Pharmacokinetic and Pharmacodynamic Alterations in the Roux-en-Y Gastric Bypass Recipients

Medication and supplement pharmacokinetic changes following bariatric surgery: A systematic review and meta-analysis

OBJECTIVES

To evaluate the impact of bariatric surgery on the pharmacokinetic (PK) parameters of orally administered medications and supplements.

METHODS

Systematic searches of bibliographic databases were conducted to identify studies. Pooled effect estimates from different surgical procedures were calculated using a random-effects model.

RESULTS

Quantitative data were synthesized from 58 studies including a total of 1985 participants. Whilst 40 medications and 6 supplements were evaluated across these studies, heterogeneity and missing information reduced the scope of the meta-analysis to the following medications and supplements: atorvastatin, paracetamol, omeprazole, midazolam, vitamin D, calcium, zinc, and iron supplements. There were no significant differences in PK parameters post-surgery for the drugs atorvastatin and omeprazole, and supplements calcium, ferritin, and zinc supplements. Paracetamol showed reduced clearance (mean difference [MD] = -15.56 L/hr, p = 0.0002, I2 = 67%), increased maximal concentration (MD = 6.90 μg/ml, p = 0.006, I2 = 92%) and increased terminal elimination half-life (MD = 0.49 hr, p < 0.0001, I2 = 3%) post-surgery. The remaining 36 medications and 2 supplements were included in a systematic review. Overall, 18 of the 53 drugs and supplements showed post-operative changes in PK parameters.

CONCLUSION

This study demonstrates heterogeneity in practice and could not reach conclusive findings for most PK parameters. Prospective studies are needed to inform best practice and enhance patient healthcare and safety following bariatric surgery.

Bioavailability of Orally Administered Drugs After Bariatric Surgery

PURPOSE OF REVIEW

Oral drug absorption after bariatric surgery is likely to be altered, but the impact of different bariatric surgery procedures on individual drugs is not uniform. The aim of this article is to describe factors influencing the bioavailability of orally administered drugs after bariatric surgery and to provide readers with practical recommendations for drug dosing. We also discuss the medications that may be harmful after bariatric surgery.

RECENT FINDINGS

The fundamental factors for enteral drug absorption are the production of gastric acid; the preserved length of the intestine, i.e., the size of the absorption surface and/or the preserved enterohepatic circulation; and the length of common loop where food and drugs are mixed with digestive enzymes and bile acids. Bypassing of metabolizing enzymes or efflux pumps and changes in intestinal motility can also play an important role. Significant changes of drug absorption early after the anatomic alteration may also be gradually ameliorated due to gradual intestinal adaptation. The most affected drugs are those with low or variable bioavailability and those undergoing enterohepatic circulation. Attention should also be paid to oral drug formulations, especially in the early postoperative period, when immediate-release and liquid formulations are preferred. The changes in oral bioavailability are especially clinically meaningful in patients treated with drugs possessing narrow therapeutic index (e.g., oral anticoagulants, levothyroxine, and anticonvulsants) or in acute conditions (e.g., anti-infectives); nevertheless, it may also influence the therapeutic value of chronic therapy (e.g., antidepressants. antihypertensives, antiplatelets, statins, PPIs, contraceptives, and analgesics); therapeutic effect of chronic therapy is further influenced by pharmacokinetic alterations resulting from weight loss. Therapeutic drug monitoring, periodical clinical evaluation, and adequate dose adjustments are necessary. Due to safety reasons, patients should avoid oral bisphosphonates, regular use of non-steroidal anti-inflammatory drugs, and, if possible, corticosteroids after bariatric surgery.

[Bariatric surgery and drugs: Review of the literature and Adverse Drug Reactions analysis in French National Pharmacovigilance Database]

INTRODUCTION

Bariatric surgery is the only treatment for severe obesity (BMI>35kg/m2) currently recognized as effective both in achieving tangible and lasting weight loss, and in improving obesity-related comorbidities such as type 2 diabetes, hypertension, and cardiovascular complications. Bariatric surgery, like any other surgery of the digestive tract, can have an impact on nutrient absorption, as well as on drug absorption. The literature on drug management in bariatric surgery patients concerned mainly of case reports and retrospective studies involving a small number of patients. No official guidelines are available.

METHODS

We conducted a literature search on the consequences of bariatric surgery in terms of drug bioavailability and/or effect. The Medline® (PubMed) database was searched using the following keywords: "bariatric surgery", "bioavailability", "gastric bypass", and "obesity". We completed this review with an analysis of reports of adverse drug reactions (ADRs) in post-bariatric surgery patients for obesity registered in the National pharmacovigilance database (PVDB). We selected all cases with the mention of "bariatric surgery and/or gastrectomy" as "medical history". After reading the cases, we excluded those in which the patient had undergone surgery for an indication other than obesity, where the route of administration was other than oral, and cases in which ADRs resulted from voluntary overdose, attempted suicide, allergy, switch to Levothyrox® new formulation, meningioma under progestative drugs, inefficacy related to generic substitution and medication error.

RESULTS

The literature search identified mainly "case report" about the impact of bariatric surgery on so-called "narrow therapeutic window" drugs. We identified 66 informative cases out of a total of 565 cases selected (11%) in the PVDB. Nevertheless, the information does not allow a clear relationship between the occurrence of the ADR and the influence of bariatric surgery.

CONCLUSION

There is a lack of official information and/or recommendations on medication use in subjects who have undergone bariatric surgery. Apart from under-reporting, ADRs reports remain largely uninformative. Health professional and patients would be awareness for improving, quantitatively and qualitatively the reporting of ADRs in this population.

The Effects of Bariatric Surgery on Pharmacokinetics of Drugs: a Review of Current Evidence

PURPOSE OF REVIEW

Obesity constitutes a major public health concern and has been recognized as an epidemic. To date, bariatric surgery remains the most effective way for substantial long-lasting weight loss in severe obesity. The purpose of this review is to summarize how the pharmacokinetics of drugs are affected by the most common types of bariatric surgery, i.e., Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG).

RECENT FINDINGS

Limited data are available regarding the changes in pharmacokinetics of drugs after bariatric surgery. The lack of existing guidelines may lead patients to experience drug toxicity or therapeutic undertreatment. Pharmacokinetic parameters that need to be taken into consideration postoperatively include gastric motility, gastric volume, pH, surface area, bile secretions, carrier proteins, and first-pass metabolism. For drugs with a narrow therapeutic index, other factors need to be monitored closely, including plasma drug levels, patients' clinical outcomes, and laboratory markers. Patients should be followed up frequently and treated in accordance with their response to the drug therapy. Bariatric surgery may affect the pharmacokinetics of various drugs, due to the resultant anatomical changes and the substantial weight loss. Therefore, there is a need to identify those potential changes and adjust patients' medication doses in order to achieve higher efficacy and avoid toxicity.

Impact of Bariatric Surgery in the Short and Long Term: A Need for Time-Dependent Dosing of Drugs

Sparse information is available on pharmacokinetic changes of drugs over time after bariatric surgery. By reviewing the literature on the short- and long-term pharmacokinetic changes of drugs, several patterns were identified for 39 drugs. No relevant pharmacokinetic changes were identified for roughly a third of the drugs. Of the remaining drugs, levels were variable and partly unpredictable shortly after the surgery. In the long term, most of the drug levels remain altered, but in some cases they returned to preoperative values. Based on the changes and the efficacy-safety balance of each drug, clinicians may need to perform additional clinical monitoring for specific drugs, including measuring drug levels. This review provides suggestions for clinicians and pharmacists for specific time-dependent drug dosing advice.

