The effects of gastric bypass surgery on drug absorption and pharmacokinetics

Benefits of uric acid-lowering medication after bariatric surgery in patients with gout

BACKGROUND/PURPOSE

Patients with gout are at risk for increased serum uric acid (SUA) levels and gout attacks in the short term after undergoing bariatric surgery, and the purpose of this study was to evaluate the benefits of short-term treatment with uric acid-lowering medication after bariatric surgery for the control of gout attacks and SUA levels in patients with gout.

METHODS

71 patients who underwent SG from January 2020 to December 2022 were prospectively included. These patients were diagnosed with hyperuricemia before surgery and had a history of gout attacks. Patients were classified into a drug-treatment group (DTG, n = 32) and a non-drug-treatment group (NDTG, n = 39) according to whether they took uric acid-lowering medication after surgery. Changes in the number of gout attacks, body mass index (BMI), and SUA levels at 1 week, 1 month, 3 months, and 6 months after bariatric surgery were measured in both groups.

RESULTS

In the DTG, 22 patients (68.8%) experienced an increase in SUA within 1 week, 3 patients (9.4%) had an acute attack of gout within the first month, and no patients had a gout attack thereafter. In the NDTG, 35 patients (89.7%) experienced an increase in SUA within 1 week, 7 patients (17.9%) had an acute gout attack within the first month, and 4 patients (10.3%) experienced gout attacks between month 1 and month 3 postoperatively. Both groups were free of gout attacks between the 3rd and 6th postoperative month and showed a significant decrease in SUA and BMI by the sixth month.

CONCLUSION

In patients with gout, continued use of uric acid-lowering medication after bariatric surgery is beneficial in reducing the number of gout attacks and the risk of rising SUA.

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.

Comparison of the Onset of Action, Maintenance, and Recovery of Three Weight-based Dosing of Cisatracurium in Patients with Morbid Obesity in Laparoscopic Bariatric Surgery: A Randomized Clinical Trial

Background

For patients with morbid obesity, different cisatracurium dosage regimens are recommended. This study aimed to compare the onset of action, the sufficiency of neuromuscular blockade during infusion, and the recovery of the three distinct cisatracurium dosage scalars in patients with morbid obesity undergoing laparoscopic bariatric surgery.

Methods

In this randomized clinical trial, 55 patients were scheduled for bariatric surgery at Firoozgar Hospital from March 2020 to August 2021. Using a block randomization method, they were randomly divided into three groups, based on total body weight (TBW group), fat-free mass (FFM group), or ideal body weight (IBW group), to receive a bolus of cisatracurium 0.2 mg/Kg, followed by an infusion of 2 µg/Kg, to maintain a train-of-four (TOF) count≤2. Data were analyzed using SPSS software. P<0.05 was considered statistically significant.

Results

The mean time (seconds) to reach TOF0 in the TBW group was significantly shorter (201.89, 95%CI=192.99-210.79; P=0.004) than the IBW group (233.53, 95%CI=218.71-248.34; P=0.01). However, this difference was not statistically significant between TBW and FFM groups (220.83, 95%CI=199.73-241.94; P=0.81) or between FFM and the IBW groups (P=0.23). The rescue dose and increments of cisatracurium infusion were not required in the TBW group, whereas their probability was 4.81 times higher in the IBW group than the FFM group. Furthermore, the TBW and FFM groups had higher mean surgical condition scores than the IBW group (P<0.001, and P=0.006, respectively).

Conclusion

Cisatracurium loading and infusion dosing based on FFM provide a comparable onset of action and surgical field condition to the TBW-based dosing with a shorter recovery time. However, IBW-based dosing of cisatracurium was insufficient for laparoscopic bariatric surgery.Trial Registration Number: IRCT20151107024909N9.A preprint of this study was published at . doi: .

PBPK Modeling of Azithromycin Systemic Exposure in a Roux-en-Y Gastric Bypass Surgery Patient Population

In this investigation, PBPK modeling using the Simcyp® Simulator was performed to evaluate whether Roux-en-Y gastric bypass (RYGB) surgery impacts the oral absorption and bioavailability of azithromycin. An RYGB surgery patient population was adapted from the published literature and verified using the same probe medications, atorvastatin and midazolam. Next, a PBPK model of azithromycin was constructed to simulate changes in systemic drug exposure after the administration of different oral formulations (tablet, suspension) to patients pre- and post-RYGB surgery using the developed and verified population model. Clinically observed changes in azithromycin systemic exposure post-surgery following oral administration (single-dose tablet formulation) were captured using PBPK modeling based on the comparison of model-predicted exposure metrics (Cmax, AUC) to published clinical data. Model simulations predicted a 30% reduction in steady-state AUC after surgery for three- and five-day multiple dose regimens of an azithromycin tablet formulation. The relative bioavailability of a suspension formulation was 1.5-fold higher than the tablet formulation after multiple dosing. The changes in systemic exposure observed after surgery were used to evaluate the clinical efficacy of azithromycin against two of the most common pathogens causing community acquired pneumonia based on the corresponding AUC24/MIC pharmacodynamic endpoint. The results suggest lower bioavailability of the tablet formulation post-surgery may impact clinical efficacy. Overall, the research demonstrates the potential of a PBPK modeling approach as a framework to optimize oral drug therapy in patients post-RYGB surgery.

