Oral bioavailability of linezolid before and after Roux-en-Y gastric bypass surgery: is dose modification necessary in obese subjects?

The pharmacokinetics of antibiotics in patients with obesity: a systematic review and consensus guidelines for dose adjustments

Obesity can cause physiological changes resulting in antibiotic pharmacokinetic alterations and suboptimal drug exposures. This systematic review aimed to summarise the available evidence on this topic and provide guidance for dose adjustment of antibiotics in adult (age ≥18 years) patients with obesity (BMI >30 kg/m2). We searched PubMed, Embase, and CENTRAL databases to find relevant studies published between database inception and Dec 30, 2023. We initially identified 6113 studies, which became 4654 studies after duplicate removal, and 128 studies were included in the final review. β-lactam antibiotics were most commonly studied (57 studies), followed by the group of glycopeptides, lipoglycopeptides, and oxazolidinones (45 studies). The certainty of evidence was low or very low for all antibiotics and a meta-analysis was not possible due to the heterogeneity of study populations and methods. Obesity modestly alters the pharmacokinetics of β-lactam antibiotics, but evidence does not support routine dose adjustments. For aminoglycosides and glycopeptides, the impact of obesity on pharmacokinetics is evident and weight-based dosing is recommended. Data are sparse for other antibiotic classes and research needs are described. In the absence of robust pharmacokinetic data, therapeutic drug monitoring can be used to guide individualised dosing.

Pharmacokinetics after bariatric surgery: adverse effects and drug safety issues in bariatric patients

INTRODUCTION

Medication management after bariatric surgery is a major and complex challenge. The altered gastrointestinal anatomy/physiology post-surgery may impact oral drug absorption/pharmacokinetics, with potential clinical implications. Along with multiple studies/cases of impaired post-surgery drug absorption/pharmacokinetics, leading to potential treatment failure, reports of increased drug exposure, leading to post-bariatric safety issues and adverse effects risk, are also available; yet, this second scenario of increased post-surgery drug levels, is less familiar in practice.

AREAS COVERED

In this article, we highlight and overview the literature reports of increased post-bariatric drug exposure and safety issues, and discuss the underlying relevant mechanisms. Finally, we provide clinical recommendations for managing this therapeutic challenge.

EXPERT OPINION

Around 25 drugs were found to exhibit post-bariatric enhanced pharmacokinetics and risk of adverse effects. Among them, toxicity with lithium treatment is well-established. Clear safety concerns were also raised for other drugs, including levothyroxine, atorvastatin, paracetamol and, importantly, immediate-release morphine. Cautious use, while closely monitoring clinical signs of toxicity, is advised for these drugs. Realizing the potentially altered post-bariatric pharmacokinetics of various drugs, and, in particular, the risk of increased exposure with related adverse effects, is essential for providing optimal pharmacological therapy and overall patient care to the growing bariatric population.

Clinical Pharmacokinetics of Antitubercular Drugs in the Overweight and Obese Population: Implications for Dosage Adjustments

The rise in global obesity prevalence has increased the need to understand the pharmacokinetics of drugs in overweight and obese individuals. Tuberculosis remains a significant health challenge, and its treatment outcomes can be influenced by the pharmacokinetic profiles of antitubercular agents. This literature review aims to point out the clinical pharmacokinetics of antitubercular drugs in the overweight and obese patient population, highlighting considerations for potential dosage adjustments. We conducted a comprehensive search of the PubMed US National Library of Medicine from inception to January 2024. Articles focusing on the pharmacokinetics of antitubercular agents used for both drug-susceptible and multidrug-resistant tuberculosis in overweight and obese adults were included. In total, 349 scientific articles were identified and examined for human pharmacokinetic parameters. Of these, 19 were included in this article. To highlight potential differences, pharmacokinetic data for normal-weight tuberculosis patients are also presented, albeit selectively. In general, pharmacokinetic studies of antitubercular agents in overweight and obese individuals are lacking. Fixed-dose combinations often used in the treatment of drug-susceptible tuberculosis are not recommended when treating these population groups. Rather, individual dosing based on therapeutic drug monitoring and the known solubility of the substance should be considered. To improve the management of tuberculosis in overweight and obese patients, there is an urgent need for pharmacokinetic studies and, ultimately, adequate dosing in this patient population, especially given the increasing prevalence of obesity.