Impact of Obesity and Bariatric Surgery on Metabolic Enzymes and P-Glycoprotein Activity Using the Geneva Cocktail Approach

The inter-individual variability of CYP450s enzyme activity may be reduced by comparing the effects of bariatric surgery on CYP-mediated drug elimination in comparable patients before and after surgery. The current research will use a low-dose phenotyping cocktail to simultaneously evaluate the activities of six CYP isoforms and P-gp. The results showed that following weight reduction after surgery, the activity of all enzymes increased compared to the obese period, which was statistically significant in the case of CYP3A, CYP2B6, CYP2C9, and CYP1A2. Furthermore, the activity of P-gp after surgery decreased without reaching a statistical significance (p-value > 0.05). Obese individuals had decreased CYP3A and CYP2D6 activity compared with the control group, although only CYP3A was statistically important. In addition, there was a trend toward increased activity for CYP1A2, CYP2B6, CYP2C9, and CYP2C19 in obese patients compared to the control group, without reaching statistical insignificance (p-value ≥ 0.05). After six months (at least), all enzymes and the P-gp pump activity were significantly higher than the control group except for CYP2D6. Ultimately, a greater comprehension of phenoconversion can aid in altering the patient's treatment. Further studies are required to confirm the changes in the metabolic ratios of probes after bariatric surgery to demonstrate the findings' clinical application. As a result, the effects of inflammation-induced phenoconversion on medication metabolism may differ greatly across persons and drug CYP pathways. It is essential to apply these results to the clinic to recommend dose adjustments.

Drug absorption in bariatric surgery patients: A narrative review

Background

Despite the increase in the number of bariatric surgeries performed, little is known about the impact of the surgery on drug absorption. Unpredictability is assumed with drugs, given the anatomical changes after surgery.

Objective

To evaluate the impact of bariatric surgery on drug absorption based on the type of procedure performed.

Methods

We conducted a comprehensive literature review searching PubMed/Medline for published studies (from inception to December 2017) that evaluate the use of drugs and the assessment of drug absorption after bariatric surgery. Pharmacokinetic/pharmacodynamic studies, case reports, and observational studies were included in our review.

Results

We found 60 studies addressing drug use after bariatric surgery. Twenty‐eight studies reported a decrease in drug absorption after bariatric surgery while only four studies showed an increase in drug absorption. Unchanged absorption of drugs was seen in 23 studies after the surgery.

Conclusion

The available information shows variations in drug absorption after bariatric surgery. The unpredictability may result from factors related to the patient, drug, and/or type of surgery. Therefore, pharmacists' involvement and close monitoring of patients after bariatric surgery could be effective to avoid sub‐/supratherapeutic responses.

Short- and long-term effects of body weight, calorie restriction, and gastric bypass on CYP1A2-, CYP2C19-, and CYP2C9 activity

Aim

Roux‐en‐Y gastric bypass (RYGB) may influence drug disposition due to surgery‐induced gastrointestinal alterations and/or subsequent weight loss. The objective was to compare short‐ and long‐term effects of RYGB and diet on the metabolic ratios of paraxanthine/caffeine (cytochrome P450 [CYP] 1A2 activity), 5‐hydroxyomeprazole/omeprazole (CYP2C19 activity) and losartan/losartan carboxylic acid (CYP2C9 activity), and cross‐sectionally compare these CYP‐activities with normal‐to‐overweight controls.

Methods

This trial included patients with severe obesity preparing for RYGB (n = 40) or diet‐induced (n = 41) weight loss, and controls (n = 18). Both weight loss groups underwent a 3‐week low‐energy diet (<1200 kcal/day, weeks 0‐3) followed by a 6‐week very‐low‐energy diet or RYGB (both <800 kcal/day, weeks 3‐9). Follow‐up time was 2 years, with four pharmacokinetic investigations.

Results

Mean ± SD weight loss from baseline was similar in the RYGB‐group (13 ± 2.4%) and the diet group (10.5 ± 3.9%) at week 9, but differed at year 2 (RYGB −30 ± 6.9%, diet −3.1 ± 6.3%). From weeks 0 to 3, mean (95% confidence interval [CI]) CYP2C19 activity similarly increased in both groups (RYGB 43% [16, 55], diet 48% [22, 60]). Mean CYP2C19 activity increased by 30% (2.6, 43) after RYGB (weeks 3‐9), but not in the diet‐group (between‐group difference −0.30 [−0.63, 0.03]). CYP2C19 activity remained elevated in the RYGB group at year 2. Baseline CYP2C19 activity was 2.7‐fold higher in controls compared with patients with obesity, whereas no difference was observed in CYP1A2 and CYP2C9 activities.

Conclusion

Our findings suggest that CYP2C19 activity is lower in patients with obesity and increases following weight loss. This may be clinically relevant for drug dosing. No clinically significant effect on CYP1A2 and CYP2C9 activities was observed.

Considerations for clinical evaluation of the effects of bariatric surgery on the pharmacokinetics of orally administered drugs

Obesity has been a growing worldwide concern, and surgical intervention including bariatric surgery is considered as one of the options for treatment. However, there still is controversy over the change in pharmacokinetics (PKs) of drugs after the surgery. To investigate the potential covariates that can influence the area under the curve (AUC) and maximum plasma concentration (C_max), the design of previous studies was reviewed based on pre-determined eligibility criteria. Each study calculated the ratios of the AUC and C_max before and after bariatric surgery. These studies investigated whether the PK parameters were affected by the time after the surgery or by the type of control group. The ratio of the AUC calculated in the early and late follow-up period was similar across Roux-en Y gastric bypass patients. No significant difference in the PK parameters was found between the pre-surgical patients and matched healthy subjects. However, certain control groups could be preferable depending on the purpose of the clinical trial. Although C_max was inconsistent compared to the AUC, insufficient sampling of the time points may have caused such an inconsistency. This is the first article exploring the appropriate methodology in designing clinical studies for changes in the PK characteristics of orally administered drugs in patients with bariatric surgery.

The Effects of Bariatric Surgery and Gastrectomy on the Absorption of Drugs, Vitamins, and Mineral Elements

Bariatric surgery, which is an effective treatment for obesity, and gastrectomy, which is the primary treatment method for gastric cancer, alter the anatomy and physiology of the digestive system. Weight loss and changes in the gastrointestinal tract may affect the pharmacokinetic parameters of oral medications. Both bariatric and cancer patients use drugs chronically or temporarily. It is important to know how surgery affects their pharmacokinetics to ensure an effective and safe therapy. The Cochrane, PubMed, and Scopus databases were searched independently by two authors. The search strategy included controlled vocabulary and keywords. Studies show that bariatric surgery and gastrectomy most often reduce the time to maximum plasma concentration (t_max) and decrease the maximum plasma concentration (C_max) in comparison with the values of these parameters measured in healthy volunteers. Vitamin and mineral deficiencies are also observed. The effect depends on the type of surgery and the properties of the drug. It is recommended to use the drugs that have been tested on these groups of patients as it is possible to monitor them.