Micronutrient Supplementation and Bone Health After Prophylactic Total Gastrectomy in Patients With CDH1 Variants

INTRODUCTION

Patients with germline variants in CDH1 who undergo prophylactic total gastrectomy (TG) are at risk of altered nutrient and drug absorption due to modified gastrointestinal anatomy. Bone mineral density loss and micronutrient deficiencies have not been described previously in this patient population.

METHODS

In this study we included 94 patients with germline CDH1 variants who underwent prophylactic TG between October 2017 and February 2022. We examined pre- and post-gastrectomy bone mineral density (BMD); serum biomarkers including calcium, phosphorus, alkaline phosphatase, and 25 (OH)-vitamin D; and postoperative adherence to calcium and multivitamin supplementation.

RESULTS

Almost all patients (92/94, 98%) lost a substantial amount of weight post-TG, with an average weight loss of 26.5% at 12 months post-surgery. Serum biomarkers of mineral metabolism, namely calcium and phosphorus, did not change significantly after TG. However, average BMD was decreased in all patients at 12 months post-TG. Nonadherence to calcium supplementation was associated with a decrease in BMD. Nonadherence to multivitamin supplementation was associated with greater percent BMD loss in the femoral neck and total hip.

CONCLUSIONS

Appropriate micronutrient supplementation and nutritional counseling pre- and postoperatively in patients undergoing prophylactic TG are important to mitigate the long-term effects of gastrectomy on bone health.

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.

Plasma concentrations of SSRI/SNRI after bariatric surgery and the effects on depressive symptoms

Background

Depression and treatment with antidepressants SSRI/SNRI are common in people with morbid obesity who are candidates for bariatric surgery. There is few and inconsistent data about the postoperative plasma concentrations of SSRI/SNRI. The aims of our study were to provide comprehensive data about the postoperative bioavailability of SSRI/SNRI, and the clinical effects on depressive symptoms.

Methods

Prospective multicenter study including 63 patients with morbid obesity and therapy with fixed doses of SSRI/SNRI: participants filled the Beck Depression Inventory (BDI) questionnaire, and plasma levels of SSRI/SNRI were measured by HPLC, preoperatively (T0), and 4 weeks (T1) and 6 months (T2) postoperatively.

Results

The plasma concentrations of SSRI/SNRI dropped significantly in the bariatric surgery group from T0 to T2 by 24.7% (95% confidence interval [CI], -36.8 to -16.6, p = 0.0027): from T0 to T1 by 10.5% (95% 17 CI, -22.7 to -2.3; p = 0.016), and from T1 to T2 by 12.8% (95% CI, -29.3 to 3.5, p = 0.123), respectively.There was no significant change in the BDI score during follow-up (-2.9, 95% CI, -7.4 to 1.0; p = 0.13).The clinical outcome with respect to SSRI/SNRI plasma concentrations, weight change, and change of BDI score were similar in the subgroups undergoing gastric bypass surgery and sleeve gastrectomy, respectively. In the conservative group the plasma concentrations of SSRI/SNRI remained unchanged throughout the 6 months follow-up (-14.7, 95% CI, -32.6 to 1.7; p = 0.076).

Conclusion

In patients undergoing bariatric surgery plasma concentrations of SSRI/SNRI decrease significantly by about 25% mainly during the first 4 weeks postoperatively with wide individual variation, but without correlation to the severity of depression or weight loss.

Association between bariatric surgery and outcomes in chronic myeloid leukemia

BACKGROUND

Bariatric surgery is the most effective weight loss intervention. However, it can also decrease the bioavailability of oral medications. Tyrosine kinase inhibitors, the mainstay treatment for chronic myeloid leukemia (CML), are the most successful example of an oral targeted therapy. The impact of bariatric surgery on CML outcomes is unknown.

METHODS

In a retrospective analysis, we screened 652 patients with CML and identified 22 with prior bariatric surgery, and compared their outcomes to a matched cohort of 44 patients with no prior bariatric surgery.

RESULTS

The rate of early molecular response (3-month BCR::ABL1 < 10% International Scale) was lower in the bariatric surgery group compared with the control group (68% vs. 91%; p = .05), with longer median times to achieve complete cytogenetic (6 vs. 3 months; p = .001) or major molecular responses (12 vs. 6 months; p = .001). Bariatric surgery was associated with inferior event-free survival (5-year, 60% vs. 77%; p = .004) and failure-free survival (5-year, 32% vs. 63%; p < .0001). In a multivariate analysis, bariatric surgery was the only independent predictor for the risk of treatment failure (hazard ratio, 9.40; 95% CI, 2.71-32.55; p = .0004) or event-free survival (hazard ratio, 4.24; 95% CI, 1.67-12.23; p = .008).

CONCLUSIONS

Bariatric surgery is associated with suboptimal responses that require adapted treatment strategies.

