0-∞), 17,932 ng · h/ml (13,823 to 27,905 ng · h/ml); clearance (CL), 16.8 liters/h (11.1 to 21.7 liters/h); and volume of distribution (V), 529.1 liters (352.2 to 720.6 liters). The V and CL were greater than 2-fold and the AUC_0-∞ was 39% of the values reported for heathy volunteers. The AUC_0-∞ was only 52% of the steady-state AUC_0-24 reported for hematology patients. The median of estimated average steady-state concentrations was 747 ng/ml (IQR, 576 to 1,163 ng/ml), which is within but close to the lower end of the previously recommended therapeutic range of 500 to 2,500 ng/ml. In conclusion, we observed different pharmacokinetics of i.v. posaconazole in this cohort of critically ill patients compared to those in healthy volunteers and hematology patients.

Drug disposition before and after gastric bypass: fenofibrate and posaconazole

AIMS

Roux-en-Y gastric bypass (RYGB) alters the anatomical structure of the gastrointestinal tract, which can result in alterations in drug disposition. The aim of the present study was to evaluate the oral disposition of two compounds belonging to the Biopharmaceutical Classification System Class II - fenofibrate (bile salt-dependent solubility) and posaconazole (gastric pH-dependent dissolution) - before and after RYGB in the same individuals.

METHODS

A single-dose pharmacokinetic study with two model compounds - namely, 67 mg fenofibrate (Lipanthyl®) and 400 mg posaconazole (Noxafil®) - was performed in 12 volunteers pre- and post-RYGB. After oral administration, blood samples were collected at different time points up to 48 h after administration. Plasma concentrations were determined by high-performance liquid chromatography in order to calculate the area under the concentration-time curve up to 48 h (AUC_0-48 h ), the peak plasma concentration (C_max) and the time to reach peak concentration (T_max ).

RESULTS

After administration of fenofibrate, no relevant differences in AUC_0-48 h , C_max and T_max between the pre- and postoperative setting were observed. The geometric mean of the ratio of AUC_0-48 h post/pre-RYGB for fenofibrate was 1.10 [95% confidence interval (CI) 0.87, 1.40; P = 0.40]. For posaconazole, an important decrease in AUC_0-48 h and C_max following RYGB was shown; the geometric mean of the AUC_0-48 h post/pre-RYGB ratio was 0.68 (95% CI 0.48, 0.96; P = 0.03) and the geometric mean of the C_max pre/post-RYGB ratio was 0.60 (95% CI 0.39, 0.94; P = 0.03). The decreased exposure of posaconazole could be explained by the increased gastric pH and accelerated gastric emptying of fluids post-RYGB. No difference for T_max was observed.

CONCLUSIONS

The disposition of fenofibrate was not altered after RYGB, whereas the oral disposition of posaconazole was significantly decreased following RYGB.