Is Gastric Bypass a Risk Factor for Complicated Alcohol Withdrawal? Case Report and Literature Review

Alcohol use disorder and gastric bypass surgery are highly comorbid. Alcohol withdrawal syndrome (AWS) is a common and potentially life-threatening event, requiring nuanced and individually tailored management depending on various clinical factors including patient history, alcohol consumption, comorbidities, and timeline of use. Although increasingly common, the literature for managing alcohol withdrawal in the gastric bypass population is quite limited. We present the case of a 45-year-old woman with a past history of Roux-en-Y gastric bypass admitted for alcohol withdrawal at a psychiatric hospital who experienced a complicated withdrawal despite adhering to standard management guidelines. She had been consuming 8 to 12 standard drinks daily, and she was therefore monitored on a Clinical Institute Withdrawal Assessment for Alcohol. She experienced only minimal withdrawal symptoms up to 48 hours following cessation of alcohol consumption. At 70 hours postcessation, she experienced a witnessed tonic-clonic seizure with associated head trauma with internal bleeding, requiring acute medical intervention. This timeline of withdrawal symptoms is atypical, yet perhaps understood in the context of her past medical history which included gastric bypass surgery. We discuss the potential complicating factors inherent in individuals who have received Roux-en-Y gastric bypass in the past with respect to alcohol metabolism. We discuss the similar considerations with respect to altered metabolism of therapeutics commonly used in managing this condition. Lastly, we include a review of the extent literature on this topic and propose possible considerations for managing this unique but increasingly prevalent clinical scenario.

Oral drug dosing following bariatric surgery: General concepts and specific dosing advice

Bariatric or weight‐loss surgery is a popular option for weight reduction. Depending on the surgical procedure, gastric changes like decreased transit time and volume and increased pH, decreased absorption surface in the small intestine, decreased exposure to bile acids and enterohepatic circulation, and decreased gastrointestinal transit time may be expected. In the years after bariatric surgery, patients will also substantially lose weight. As a result of these changes, the absorption, distribution, metabolism and/or elimination of drugs may be altered. The purpose of this article is to report the general influence of bariatric surgery on oral drug absorption, and to provide guidance for dosing of commonly used drugs in this special population. Upon oral drug administration, the time to maximum concentration is often earlier and this concentration may be higher with less consistent effects on trough concentrations and exposure. Additionally, prescription of liquid formulations to bariatric patients is supported by some reports, even though the high sugar load of these suspensions may be of concern. Studies on extended‐release medications result in an unaltered exposure for a substantial number of drugs. Also, studies evaluating the influence of timing after surgery show dynamic absorption profiles. Although for this group specific advice can be proposed for many drugs, we conclude that there is insufficient evidence for general advice for oral drug therapy after bariatric surgery, implying that a risk assessment on a case‐by‐case basis is required for each drug.

Impact of gastrointestinal tract variability on oral drug absorption and pharmacokinetics: An UNGAP review

The absorption of oral drugs is frequently plagued by significant variability with potentially serious therapeutic consequences. The source of variability can be traced back to interindividual variability in physiology, differences in special populations (age- and disease-dependent), drug and formulation properties, or food-drug interactions. Clinical evidence for the impact of some of these factors on drug pharmacokinetic variability is mounting: e.g. gastric pH and emptying time, small intestinal fluid properties, differences in pediatrics and the elderly, and surgical changes in gastrointestinal anatomy. However, the link of colonic factors variability (transit time, fluid composition, microbiome), sex differences (male vs. female) and gut-related diseases (chronic constipation, anorexia and cachexia) to drug absorption variability has not been firmly established yet. At the same time, a way to decrease oral drug pharmacokinetic variability is provided by the pharmaceutical industry: clinical evidence suggests that formulation approaches employed during drug development can decrease the variability in oral exposure. This review outlines the main drivers of oral drug exposure variability and potential approaches to overcome them, while highlighting existing knowledge gaps and guiding future studies in this area.

Adaptations in gastrointestinal physiology after sleeve gastrectomy and Roux-en-Y gastric bypass

Linked to the growing obesity epidemic, demand for bariatric and metabolic surgery has increased, the most common procedures being sleeve gastrectomy and Roux-en-Y gastric bypass. Originally, bariatric procedures were described as purely restrictive, malabsorptive, or combined restrictive-malabsorptive procedures limiting food intake, nutrient absorption, or both. Nowadays, anatomical alterations are known to affect gastrointestinal physiology, which in turn affects the digestion and absorption of nutrients and drugs. Therefore, understanding gastrointestinal physiology is crucial to prevent postoperative nutritional deficiencies and to optimise postoperative drug therapy. Preclinical and clinical research indicates that sleeve gastrectomy accelerates liquid and solid gastric emptying and small intestinal transit, and increases bile acid serum levels, whereas its effects on gastrointestinal acidity, gastric and pancreatic secretions, surface area, and colonic transit remain largely unknown. Roux-en-Y gastric bypass diminishes gastric acid secretion, accelerates liquid gastric emptying, and increases bile acid serum levels, but its effects on intestinal pH, solid gastric emptying, intestinal transit time, gastric enzyme secretions, and surface area remain largely unknown. In this Review, we summarise current knowledge of the effects of these two procedures on gastrointestinal physiology and assess the knowledge gaps.

Enteral Medication for the Tube-Fed Patient: Making This Route Safe and Effective

The administration of medication through an enteral access device requires important forethought. Meeting a patient's therapeutic needs requires achieving expected drug bioavailability without increasing the risk for toxicity, therapeutic failure, or feeding tube occlusion. Superimposing gut dysfunction, critical illness, or enteral nutrition-drug interaction further increases the need for a systematic approach to prescribing, evaluating, and preparing a drug for administration through an enteral access device. This review will explain the fundamental factors involved in drug bioavailability through the gut, address the influencing considerations for the enterally fed patient, and describe best practices for enteral drug preparation and administration.

Hydroxyurea Pharmacokinetics in Pediatric Patients After Total Pancreatectomy With Islet Autotransplantation

Total pancreatectomy with islet autotransplantation is a complex surgical approach for acute recurrent or chronic pancreatitis that frequently triggers extreme thrombocytosis (platelets ≥ 1000 × 10⁹ /L). Thrombocytosis can be prothrombotic, so cytoreductive hydroxyurea is often initiated after this surgery; however, optimal dosing strategy and efficacy are unknown. This prospective pilot study characterized the pharmacokinetics of hydroxyurea after this procedure in children. It also compared them with previously published pediatric parameters in sickle cell anemia (SCA), the disease in which pediatric hydroxyurea pharmacokinetics have primarily been studied. Plasma hydroxyurea levels were quantified in 14 participants aged 4-19 years using high-performance liquid chromatography. Blood collections were scheduled 20 minutes, 1 hour, and 4 hours after the first dose, on pharmacokinetic day 1 (PK1), and again 2-3 months later if still on hydroxyurea (PK2). Six participants had PK1 and PK2 data at all 3 postdose timed collections, 5 only had PK1 samples, and 3 only had PK2 samples. Total pancreatectomy with islet autotransplantation participants had reduced and delayed absorption compared with sickle cell anemia participant data from the Hydroxyurea Study of Long-Term Effects, regardless of timing or dosing methodology. Total pancreatectomy with islet autotransplantation participants had different pharmacokinetic profiles at PK1 versus PK2, with lower dose-normalized exposures than previously reported in sickle cell anemia. These results suggest variability exists in hydroxyurea absorption and bioavailability in total pancreatectomy with islet autotransplantation patients, suspected to be primarily because of Roux-en-Y reconstruction, and suggest that more pharmacokinetic data are needed for scenarios when hydroxyurea is prescribed to children without sickle cell anemia.