Multiple-dose up-titration study to evaluate the pharmacokinetics, safety and antitumor activity of apatinib in advanced gastric adenocarcinoma

Background and purpose

The objective of this study was to investigate the pharmacokinetics, safety, and antitumor activity of apatinib, a vascular endothelial growth factor receptor 2 inhibitor, in advanced gastric adenocarcinoma or gastroesophageal junction adenocarcinoma and evaluate the effect of dose titration on dosage optimization for individual patients.

Methods

Patient with advanced gastric adenocarcinoma progressed after at least one line of chemotherapy were enrolled. Apatinib was given orally once daily starting at 500 mg for 14 days, then up-titrated to 750 mg for 14 days, and then proceeded to a maximum dose of 850 mg. Dose up-titration determination was based on toxicity. The 28-day treatment cycles continued until disease progression, intolerable toxicities, withdrawal of consent, or investigator’ decision.

Results

A total of 60 patients were enrolled, with 17, 18, and 25 patients receiving a maximum dose of 500 mg, 750 mg, and 850 mg, respectively. The pharmacokinetic parameters varied considerably, with the interpatient coefficient of variation for steady state areas under the plasma concentration time curve (AUCss) and the mean maximum concentration of both &gt; 50%. During 500 mg and 750 mg dosing stage, drug exposures in patients with a maximum dosage of 850 mg were lower than in those not titrated to 850 mg. Patients with total gastrectomy exhibited significantly lower AUCss than patients with partial or no gastrectomy (p = 0.004 and 0.032, respectively). Toxicities were tolerable, and disease control rate was 39.5% (95% CI 25.0%−55.6%).

Conclusions

Apatinib dose titration based on toxicity could be used in clinical practice to provide optimal dosage for individual patients.

Clinical Trial registration

https://clinicaltrials.gov/ct2/show/NCT02764268?term=NCT02764268&amp;draw=2&amp;rank=1, NCT02764268.

Evaluation of phenoconversion phenomenon in obese patients: the effects of bariatric surgery on the CYP450 activity "a protocol for a case-control pharmacokinetic study"

Personalized therapy suggests the appropriate drug at the right dose for the first time through genotype-based individualized therapy, instead of prescribing medicines by the traditional one-size-fits-all manner, thereby claiming that it will make medicines safer and more effective. Accordingly, polymorphisms of drug metabolizing enzymes (DMEs), which induce inter-individual variability in the pharmacokinetics of a drug, have attracted great interest in the context of personalized medicine. Obesity is one of the most common chronic diseases in the world, including Iran, and the prevalence is increasing according to predictions. The remarkable role of P450 cytochromes has been verified in the metabolism of numerous drugs, toxins, carcinogen compounds, and the synthesis of some intrinsic compounds, such as steroid hormones. Thus, evaluating the activity of these enzymes is of great importance because any functionality variation can lead to failure in the treatment or unwanted side effects of some drugs. Therefore, any change in the activity of these enzymes in obese patients can also be problematic in the treatment process of these patients in comparison to normal weighted ones. Since only a few human studies have examined the role of inflammation in altering the function of these enzymes, it seems to be necessary to investigate the effect of obesity on the expression and activity of these enzymes; in which the role of inflammatory processes has been proven. Most importantly, it is worth evaluating changes in the activity levels of cytochrome P450 (CYP450) and the inflammatory cytokines after a course of post-surgical treatment and weight loss. To evaluate the activity of CYPs, a multi-drug cocktail is prescribed to obese patients before and after obesity surgery, as well as to healthy volunteers, to provide simultaneous evaluation of different isoforms. A complete demographic data, medical examinations, laboratory tests, and the CYPs genotype of all participants can be extremely important during this investigation.

The effect of weight reduction surgery on the efficacy and tolerability of epilepsy pharmacotherapy

BACKGROUND

Bariatric surgery is an increasingly utilized procedure among patients with obesity-related medical complications. The impact of bariatric surgery on seizure frequency and antiseizure drug (ASD) levels are not well described.

METHODS

We conducted a retrospective chart review of adult patients with a history of epilepsy or seizures undergoing bariatric surgery for morbid obesity from September 1997-September 2019. The median follow-up was 60 months [range 9-220 months].

RESULTS

Forty-six patients with a history of seizures were identified (38 female); 44 patients had recurrent and unprovoked seizures. Seventeen sets of pre- and post-surgery drug concentrations from 14 patients were reviewed. The median age at surgery was 44 years (range, 19-68). Thirty-three patients were prescribed ASDs at the time of bariatric surgery (median 1 drug [range, 1-3]). Laparoscopic Roux-en-Y was performed in 40 patients, and sleeve gastrectomy in 6 patients. Median pre-surgery weight was 120.75 kg (range, 71-230) and BMI 44.4 kg/m2 (range, 34-77.6). Six months following surgery the median weight was 89.5 kg (range, 58.2-202) and BMI 34.2 kg/m2 (range, 24.5-61.9). Nine patients (19.6%) had a worsening of seizure control on long-term follow-up (median 60, range 9-220 months) following bariatric surgery, including five (10.8%) who suffered seizures within 6 months of bariatric surgery. Five patients developed ASD-associated side effects following bariatric surgery including irritability in two patients (levetiracetam and phenytoin) and one patient each suffering from somnolence (phenytoin), hyperammonemic encephalopathy (sodium valproate), and nausea and vomiting (carbamazepine). Subtherapeutic post-surgery drug concentrations were identified in 5 patients and supratherapeutic concentrations in one patient. In the initial 6 months following surgery, ASD doses were increased in five patients and reduced in five.

CONCLUSIONS

The majority of patients with epilepsy who undergo bariatric surgery have no change in seizure frequency. However, a significant minority of patients may experience medication side effects or an increase in seizure tendency due to the impact of bariatric surgery on ASD drug absorption and metabolism leading. Pre- and post-surgical serum concentrations should be measured in patients with seizures or epilepsy receiving ASDs.

Effect of Roux-en-Y gastric bypass on the pharmacokinetic-pharmacodynamic relationships of liquid and controlled-release formulations of oxycodone

The physiological changes following Roux-en-Y gastric bypass (RYGB) surgery may impact drug release from mechanistically different controlled-release tablets, making generic substitution inappropriate. This study aimed to characterise the pharmacokinetic-pharmacodynamic relationships of oxycodone from a lipid-based and water-swellable controlled-release tablet in RYGB patients. Twenty RYGB patients received 10-mg oral solution oxycodone or 20-mg controlled-release (water-swellable or lipid-based) oxycodone in a three-way, randomised, semiblinded and cross-over study. Blood sampling and pupillary recordings were conducted over a 24-h period. A previously established pharmacokinetic-pharmacodynamic model of these three formulations in healthy volunteers was used in the analysis as a reference model. No differences in absorption kinetics were seen between controlled-release formulations in patients. However, the absorption lag time was 11.5 min in patients vs 14 min in healthy volunteers for controlled-release tablets (P < 0.001). Furthermore, oral bioavailability was 14.4% higher in patients compared to healthy volunteers regardless of formulation type (P < 0.001). Oxycodone pharmacodynamics were not significantly affected by formulation or patient status. However, baseline pupil diameter was inversely correlated with age (P < 0.001) and plasma concentrations of oxycodone at half-maximum effect were 31% lower in males compared to females (P < 0.05). Generic substitution of monophasic lipid-based and water-swellable controlled-release oxycodone tablets may be considered safe in RYGB patients.

Subtherapeutic posaconazole prophylaxis in a gastric bypass patient following hematopoietic stem cell transplantation

PURPOSE

A case of invasive fungal infections (IFIs) with subtherapeutic posaconazole prophylaxis in a gastric bypass patient following hematopoietic stem cell transplantation (HSCT) is reported.

SUMMARY

A 52-year-old malnourished male with a medical history of Roux-en-Y gastric bypass for obesity developed acute myelogenous leukemia and underwent allogeneic HSCT approximately 17 months later. He was admitted 1 month after HSCT for failure to thrive and initiated on parenteral nutrition due to worsening diarrhea and suspected gastrointestinal graft-versus-host disease (GI GVHD). During admission, the patient was continued on daily oral posaconazole for antifungal prophylaxis and was found to have subtherapeutic posaconazole and deficient vitamin levels, likely secondary to his gastrojejunostomy and increased gastric transit time. The oral posaconazole was altered to twice-daily dosing in an effort to increase serum drug levels and prevent IFIs.

CONCLUSION

Patients with a history of gastric bypass are at increased risk for malabsorption of oral posaconazole and nutrients, especially following HSCT with suspected GI GVHD.

Antiseizure Medication use in Gastric Bypass Patients and Other Post-Surgical Malabsorptive States

Healthcare professionals are encountering an increasing number of patients who have undergone bariatric surgeries. Antiseizure medications (ASM) have a narrow therapeutic window, and patients with malabsorptive states receiving ASM present a complex situation as the pharmacokinetics of these drugs have only been studied in patients with a normal functioning gastrointestinal tract. Patients with malabsorptive states may have altered pharmacokinetics, and there is limited literature to guide drug selection and dosage adjustment in patients with malabsorptive states. This review highlights pharmacokinetic parameters of common ASM, and considerations when managing patients on them. The effect of pH, lipophilicity, absorption, and metabolism should be taken into account when selecting and managing ASMs in this patient population. Based on these parameters, levetiracetam, and topiramate have fewer issues referable to absorption related to bariatric surgery while oral formulations of phenytoin, carbamazepine, oxcarbamazepine and valproic acid have reduced absorption due to effects of bariatric surgery based on the pharmacokinetic properties of these medications. Extended formulations should be avoided and ASM serum concentrations should be checked before and after surgery. The care of patients with epilepsy who are scheduled to undergo bariatric surgery should be guided by a multidisciplinary team including a pharmacist and a neurologist who should be involved in the adjustment of the ASMs throughout the pre-surgical and post-surgical periods.

How I treat obesity and obesity related surgery in patients with chronic myeloid leukemia: An outcome of an ELN project

Obesity may affect treatment outcome in CML patients, therefore the treatment of this cohort of patients need careful monitoring, TKIs dose adjustment may be required for certain patients. Further studies are needed to determine the proper TKIs doses.

Is it possible to use Proton Pump Inhibitors in COVID-19 treatment and prophylaxis?