Impact of bariatric surgery on oral anticoagulants pharmacology, and consequences for clinical practice: a narrative review

The prevalence of obesity has been steadily increasing in recent years worldwide. At the same time bariatric surgery, the best therapeutic strategy to date in terms of sustainable weight loss and improvement of associated comorbidities has been also increasing. However, these surgeries, whether primarily restrictive or malabsorptive, raise questions about the pharmacology of oral drugs. Among widely used drugs, anticoagulants are the referent therapy to treat some cardiovascular diseases such as atrial fibrillation and venous thromboembolism. How bariatric surgery may impact pharmacological properties of oral anticoagulants, and more specifically, direct oral anticoagulants (DOACs) are difficult to anticipate. In this review, we describe available data concerning the potential impact of bariatric surgery on the pharmacology of oral anticoagulants. The vitamin K antagonists (VKAs) requirements for the same international normalized ratio target are reduced after bariatric surgery. Limited data available for dabigatran 150 mg twice daily indicate a risk of insufficient efficacy in atrial fibrillation after gastric bypass due to probable impaired absorption. Data for rivaroxaban at the prophylactic dose of 10 mg per day suggest no impact of bariatric surgery from 3 days to 8 months post-surgery. However, no conclusive data are available for other anticoagulants or the use of DOACs at therapeutic doses. To date, DOACs are not recommended in patients who have undergone bariatric surgery, because of limited available data. Pending new studies to confirm the predictable pharmacokinetics and safety of DOACs in this population, especially at therapeutic doses, VKAs remain the first option for chronic anticoagulation.

Pharmacokinetics of Oral Levonorgestrel in Women After Roux-en-Y Gastric Bypass Surgery and in BMI-Matched Controls

BACKGROUND

Women are advised to primarily use non-oral contraceptive alternatives after Roux-en-Y gastric bypass since it is not known if the surgery affects the pharmacokinetics of oral contraceptives.

METHODS

This is a multi-center, open label, phase 2 pharmacokinetic study performed at the University Hospital of Linköping and the Clinical Trials Center, Department of Obstetrics and Gynecology, Danderyd Hospital, Karolinska Institutet, Stockholm, Sweden. Fifteen women aged 18-40 years who had previously undergone Roux-en-Y gastric bypass surgery and reached a BMI < 30 were included. Fifteen BMI-matched women with no previous history of Roux-en-Y gastric bypass surgery served as a control group. After administration of a single dose of a combined oral contraceptive containing 0.03 mg ethinylestradiol/0.15 mg levonorgestrel, serum levonorgestrel concentrations were determined during a 24-h period using ultra performance liquid chromatography/tandem mass spectrometry. The area under the plasma concentration time curve of levonorgestrel (AUC0-24h) was the main outcome measure.

RESULTS

There were no significant differences in the studied pharmacokinetic parameters, AUC0-24h, total AUC, peak serum concentration (Cmax), time to peak serum concentrations (Tmax), apparent oral clearances of levonorgestrel (CLoral), or terminal half-lives (t½) between the groups.

CONCLUSION

This is to our knowledge the first study to evaluate the pharmacokinetics of oral levonorgestrel in women with a BMI < 30 at least 1 year after RYGB compared with a BMI-matched group of women. We could not find any significant pharmacokinetic differences between the groups, suggesting that oral levonorgestrel may be used in non-obese women after Roux-en-Y gastric bypass once a stable body weight has been reached.

CLINICAL TRIAL NUMBER

EudraCT 2014-004677-17.

Nanotechnology as a tool to overcome the bariatric surgery malabsorption

Obesity is a metabolic disease that affects all ages; it is considered life-threatening condition as it leads to fatal complications such as; cardiovascular diseases and diabetes. The therapeutic options include; life-style modifications, pharmacotherapy intervention, and surgical intervention. Bariatric surgery (BS) is considered as the most effective option among the others for its rapid weight loss, maintaining the lost mass, and improving the quality of life of the patients. Nevertheless, BS leads to severe changes in the bioavailability of medications, especially for chronic diseases, which may reach to limit where the patient's life endangers. Recently, pharmaceutical formulations had developed several methods to improve the drug bioavailability of drugs though the implying of nanotechnology. Nonotechnology is responsible for reducing the size of the drugs to the nano range (<1000 nm), which increase the drug surface area, dissolution, absorption, and, most importantly, the bioavailability of these drugs. It is believed that BS malabsorption and drugs bioavailability problems can be solved using nanotechnology for its advantages in overcoming BS complications.

Modern pharmacological treatment of obese patients

There are many angles to consider in drug treatment of obese patients. On the one hand, some specific weight loss drugs are available, on the other, several drugs are associated with unintentional weight changes. When treating an obese patient for any given disease, several physiological changes may influence the pharmacokinetic properties of the drugs required. Thus, increased body weight may influence the efficacy and safety of some drug treatments. Even more complicated is the situation after weight reduction surgery. Due to the various changes to the gastrointestinal tract induced by the different surgical techniques used, and the dynamic changes in body composition thereafter, drug dosing has to be constantly reconsidered. Whereas all of these issues are of clinical importance, none of them have been investigated in the necessary depth and broadness to ensure safe and efficacious drug treatment of the massively obese patient. Individual considerations have to be based on comorbidities, concomitant medication, and on specific drug properties, for example, lipophilicity, volume of distribution, and metabolism. In this article we summarize the data available on different aspects of drug treatment in the obese patient with the hope of improving patient care.

Short- and medium-term impact of bariatric surgery on the activities of CYP2D6, CYP3A4, CYP2C9, and CYP1A2 in morbid obesity

Morbid obesity and bariatric surgery induce anatomical, physiological and metabolic alterations that may alter the body’s disposition of drugs. Current literature on this topic is limited and sometimes inconsistent. Cytochrome P450 (CYP) is a superfamily of enzymes that metabolize around 75% of all marketed drugs. The purpose of this study was to evaluate the impact of body mass index and bariatric surgery on CYP activities. Firstly, we evaluated the in vivo activity of 4 major CYP isoenzymes (CYP2D6, CYP3A4, CYP2C9, and CYP1A2) in normal weight, overweight, and morbidly obese individuals. Secondly, we assessed the short- (1 month) and medium-term (6 month) effects of the most commonly employed bariatric surgery techniques (laparoscopic sleeve gastrectomy and Roux-en-Y gastric bypass) on the activity of these enzymes. CYP3A4 activity was lower in morbidly obese individuals, compared to normal-weight controls. Interestingly, bariatric surgery normalized CYP3A4 activity. In comparison with normal-weight controls, morbidly obese individuals had higher CYP2D6 activity, which was only observed in individuals with two functional alleles for this isoenzyme. Neither body mass index nor surgery had significant effects on CYP2C9 and CYP1A2 activities. Overall, no relevant differences in CYP activities were found between surgical techniques. In conclusion, further studies should evaluate whether the observed alterations in CYP3A4 activity will require dose adjustments for CYP3A4 substrates especially in morbidly obese individuals before and after bariatric surgery.