Coronaviruses (CoV), discovered after 1960, caused human life-threatening outbreaks. SARS-CoV2, which appeared in Wuhan, China in December 2019, causing Severe Acute Respiratory Syndrome and has different features than other coronaviruses, has been determined and the disease caused by the virus has been called "Coronavirus Disease-2019" (COVID-19). This disease activates both the natural and acquired immune system. The cytokin storm, in which blood levels of proinflammatory cytokines are detected excessively high is developing and the uncontrolled inflammatory response causes local and systemic tissue damages. Although a spesific drug has not been found yet, the medications currently in use for other indications, whose pharmacokinetic- pharmacodynamic properties and toxic doses are already known; are included in the treatment practice of COVID-19. These drugs affect the entry of the virus into the cell and its intracellular distribution. They also have anti-inflammatory and immunomodulating effects too. Therefore, we think that Proton Pump Inhibitors (PPI's) with similar mechanisms of action may also be involved in COVID-19 treatment and prophylaxis.

Safety of Bariatric Surgery in Morbidly Obese Patients with Human Immunodeficiency Virus: A Nationwide Inpatient Sample Analysis, 2004-2014

Background: Despite rising rates of obesity among human immunodeficiency virus (HIV)-positive individuals, the safety and tolerability of surgery in this population have not been established. The primary aim of this study was to examine the safety of bariatric surgery and rate of in-hospital postoperative complications in morbidly obese patients with HIV. Materials and Methods: The U.S. Nationwide Inpatient Sample database was queried between 2004 and 2014 for discharges with codiagnoses of morbid obesity and bariatric surgery. The primary outcome was in-hospital mortality. Secondary outcomes included length of stay, hospitalization costs, and multiple categories of complications, including systemic complications, surgical complications, and nutritional and behavioral complications. Results: Among 267,082 patients with discharge diagnoses of morbid obesity and bariatric surgery, 346 (0.13%) were diagnosed with HIV. On multivariable analysis, HIV did not influence in-hospital mortality (p = 0.530). HIV was not associated with increased risk of renal failure (p = 0.274), thromboembolism (p = 0.713), myocardial infarction (p = 0.635), sepsis (p = 0.757), hemorrhage (p = 0.303), or wound infection (p = 0.229). Other measured surgical complications were not significantly different (p > 0.05). Notably, HIV-positive patients had an increased risk for postoperative pneumonia (p = 0.002), pancreatitis (p = 0.049), and thiamine deficiency (p = 0.016). Conclusion: Bariatric surgery among HIV-positive patients appears to be acceptably safe with the risk of postoperative complications comparable with non-HIV patients.

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.

Low hydroxychloroquine blood levels in patients who have had gastric bypass surgery

Gastric bypass surgery, also called Roux-en-Y gastric bypass (RYGB), can result in the malabsorption of medications, requiring the use of higher than usual doses in order to achieve a therapeutic effect. We describe the results of hydroxychloroquine (HCQ) blood levels in three patients with systemic autoimmune disease taking standard HCQ doses and their associated disease activity levels. This is a retrospective review of all patients who had undergone RYGB and were taking HCQ in a rheumatology community-based practice. Two patients with SLE and one patient with primary Sjogren's syndrome had previously undergone RYGB. All three had subtherapeutic HCQ blood levels and active disease. Increasing their HCQ doses above the recommended 400 mg a day dosing resulted in therapeutic HCQ levels in all three patients and better disease control in two of the three patients. RYGB patients may not absorb HCQ adequately, resulting in subtherapeutic HCQ blood levels and inadequate disease control. Patients who have undergone RYGB and are taking HCQ should have drug levels monitored. RYGB patients may require higher than recommended doses of HCQ in order to achieve better disease control and avoid unneeded additional immunosuppressive agents.

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.

Effect of Roux-en-Y gastric surgery on ciprofloxacin pharmacokinetics: an obvious effect?

PURPOSE

To evaluate pharmacokinetic parameters of ciprofloxacin in patients undergoing Roux-en-Y gastric surgery (RYGS).

METHODS

Controlled, single-dose, open-label study in patients undergoing RYGS. Healthy overweight/obese patients 18-60 years old were included. The assessment was performed once in control patients and three times in case patients (before surgery and 1 and 6 months after surgery). In each visit, the subjects received a single oral dose of ciprofloxacin 500 mg. Venous blood samples were obtained at baseline and 0.5, 1, 1.25, 1.5, 1.75, 2, 2.5, 3, 4, 8 and 14 h after ciprofloxacin intake. Pre- and post-surgery variables were compared using paired ANOVA or the Wilcoxon tests and control vs cases using ANOVA or Mann Whitney. Given the post-surgery change in body weight, the parameters were corrected by dose (mg)/body weight (kg). The analysis was performed using SPSS.

RESULTS

Ciprofloxacin C_max was significantly reduced 1 month after surgery (1840.9 ± 485.2 vs 1589.6 ± 321.8 ng/ml; p = 0.032) but not 6 months after. C_max on the sixth month was lower than C_max in control group (2160.4 ± 408.6 vs 1589.6 ± 321.8 ng/ml; p < 0.001). After correcting by the dose (mg)/patient's body weight, both C_max and AUClast showed significant decrease 1 and 6 months after surgery: C_max, 289.1 ± 65.3 and 263.5 ± 52.1 (ng/ml)/(dose (mg)/weight (kg)) respectively vs 429.3 ± 127.6 (ng/ml)/(dose (mg)/weight (kg)) at baseline; AUC, 1340.6 ± 243.0 and 1299.2 ± 415.4 (h × ng/ml)/(dose (mg)/weight (kg)) respectively vs 1896.7 ± 396.8 (h × ng/ml)/(dose (mg)/weight (kg)) at baseline. C_max 1 month post-surgery showed lower values than the control group (375.4 ± 77.4 vs 263.5 ± 52.1 ng/ml; p < 0.001).

CONCLUSION

Ciprofloxacin absorption is impaired 1 month and 6 months after RYGS. The effect on C_max and AUClast faded on the sixth month due to weight loss. It is no necessary to modify the doses of ciprofloxacin in these patients.

Immunosuppressive drugs and the gastrointestinal tract in renal transplant patients

Gastrointestinal (GI) discomfort is common after renal transplantation and can be caused by the use of various immunosuppressive drugs. GI symptoms affect the quality of life, lead to an impaired graft survival and an increased mortality. Moreover, diseases and disturbances of the GI tract also affect the pharmacokinetics of immunosuppressive drugs. This review addresses the interaction between immunosuppressive agents and GI disorders. The GI tract is involved in the metabolism of several immunosuppressive drugs. Calcineurin inhibitors, mTor inhibitors, and corticosteroids are subjected to metabolism by the intestinal cytochrome P450 (CYP3A) and by the drug efflux pump ABCB1. Mycophenolate is partly metabolized in the stomach and intestine and undergoes enterohepatic recirculation. Gastrointestinal disturbances can lead to a modified exposure to immunosuppressive drugs. In the first and second part of this review, we focus on the role of the GI tract in the pharmacokinetics of the immunosuppressive drugs and how to adjust immunosuppressive therapy in patients with vomiting, need for tube feeding, delayed gastric emptying, intestinal resection, and diarrhea. In the third part, we review the GI adverse effects of the various immunosuppressive drugs, with special attention for diarrhea and dyspepsia. Finally, we discuss the effects of drugs used for relief of GI complaints on the exposure to immunosuppressive agents.

A gastrointestinal simulation system for dissolution of oral solid dosage forms before and after Roux-en-Y gastric bypass

Background

The Roux-en-Y gastric bypass (RYGB) is a bariatric procedure, greatly reducing the stomach size and bypassing the duodenum and proximal jejunum. Hence, RYGB may reduce the absorption and bioavailability of oral medication. For clinical decisions on the use of medication, knowledge of altered modifications in drug disposition is a prerequisite. An in vitro dissolution method for solid oral medications, simulating conditions before and after RYGB, might be a valuable tool to predict the pharmaceutical availability of medicines frequently used by patients after RYGB.

Objectives

To develop a gastrointestinal simulation system (GISS), mimicking conditions before and after RYGB for investigating dissolution characteristics of solid oral medications, and to assess the pharmaceutical availability of metoprolol from immediate-release (IR) and controlled-release (CR) tablets under these conditions.

Methods

With an adjusted, pharmacopoeial paddle dissolution apparatus, the GISS enables variation in parameters which are relevant to drug release in vivo: pH, volume, residence time, osmolality and agitation. Metoprolol tartrate 100 mg IR tablets and metoprolol CR tablets were tested. Release profiles were determined by measuring the concentrations of metoprolol spectrophotometrically.

Results

From IR tablets, under all conditions applied, >85% of metoprolol was released within 25 min. From all tested CR tablets >90% of metoprolol was released after 22 hours.

Conclusions

This GISS is a suitable dissolution system to assess pharmaceutical availability before and after RYGB. In patients who have undergone RYGB, no problems in pharmaceutical availability of metoprolol IR and CR tablets are to be expected. Any changes in response to metoprolol in patients after RYGB should therefore be ascribed to changes in bioavailability.

Drug Dosing in Obese Children: Challenges and Evidence-Based Strategies

With the alarming increase of obesity in children, pediatricians are increasingly being confronted with difficult dosing decisions. Many drug labels do not provide specific dosing instructions for children who are obese. In this article, we describe the physiologic parameters altered by obesity and their influences on drug disposition and effect. We review the principles of allometry, and the key pharmacokinetic parameters that can be used to derive age appropriate dosing regimens. Last, we illustrate how appropriate weight descriptors can be selected, and how important PK parameters can be extrapolated for dosing in obese children when pediatric pharmacokinetic information is available.

Antithrombotic therapy in obesity

Clinical management of obese subjects to reduce their risk of suffering cardiovascular events is complex. Obese patients typically require preventive strategies, life-style modifications, and multi-drug therapy to address obesity-induced co-morbidities. Data regarding the effects of excess weight on the pharmacokinetics of most drugs is scarce as these individuals are often excluded from clinical trials. However, the physiological alterations observed in obese patients and their lower response to some antiplatelet agents and anticoagulants have suggested that dosage regimes need to be adjusted for these subjects. In this review we will briefly discuss platelet alterations that can contributeto increased thrombotic risk, analyse existing data regarding the effects of obesity on drug pharmacokinetics focusing on antiplatelet agents and anticoagulants, and we will describe the beneficial effects of weight loss on thrombosis.