Efficacy of Low Dose Proton Pump Inhibitor-Based Therapy to Eradicate Helicobacter pylori in Patients with Subtotal Gastrectomy

Proton pump inhibitor (PPI)-based therapy is standard to eradicate Helicobacter pylori (H. pylori). Gastric acidity is lowered after gastrectomy because of bile reflux and impaired mechanism of acid secretion. Therefore, low-dose PPI may be effective for H. pylori eradication in the remnant stomach after gastrectomy. In this study, we compared the efficacy of low-dose PPI with standard double-dose PPI to eradicate H. pylori in patients who underwent subtotal gastrectomy. A total of 145 patients who were treated for eradication after gastrectomy was analyzed. They were treated with PPI-based triple regimen (PPI, clarithromycin and amoxicillin) for 14 days. We compared the eradication rate in the low-dose PPI group (lansoprazole 15 mg once daily) with that in the standard double-dose PPI group (lansoprazole 30 mg twice daily). The H. pylori eradication rate was 79.1% in the low-dose PPI group and 85.3% in the standard double-dose group; the difference was not significant statistically (p = 0.357). In the multivariate analysis, low-dose PPI (odds ratio (OR) = 1.79, 95% confidence interval (CI), 0.68–4.69) was not associated with eradication failure, while Billroth II anastomosis (OR = 4.45, 85% CI, 1.23–16.2) was significantly associated with eradication failure. Low-dose PPI-based triple regimen was as effective as standard double-dose PPI-based regimen for H. pylori eradication in patients with subtotal gastrectomy. Further study is needed to confirm the effect of low-dose PPI on H. pylori eradication in patients with gastrectomy.

Laparoscopic Roux-en-Y gastric bypass surgery influenced pharmacokinetics of several drugs given as a cocktail with the highest impact observed for CYP1A2, CYP2C8 and CYP2E1 substrates

There is a lack of information about the changes in drug pharmacokinetics and cytochrome P450 (CYP) metabolism after bariatric surgery. Here, we investigated the effects of laparoscopic Roux-en-Y gastric bypass (LRYGB) surgery on pharmacokinetics of nine drugs given simultaneously which may reveal changes in the activities of the main CYPs. Eight obese subjects undergoing LRYGB received an oral cocktail containing nine drugs, substrates of various CYPs: melatonin (CYP1A2), nicotine (CYP2A6), bupropion (CYP2B6), repaglinide (CYP2C8), losartan (CYP2C9), omeprazole (CYP2C19/CYP3A4), dextromethorphan (CYP2D6), chlorzoxazone (CYP2E1) and midazolam (CYP3A). The 6-hours pharmacokinetic profiles in serum and urine of each drug or corresponding metabolite as well as their metabolic ratios were compared before surgery with those at a median 1 year later. LRYGB exerted variable effects on the pharmacokinetics of these drugs. The geometric mean AUC_0-6 (90% confidence interval) of melatonin, bupropion, repaglinide, chlorzoxazone and midazolam after LRYGB was 27 (19%-41%), 54 (43%-67%), 44 (29%-66%), 160 (129%-197%) and 74 (62%-90%) of the pre-surgery values, respectively. The pharmacokinetics of losartan, omeprazole and dextromethorphan did not change in response to surgery. Nicotine was not detected in serum, while geometric mean of AUC_0-6 of its metabolite, cotinine, increased by 1.7 times after surgery. There were 3.6- and 1.3-fold increases in the AUC ratios of 6-hydroxymelatonin/melatonin and hydroxybupropion/bupropion, respectively. The cocktail revealed multiple pharmacokinetic changes occurring after LRYGB with the greatest effects observed for CYP1A2, CYP2C8 and CYP2E1 substrates. Future studies should be focused on CYP1A2, CYP2A6, CYP2C8 and CYP2B6 to clarify the changes in activities of these enzymes after LRYGB.

Glucocorticoids dosing in obese subjects: A systematic review

Glucocorticoids (GCs) are amongst the most widely used and effective treatments to control inflammatory and autoimmune diseases. In obese subjects, drug dosing adjusted by body weight is problematic, all the more so as patients are at higher risk of GC metabolic side effects. We propose here to describe the determinants of drug pharmacokinetics (PK) in obese subjects and GC pharmacology, and to identify the existing PK studies that may help discussing the best size descriptor for GC dosing in obese subjects. A clinician and a pharmacist screened PubMed using the MeSH Terms: "glucocorticoids" OR "steroidal agents" AND "pharmacokinetics" AND "obesity" OR "overweight". The search was limited to the publications written in English language and to those performed in humans. A systematic search using the MeSH terms was performed until August 31st, 2017. Only three such PK studies have been published so far that compare dexamethasone, prednisolone and methylprednisolone in obese and normal weight subjects. The studies concur that GC partially distribute in the excess of body weight and that adjustment by total body weight (TBW) or by body weight (BW) excess would increase the initial plasma GC concentration after a loading dose and would thus be inappropriate. Contradictory results are observed regarding GC exposure or clearance according to the GC studied. Behind this overwhelming lack of conclusive evidence for adjusting GC by body weight, further PK studies are clearly needed for guiding their dosing. Furthermore, studies demonstrated an increased sensibility to GC, even when GC exposure was reduced, suggesting that adjustment by body weight may not only be unnecessary but also dangerous.

Plasma concentrations of etonogestrel in women using oral desogestrel before and after Roux-en-Y gastric bypass surgery: a pharmacokinetic study

OBJECTIVE

To investigate whether Roux-en-Y gastric bypass (RYGB) affects oral desogestrel (etonogestrel) pharmacokinetics.

DESIGN

Single centre, open label, phase-2 pharmacokinetic study.

SETTING

University hospital of Linköping, Sweden.

POPULATION

Fourteen women with planned RYGB surgery were included; nine women aged 18-45 years using 75 micrograms desogestrel completed the study.

METHODS

Steady-state etonogestrel pharmacokinetic (PK) parameters were measured on three occasions for each individual (at 8 ± 6 weeks before surgery, and at 12 ± 2 and 52 ± 2 weeks after surgery). Each patient served as her own control. On each occasion, serum samples were collected during a 24-hour period and etonogestrel concentrations were determined with ultra-performance liquid chromatography/tandem mass spectrometry.

MAIN OUTCOME MEASURES

Area under the plasma concentration time curve of etonogestrel (AUC_{0-24 hours} ).

RESULTS

All women had significant postoperative weight loss. There were no significant differences in AUC_{0-24 hours} , terminal half-lives (t_½ ), time to peak serum concentrations (T_max ), or apparent oral clearances of etonogestrel (CL_oral ) before and after gastric bypass surgery on any occasion. Peak serum concentrations (C_max ) increased after 52 ± 2 weeks compared with preoperative values (0.817 ng/ml versus 0.590 ng/ml, P = 0.024).

CONCLUSION

To our knowledge, this is the first study to investigate the effects on desogestrel pharmacokinetics after RYGB. This study did not reveal any clinically significant changes in etonogestrel pharmacokinetics, suggesting that oral desogestrel may be used by women after RYGB surgery. The sample size was limited, however, and therefore the results should be interpreted cautiously.