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.

Influences of Obesity and Bariatric Surgery on the Clinical and Pharmacologic Profile of Rivaroxaban

The health implications of obesity are myriad and multifaceted. Physiologic changes associated with obesity can affect the absorption, distribution, metabolism, and excretion of administered drugs, thereby altering their pharmacologic profiles. In 2016, the Scientific and Standardization Committee of the International Society on Thrombosis and Haemostasis published recommendations about the use of direct oral anticoagulants (DOACs) in obese patients. This guidance provides uniform recommendations for all DOACs, yet data suggest that individual agents may be affected to different degrees by obesity. Moreover, there are no recommendations currently available to guide DOAC use in bariatric surgery patients, in whom anatomic and physiologic changes to the digestive system can influence drug pharmacokinetics. Our review of the available literature indicates that the clinical profile of the DOAC rivaroxaban is not affected by high weight or bariatric surgery; hence, it does not appear that rivaroxaban dosing needs to be altered in these patient populations.

Morphine and metabolites plasma levels after administration of sustained release morphine in Roux-en-Y gastric bypass subjects versus matched control subjects

BACKGROUND

Better knowledge of opioid pharmacology after Roux-en-Y gastric bypass (RYGB) is required for optimizing their use in this growing population.

OBJECTIVE

The aim of this case-controlled pharmacokinetic (PK) study was to compare morphine and its glucuronidated metabolites (morphine-3-glucuronide and morphine-6-glucuronide) plasma PKs between patients with RYGB and their controls.

SETTINGS

University hospital, Lariboisière Hospital, Paris.

METHODS

Thirty milligrams of morphine as a sustained-release formulation was orally administered in 12 women who had undergone RYGB for at least 2 years (RYGB group) and in their nonsurgical controls matched for sex, body mass index (±2 points), and age (±5 yr). Morphine, morphine-3-glucuronide, and morphine-6-glucuronide plasma concentrations over a 12-hour period were determined by a validated method using liquid chromatography mass spectrometry in tandem. Drowsiness, respiratory rate, and oxygen saturation were monitored during the PK visit.

RESULTS

Morphine oral area under the curve (for time 0-12 hr; 115.8 ± 108.0 nmol.hr/L and 86.9 ± 38.8 nmol.hr/L for RYGB group and control group, respectively, P = .71), morphine at maximal concentration, metabolites oral area under the curve (for time 0-12 hr)_, and other PK parameters were similar between groups. After drug administration, mean drowsiness was superior in RYGB group. Mean respiratory rate and oxygen saturation were similar in both groups.

CONCLUSION

No dose adjustment seems to be needed for sustained release morphine when prescribed to RYGB patients.

Cure with ledipasvir/sofosbuvir for chronic hepatitis C virus in an individual with gastric bypass

WHAT IS KNOWN AND OBJECTIVE

The impact of gastric bypass surgery on the pharmacokinetics of various medications has been reported. Presently, no data exist for the treatment of chronic hepatitis C virus with ledipasvir/sofosbuvir (LDV/SOF) in an individual with a history of gastric bypass.

CASE DESCRIPTION

We report the successful cure of an individual who was treated with LDV/SOF who had a history of gastric bypass. The patient tolerated LDV/SOF well while only experiencing a minor headache.

WHAT IS NEW AND CONCLUSION

Ledipasvir/sofosbuvir treatment may still be effective in those with a history of gastric bypass surgery.

The pharmacokinetics of oral ketoprofen in patients after gastric resection

BACKGROUND

Total and partial gastric resection may affect the pharmacokinetics of drugs, especially orally administered a few days after surgery. Ketoprofen is a non-steroidal anti-inflammatory drug (NSAID) broadly used to treat postoperative pain, including patients after gastric resection. The aim of the research was to analyse the pharmacokinetics (PK) of orally administered ketoprofen in patients after gastrectomy.

METHODS

The research was carried out on two groups of patients after total (TG; Roux-Y procedure) and partial (PG; Billroth II procedure) gastrectomy. The patients in group TG (n=15; mean [SD] age 61.86 [14.15] years; and BMI 24.20 [3.73] kg/m²) and group PG (n=5; mean [SD] age 62.40 [16.80] years; and BMI 23.98 [3.45] kg/m²) received ketoprofen in a single oral dose of 100mg. The measurement of ketoprofen plasma concentrations was made by means of the HPLC (high performance liquid chromatography) method.

RESULTS

The PK parameters in group TG and PG were as follows: maximum plasma concentration (C_max), 3.42 [0.99] and 4.66 [0.81] mg/l (p=0.0220); area under the plasma concentration-time curve from zero to infinity (AUC_0-∞), 9.12 [2.78] and 9.17 [2.87] mg×h/ml (p=0.9734); area under the first moment curve from zero to the time of infinity (AUMC_0-∞), 25.95 [8.52] and 26.53 [11.43] mg×h²/l (p=0.9056); time to reach maximum concentration (t_max), 0.47 [0.25] and 0.55 [0.27] h (p=0.5327), respectively.

CONCLUSIONS

Lower concentrations of ketoprofen in patients after gastrectomy suggest that it might be necessary to apply higher dose of the analgesic.

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.

Review article: The nutritional and pharmacological consequences of obesity surgery

BACKGROUND

Obesity surgery is acknowledged as a highly effective therapy for morbidly obese patients. Beneficial short-term effects on common comorbidities are practically undisputed, but a growing data pool from long-term follow-up reveals increasing evidence of potentially severe nutritional and pharmacological consequences.

AIMS

To assess the prevalence, causes and symptoms of complications after obesity surgery, to elucidate and compare therapy recommendations for macro- and micronutrient deficiencies, and to explore surgically-induced effects on drug absorption and bioavailability, discussing ramifications for long-term therapy and prophylaxis.

METHODS

PubMed, Embase and MEDLINE were searched using terms including, but not limited to, bariatric surgery, gastric bypass, obesity surgery and Roux-en-Y, coupled with secondary search terms, e.g. anaemia, micronutrients, vitamin deficiency, bacterial overgrowth, drug absorption, pharmacokinetics, undernutrition. All studies in English, French or German published January 1980 through March 2014 were included.

RESULTS

Macro- and micronutrient deficiencies are common after obesity surgery. The most critical, depending on surgical technique, are hypoalbuminemia (3-18%) and deficiencies of vitamins B1 (≤49%), B12 (19-35%) and D (25-73%), iron (17-45%) and zinc (12-91%). Many drugs commonly administered to obese patients (e.g. anti-depressants, anti-microbials, metformin) are subject to post-operative and/or PPI-associated changes affecting bioavailability and absorption.

CONCLUSIONS

Complications are associated with pre-operative and/or post-operative malnutrition or procedure-related changes in intake, absorption and drug bioavailability. The high prevalence of nutrient deficiencies after obesity surgery makes life-long nutritional monitoring and supplementation essential. Post-operative changes to drug absorption and bioavailability in bariatric patients cast doubt on the validity of standard drug dosage and administration recommendations.

Moxifloxacin dosing in post-bariatric surgery patients

INTRODUCTION

Given the ever increasing number of obese patients and obesity related bypass surgery, dosing recommendations in the post-bypass population are needed. Using a population pharmacokinetic (PK) analysis and PK-pharmacodynamic (PD) simulations, we investigated whether adequate moxifloxacin concentrations are achieved in this population.

METHODS

In this modelling and simulation study we used data from a trial on moxifloxacin PK. In this trial, volunteers who had previously undergone bariatric surgery (at least 6 months prior to inclusion), received two doses (intravenous and oral) of 400 mg moxifloxacin administered on two occasions.

RESULTS

In contrast to other papers, we found that moxifloxacin PK were best described by a three compartmental model using lean body mass (LBM) as a predictor for moxifloxacin clearance. Furthermore, we showed that the probability of target attainment for bacterial eradication against a hypothetical Streptococcus pneumoniae infection is compromised in patients with higher LBM, especially when targeting microorganisms with minimum inhibitory concentrations (MICs) of 0.5 mg l(-1) or higher (probability of target attainment (PTA) approaching zero). When considering the targets for suppression of bacterial resistance formation, even at MIC values as low as 0.25 mg l(-1) , standard moxifloxacin dosing does not attain adequate levels in this population. Furthermore, for patients with a LBM of 78 kg or higher, the probability of hitting this target approaches zero.

CONCLUSIONS

Throughout our PK-PD simulation study, it became apparent that, whenever optimal bacterial resistance suppression is deemed necessary, the standard moxifloxacin dosing will not be sufficient. Furthermore, our study emphasizes the need for a LBM based individualized dosing of moxifloxacin in this patient population.

Sleeve gastrectomy is a safe and efficient procedure in HIV patients with morbid obesity: a case series with results in weight loss, comorbidity evolution, CD4 count, and viral load

BACKGROUND

The efficacy and safety of bariatric surgery have been poorly studied in patients affected with HIV. Although sleeve gastrectomy (SG) is the most widely used procedure in many countries, most of the published literature reported results with the gastric bypass (GBP) procedure on morbidly obese HIV patients.

METHODS

We have evaluated retrospectively, in eight consecutive patients who underwent a SG, its effect in weight loss and its impact on the treatment and on the markers of HIV infection.

RESULTS

Seven out of eight patients were females. The mean age was 46 years, with a median preoperative BMI of 42 kg/m(2). The mean duration of HIV infection and CD4 cell count were 13.4 years and 457 cells/mm(3), respectively. The mean weight loss was 37 kg in 20 months, the excess BMI loss was 80.8 ± 30.9 %, and the excess weight loss is 81.5 ± 28.9 % with one minor complication. CD4 counts were unchanged. Three patients had therapy modifications that were unrelated to bariatric surgery. Two patients had a therapeutic drug monitoring before and after the intervention. Plasma concentrations remained in therapeutic levels after the SG. Most comorbidities disappeared postoperatively, decreasing the cardiovascular risk.

CONCLUSIONS

The sleeve gastrectomy was safe and effective with no consequences on CD4 counts and viral load in HIV-affected obese patients. It should be considered as a part of the treatment in morbidly obese HIV patients.

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.