TWEETABLE ABSTRACT

The pharmacokinetics of oral desogestrel does not appear to change after gastric bypass surgery.

Diabetes management before, during, and after bariatric and metabolic surgery

Metabolic surgery is unrivaled by other therapeutic modalities due to its ability to foster diabetes remission. Metabolic surgery is an integral therapeutic modality in obese and morbidly obese populations because pharmacological and behavioral therapy often fail to effectively manage type II diabetes. However, given the invasiveness of the metabolic surgery relative to behavioral therapy and the need to conform to preparatory and discharge guidelines, patients must adhere to strict nutritional and diabetes management protocols. Also, the pharmacological regimen that is instituted upon discharge is distinct from the preoperative regimen. Oftentimes, the dose for insulin and oral medications are significantly decreased or withdrawn. As time elapses and depending on several factors (e.g., exercise adherence), diabetes control becomes tenuous in a small portion of the patients because there is weight regain and on-going beta cell failure. At this time interval, intensification of diabetes therapy becomes prudent. Indeed, pharmacotherapy from the preoperative to the postoperative phase is labile and may be complex. Therefore, by discussing pharmacology options during the preoperative, perioperative, and postoperative period, the goal is to guide clinician-driven care.

Impact of body weight, low energy diet and gastric bypass on drug bioavailability, cardiovascular risk factors and metabolic biomarkers: protocol for an open, non-randomised, three-armed single centre study (COCKTAIL)

INTRODUCTION

Roux-en-Y gastric bypass (GBP) is associated with changes in cardiometabolic risk factors and bioavailability of drugs, but whether these changes are induced by calorie restriction, the weight loss or surgery per se, remains uncertain. The COCKTAIL study was designed to disentangle the short-term (6 weeks) metabolic and pharmacokinetic effects of GBP and a very low energy diet (VLED) by inducing a similar weight loss in the two groups.

METHODS AND ANALYSIS

This open, non-randomised, three-armed, single-centre study is performed at a tertiary care centre in Norway. It aims to compare the short-term (6 weeks) and long-term (2 years) effects of GBP and VLED on, first, bioavailability and pharmacokinetics (24 hours) of probe drugs and biomarkers and, second, their effects on metabolism, cardiometabolic risk factors and biomarkers. The primary outcomes will be measured as changes in: (1) all six probe drugs by absolute bioavailability area under the curve (AUC_oral/AUC_iv) of midazolam (CYP3A4 probe), systemic exposure (AUC_oral) of digoxin and rosuvastatin and drug:metabolite ratios for omeprazole, losartan and caffeine, levels of endogenous CYP3A biomarkers and genotypic variation, changes in the expression and activity data of the drug-metabolising, drug transport and drug regulatory proteins in biopsies from various organs and (2) body composition, cardiometabolic risk factors and metabolic biomarkers.

ETHICS AND DISSEMINATION

The COCKTAIL protocol was reviewed and approved by the Regional Committee for Medical and Health Research Ethics (Ref: 2013/2379/REK sørøst A). The results will be disseminated to academic and health professional audiences and the public via presentations at conferences, publications in peer-reviewed journals and press releases and provided to all participants.

TRIAL REGISTRATION NUMBER

NCT02386917.

Higher Midazolam Clearance in Obese Adolescents Compared with Morbidly Obese Adults

BACKGROUND

The clearance of cytochrome P450 (CYP) 3A substrates is reported to be reduced with lower age, inflammation and obesity. As it is unknown what the overall influence is of these factors in the case of obese adolescents vs. morbidly obese adults, we studied covariates influencing the clearance of the CYP3A substrate midazolam in a combined analysis of data from obese adolescents and morbidly obese adults.

METHODS

Data from 19 obese adolescents [102.7 kg (62-149.5 kg)] and 20 morbidly obese adults [144 kg (112-186 kg)] receiving intravenous midazolam were analysed, using population pharmacokinetic modelling (NONMEM 7.2). In the covariate analysis, the influence of study group, age, total body weight (TBW), developmental weight (WTfor age and length) and excess body weight (WTexcess = TBW - WTfor age and length) was evaluated.

RESULTS

The population mean midazolam clearance was significantly higher in obese adolescents than in morbidly obese adults [0.71 (7%) vs. 0.44 (11%) L/min; p < 0.01]. Moreover, clearance in obese adolescents increased with TBW (p < 0.01), which seemed mainly explained by WTexcess, and for which a so-called 'excess weight' model scaling WTfor age and length to the power of 0.75 and a separate function for WTexcess was proposed.

DISCUSSION

We hypothesise that higher midazolam clearance in obese adolescents is explained by less obesity-induced suppression of CYP3A activity, while the increase with WTexcess is explained by increased liver blood flow. The approach characterising the influence of obesity in the paediatric population we propose here may be of value for use in future studies in obese adolescents.

Omeprazole Absorption and Fasting Gastrinemia After Roux-en-Y Gastric Bypass

PURPOSE

Roux-en-Y gastric bypass (RYGB) is one of the bariatric surgeries most frequently performed worldwide. Since this operation may predispose to the formation of peptic ulcer of the gastrojejunal anastomosis, the use of proton pump inhibitors (PPI) is recommended during the first postoperative year. However, so far, there is no detailed knowledge about the absorption of this medication during the immediate postoperative period and consequently about its effectiveness in blocking acid secretion. The objective was to assess the possible endoscopic peptic changes, the absorption of omeprazole (OME), and the status of fasting gastrinemia before and after RYGB operation.

MATERIALS AND METHODS

OME absorption, the production of its metabolites omeprazole sulfone (OMES) and 5-hydroxyomeprazole (HOME), and basal (fasting) gastrinemia were determined in patients submitted to RYGB before and 2 months after the operation. Upper digestive endoscopy (UDE) was also performed before and 6 months after the operation.

RESULTS

Twenty patients were studied. Preoperatively, all these patients had some peptic changes and 55% tested positive for Helicobacter pylori. Six months after surgery, ten patients still showed endoscopic changes and one patient tested positive for H. pylori. During the postoperative period, there was a reduction of OME absorption and of the production of its metabolites 90 min after administration of the drug, and reduction of serum gastrin levels.

CONCLUSION

The standard OME dose (40 mg) administered after bariatric surgery is insufficient to achieve serum levels that can effectively block the production of hydrochloric acid, permitting the formation of peptic injuries in many patients.

The Effect of Roux-en-Y Gastric Bypass Surgery in Morbidly Obese Patients on Pharmacokinetics of (Acetyl)Salicylic Acid and Omeprazole: the ERY-PAO Study

BACKGROUND

Data on the absorption of orally administered drugs following Roux-en-Y gastric bypass (RYGB) surgery in obese patients are limited and inconclusive. As it is difficult to predict changes in absorption, studies on frequently used drugs in this population are necessary. Acetylsalicylic acid (ASA) and omeprazole are two commonly prescribed drugs in obese patients.

METHODS

In this repeated measures study, omeprazole and salicylic acid (SA) serum concentrations were measured before and after RYGB in 34 morbidly obese subjects. Time to maximum concentration (Tmax), lag time (Tlag), maximum concentration (Cmax), and area under the serum concentration versus time curve (AUC) were calculated for both drugs to determine possible differences in drug absorption after the procedure.

RESULTS

For SA, Tmax significantly decreased after RYGB, while both Cmax and AUC0-24 significantly increased. For omeprazole, both Tmax and Tlag significantly decreased after RYGB, while Cmax significantly increased. Mean AUC0-12 significantly decreased post-surgery. The difference in AUC0-12 before and after surgery varied between subjects.

CONCLUSIONS

Our study shows a faster absorption of both ASA and omeprazole after RYGB. The exposure to ASA is higher post-surgery, but the standard dose of 80 mg does not need to be modified, considering its range in effective dose. The exposure to omeprazole is, on average, decreased after surgery. Clinicians should be aware to increase the dose of omeprazole if symptoms suggest inadequate response.

RYGB and Drug Disposition: How to Do Better? Analysis of Pharmacokinetic Studies and Recommendations for Clinical Practice

An important issue in the follow-up of patients with bariatric surgery remains to determine whether their therapeutic management should be different after surgery. In this article, we first reviewed all pharmacokinetic studies involving at least four subjects who underwent the Roux-en-Y gastric bypass (RYGB) bariatric surgery. Twenty-five publications were selected and, overall, 25 drugs were studied. Drug solubility and permeability parameters for each drug were defined using different parameters or classifications. Increased rates of oral drug absorption were predominantly observed. Conversely, drug exposure differed from one drug to another. Considering the galenic formulation and the Biopharmaceutics Classification System (BCS) class may help the prediction of oral drug exposure outcome after RYGB. We propose a strategy aiming to guide prescription and drug monitoring in patients with RYGB. But further research is clearly needed due to the unique characteristics of the bariatric population. Priority should be given to drugs that do not have clinical or biological surrogates for dose adaptation.

Oral drug therapy following bariatric surgery: an overview of fundamentals, literature and clinical recommendations

Bariatric surgery is the most effective solution for severe obesity and obesity with comorbidities, and the number of patients going through bariatric surgery is rapidly and constantly growing. The modified gastrointestinal anatomy of the patient may lead to significant pharmacokinetic alterations in the oral absorption of drugs after the surgery; however, because of insufficient available literature and inadequate awareness of the medical team, bariatric surgery patients may be discharged from the hospital with insufficient instructions regarding their medication therapy. In this article, we aim to present the various mechanisms by which bariatric surgery may influence oral drug absorption, to provide an overview of the currently available literature on the subject, and to draw guidelines for the recommendations bariatric surgery patients should be instructed before leaving the hospital. To date, and until more robust data are published, it is essential to follow and monitor patients closely for safety and efficacy of their medication therapies, both in the immediate and distant time post-surgery.

Sedation Challenges: Obesity and Sleep Apnea

This article reviews the data for diagnostic and uncomplicated therapeutic upper endoscopy, which show it is safe and effective to perform the procedure under moderate sedation with a combination of benzodiazepine and opioids. For more complex procedures or for superobese patients anesthesia support is recommended. Performing endoscopy in this population should alert providers to plan carefully and individualize sedation plans because there is no objective way to quantify this risk pre-endoscopically.

Long-term pharmacotherapy considerations in the bariatric surgery patient

PURPOSE

Pharmacists' role in optimizing long-term pharmacotherapy for bariatric surgery patients is detailed.

SUMMARY

Bariatric surgery patients provide a difficult challenge in terms of many pharmacotherapy issues, especially in the chronic care setting, where data on long-term effects of bariatric surgery are limited. The most common procedures are Roux-en-Y gastric bypass (RYGB), adjustable gastric banding, and sleeve gastrectomy. Sleeve gastrectomy has become the most common procedure in the United States, primarily because it has less overall chronic malabsorption effects than RYGB. Pharmacotherapy management is complicated by rapid weight loss combined with a number of pharmacokinetic changes, such as decreased absorption of some medications due to altered gastrointestinal tract anatomy and potentially increased concentrations of some medications due to a decreased volume of distribution resulting from weight loss. Nutritional and metabolic supplementation are of the utmost importance in order to limit deficiencies that can lead to a number of conditions. Many chronic diseases, including hypertension, diabetes, gastroesophageal reflux disease, and urinary incontinence, are improved by bariatric surgery but require close monitoring to ensure the effectiveness of maintenance pharmacotherapy and avoidance of adverse effects. Psychotropic medication management is also an important pharmacotherapy concern, as evidenced by antidepressants being the most commonly used medication class among preoperative bariatric surgery patients.

CONCLUSION

Pharmacists have an increasing role in the chronic management of the bariatric surgery patient due to their knowledge of medication dosage forms and expertise in disease states affected by bariatric surgery.

Contraceptive Use Before and After Gastric Bypass: a Questionnaire Study

Background

At present, women are recommended to avoid pregnancy 12–18 months after bariatric surgery. Our aim in this study was to describe patterns of contraceptive use before and after gastric bypass in Sweden, and to describe the contraceptive counseling given preoperatively to women undergoing gastric bypass.

Methods

In October 2012, a questionnaire was sent to 1000 Swedish women who all had undergone gastric bypass during 2010. The women had been included in the Scandinavian Obesity Surgery Register at time of surgery. The main outcome measures were patterns of use of contraception before and after bariatric surgery.

Results

The response rate was 57 %. The most commonly used contraceptive methods were intrauterine devices, 29 % preoperatively and 26 % postoperatively even though there was a postoperative switch from the copper intrauterine device to the levonorgestrel intrauterine system. Thirty percent did not use any contraceptive during the first 12 months after surgery. Sixty percent of the responders were aware of the recommendations to avoid pregnancy after surgery.

Conclusions

Many women who undergo bariatric surgery are not using any contraceptive method despite the recommendation that they should avoid pregnancy for at least 12 months. There is a great need to improve contraceptive counseling for this growing group of women.

Semiphysiologically based pharmacokinetic model for midazolam and CYP3A mediated metabolite 1-OH-midazolam in morbidly obese and weight loss surgery patients

This study aimed to describe the pharmacokinetics of midazolam and its cytochrome P450 3A (CYP3A) mediated metabolite 1‐OH‐midazolam in morbidly obese patients receiving oral and i.v. midazolam before (n = 20) and one year after weight loss surgery (n = 18), thereby providing insight into the influence of weight loss surgery on CYP3A activity in the gut wall and liver. In a semiphysiologically based pharmacokinetic (semi‐PBPK) model in which different blood flow scenarios were evaluated, intrinsic hepatic clearance of midazolam (CL_int,H) was 2 (95% CI 1.40–1.64) times higher compared to morbidly obese patients before surgery (P < 0.01). Midazolam gut wall clearance (CL_int,G) was slightly lower in patients after surgery (P > 0.05), with low values for both groups. The results of the semi‐PBPK model suggest that, in patients after weight loss surgery, CYP3A hepatic metabolizing capacity seems to recover compared to morbidly obese patients, whereas CYP3A mediated CL_int,G was low for both populations and showed large interindividual variability.

The Pharmacokinetics of the CYP3A Substrate Midazolam in Morbidly Obese Patients Before and One Year After Bariatric Surgery

PURPOSE

Bariatric surgery is nowadays commonly applied as treatment for morbid obesity (BMI > 40 kg/m(2)). As information about the effects of this procedure on a drug's pharmacokinetics is limited, we aimed to evaluate the pharmacokinetics of CYP3A probe substrate midazolam after oral and intravenous administration in a cohort of morbidly obese patients that was studied before and 1 year post bariatric surgery.

METHODS

Twenty morbidly obese patients (aged 26-58 years) undergoing bariatric surgery participated in the study of which 18 patients returned 1 year after surgery. At both occasions, patients received 7.5 mg oral and 5 mg intravenous midazolam separated by 160 ± 48 min. Per patient and occasion, a mean of 22 blood samples were collected. Midazolam concentrations were analyzed using population pharmacokinetic modeling.

RESULTS

One year after bariatric surgery, systemic clearance of midazolam was higher [0.65 (7%) versus 0.39 (11%) L/min, mean ± RSE (P < 0.01), respectively] and mean oral transit time (MTT) was faster [23 (20%) versus 51 (15%) minutes (P < 0.01)], while oral bioavailability was unchanged (0.54 (9%)). Central and peripheral volumes of distribution were overall lower (P < 0.05).

CONCLUSIONS

In this cohort study in morbidly obese patients, systemic clearance was 1.7 times higher 1 year after bariatric surgery, which may potentially result from an increase in hepatic CYP3A activity per unit of liver weight. Although MTT was found to be faster, oral bioavailability remained unchanged, which considering the increased systemic clearance implies an increase in the fraction escaping intestinal first pass metabolism.

Psychopharmacology and Bariatric Surgery

Currently, it has been demonstrated that psychotropic drugs, particularly antidepressants, are frequently prescribed for patients who seek bariatric surgery. Many bariatric surgery patients have a history of a mood disorder. Unlike medications for diabetes, hypertension or hyperlipidemia, which are generally reduced and at times discontinued, postsurgery antidepressants use is only slightly reduced. The Roux-en-Y procedure is most frequently associated with alteration in drug exposure. Medication disintegration, dissolution, absorption, metabolism and excretion have been found to be altered in postbariatric patients, although data are sparse at this time. This paper will review the current evidence regarding the effect of bariatric surgery on drug treatment including mechanism of interference as well as the extent of changes identified to date. Data will be presented as controlled trials followed by case series and reports.

Treating mood disorders in patients with a history of intestinal surgery: a systematic review

Bariatric surgery is increasingly being performed, with the intended benefits of significant and durable weight loss. Radical surgical resection can result in short bowel syndrome (SBS), a rare and devastating condition. Psychological distress is common in these patients. Relevant articles were identified by searching Pubmed and EMBASE databases with the following keywords: 'Bariatrics'[Mesh] OR 'Short Bowel Syndrome' AND 'Antidepressive Agents' OR 'Psychotropic Drugs'[Mesh]. One in-vitro study, four clinical studies and six relevant case reports were identified. Most clinical studies on antidepressant focused on the Roux-en-Y gastric bypass (RYGB); these results are somewhat conflicting for a variety of reasons including different methodologies and small sample sizes. One month after RYGB, in patients receiving serotonin or serotonin/noradrenaline reuptake inhibitors, antidepressant levels decrease to 50% of preoperative levels and return to baseline (or greater) by 6 months in almost all patients. Other pharmacokinetic studies have shown that, 1 year after RYGB, duloxetine and sertraline levels are significantly reduced in comparison with the control population. Paradoxically, in patients with SBS and a few years after surgery, high concentration to dose ratios have been reported for citalopram and escitalopram; this may be because of an intestinal adaptation. Surgery of the intestine is likely to modify absorption and first-pass metabolism of drugs; managing the treatment of depression and anxiety in bariatric and SBS patients therefore presents a major challenge. Close clinical follow-up, associated with therapeutic drug monitoring when available, should enable the optimization of treatment response and modulate the risk of adverse events.

Proximal Roux-en-Y gastric bypass alters drug absorption pattern but not systemic exposure of CYP3A4 and P-glycoprotein substrates

STUDY OBJECTIVES

To evaluate the effect of Roux-en-Y gastric bypass surgery (RYGB) on the pharmacokinetics of midazolam (a CYP3A4 substrate) and digoxin (a P-glycoprotein substrate).

DESIGN

Prospective, nonblinded, longitudinal, single-dose pharmacokinetic study in three phases: presurgery baseline and postoperative assessments at 3 and 12 months.

PATIENTS

Twelve obese patients meeting current standards for bariatric surgery.

MEASUREMENTS AND MAIN RESULTS

At each study visit, patients received a single dose of oral digoxin and midazolam at 8 a.m. Blood samples were collected at regular intervals for 24 hours after dosing. Continuous 12-lead electrocardiogram (EKG), heart rate, blood pressure, and respiratory rate were monitored, and pharmacokinetic parameters from the three visits were compared. The peak plasma concentration (Cmax ) of midazolam increased by 66% and 71% at 3- and 12-month post-RYGB (p=0.017 and p=0.001, respectively), whereas the median time to peak concentration (Tmax ) was reduced by 50%. The mean Cmax for 1'-hydroxymidazolam increased by 87% and 80% at 3 and 12 months (p=0.001 and p<0.001, respectively). However, neither the area under the concentration-time curve (AUC) for midazolam nor the metabolite-to-parent AUC ratio changed significantly over time. For digoxin, the median Tmax decreased from 40 minutes at baseline to 30 and 20 minutes at 3 and 12 months, respectively. The mean AUC for digoxin, heart rate, and EKG patterns were similar across the three study phases.

CONCLUSION

Contemporary proximal RYGB increases the rate of drug absorption without significantly changing the overall exposure to midazolam and digoxin. The Cmax of a CYP3A4 substrate with a high extraction ratio was substantially increased after RYGB.

Tenofovir, emtricitabine, and darunavir/ritonavir pharmacokinetics in an HIV-infected patient after Roux-en-Y gastric bypass surgery

OBJECTIVE

To determine antiretroviral (ARV) pharmacokinetics in a patient who previously underwent Roux-en-Y gastric bypass (RYGB) surgery.

CASE SUMMARY

We describe a 38-year-old Hispanic man who tested positive for human immunodeficiency virus (HIV) 11 months following RYGB surgery. When the patient presented for care of his HIV, his HIV-1 RNA was 146 138 copies/mL (5.20 log) and his CD4 T cell count was 320 cells/mm(3) (25%). He was initiated on tenofovir disoproxil fumarate (TDF) 300 mg once daily, emtricitabine (FTC) 200 mg once daily, and darunavir/ritonavir (DRV/r) 600/100 mg twice daily. ARV concentrations were similar to historical data. Six months following ARV initiation, HIV-1 RNA was <48 copies/mL and CD4 count had increased to 562 cells/mm(3) (39%).

DISCUSSION

Bariatric surgery has been successfully performed in obese persons infected with the HIV, but data are limited on ARV drug selection and pharmacokinetics in this group. Optimal suppression of HIV replication requires appropriate concentrations of ARV drugs, and in a patient who has undergone RYGB, this can be challenging not only because of a decreased absorptive surface area but also because of an increased intragastric pH.

CONCLUSION

We found that once daily TDF/FTC and twice daily DRV/r produced trough concentrations similar to historic data in a patient who previously underwent RYGB with virologic suppression and immunologic recovery.