Varying concentrations of tyrosine kinase inhibitors in chronic myeloid leukemia patients following bariatric surgery: a case series

Bariatric surgery is increasingly performed to treat severe obesity. As a result of anatomical and physiological changes in the gastrointestinal tract, the pharmacokinetics (PK) of oral drugs can be altered, affecting their efficacy and safety. This includes the class of tyrosine kinase inhibitors (TKIs) which are used to treat chronic myeloid leukemia (CML). This case series describes the clinical course of four CML cases with a history of bariatric surgery. The patients used various TKIs (nilotinib, dasatinib, bosutinib, ponatinib, and imatinib) for which 15 drug levels were measured. The measured TKI concentrations were in part subtherapeutic, and highly variable when compared to mean levels measured in the general population. Multiple drug levels were measured in these patients, as the clinicians were aware of the possible impact of bariatric surgery. The drug levels were used as additional input for clinical decision-making. All four patients required TKI switches and/or dose modifications to achieve an effective and tolerable treatment. Eventually, adequate clinical and molecular remissions were achieved in all cases. In summary, TKI concentrations of patients undergoing bariatric surgery may be subtherapeutic. Moreover, there is substantial interindividual and intraindividual variation, which may be explained by the complex interference of bariatric surgery and associated weight loss. For clinical practice, therapeutic drug monitoring is advised in patients with a history of bariatric surgery in case of suboptimal response or loss of response.

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.

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.

Pharmacokinetic changes post-bariatric surgery: A scoping review

Bariatric surgeries induce structural changes that can alter the absorption of drugs in patients already at risk of polypharmacy. This scoping review aimed to explore pharmacokinetic changes of orally administered drugs in patients post-bariatric surgery, and assess the quality and level of bias. Electronic databases were searched for articles relating to bariatric surgery and pharmacokinetics published between 1998 and 2019. Pre-post studies reporting on pharmacokinetic parameters were included, and the Newcastle-Ottawa Scale was used to assess risk-of-bias. A total of 21 studies were included in this review, and changes in absorption were reported in all included studies across 29 drugs. In 11 studies, this change was reported as statistically significant (p<.05), while six reported a nonsignificant change. More drugs exhibited a shorter Tmax and higher Cmax after surgery than otherwise, however changes in AUC were variable. Four studies were assessed as having fair quality while the remainder of the included studies were of good quality and low risk-of-bias. Bariatric surgery alters the absorption of drugs and several mechanisms are implicated to be responsible. Short and long-term monitoring is recommended in patients post-surgery for clinical changes in response to medications. Future research with a higher number of participants and greater control of variables, such as concurrent medications, malabsorptive disorders, and body composition should be considered.

The Effect of Bariatric Surgery on Oral Antibiotic Absorption: a Systematic Review

PURPOSE

The purpose of this study was to conduct a systematic review of the existing literature to determine the effect of bariatric surgery on various pharmacokinetic parameters of oral antibiotic absorption as well as overall patient outcomes.

MATERIALS AND METHODS

MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials (CENTRAL) were searched up to February 2020. Outcomes of interest included change in pharmacokinetic parameters of oral antibiotics administered to patients following bariatric surgery, using variables such as maximum plasma concentration (Cmax), time to reach maximum plasma concentration (Tmax), area under the concentration-time curve (AUC), clearance, and volume of distribution. MINORS and Cochrane risk of bias tools were used to assess quality of evidence.

RESULTS

Ten studies with 100 patients assessing 8 oral antibiotics were included. The majority (77%) of patients underwent Roux-en-Y gastric bypass (RYGB), with fewer undergoing ventral banded gastroplasty (VBG) (14%), jejunoileostomy (6%), and jejunoileal bypass (3%). Antibiotic classes investigated included beta-lactams (5 studies), fluoroquinolones (2 studies), macrolides (2 studies), and oxazolidinones (1 study). Heterogeneity between studies precluded meaningful pooling or meta-analysis of data. Overall risk of bias was fair.

CONCLUSION

Patients given oral beta-lactams and macrolides warrant close monitoring due to unpredictable absorption post-bariatric surgery, whereas oral fluoroquinolones and linezolid may not be affected. Several studies also showed decreased absorption following RYGB, as well as lower serum exposure in patients with obesity compared to non-obese controls. Clinicians should monitor patients on a case-by-case basis for signs of antibiotic failure or toxicity and reassess dosing accordingly.

The influence of bariatric surgery on oral drug bioavailability in patients with obesity: A systematic review

Anatomical changes in the gastrointestinal tract and subsequent weight loss may influence drug disposition and thus drug dosing following bariatric surgery. This review systematically examines the effects of bariatric surgery on drug pharmacokinetics, focusing especially on the mechanisms involved in restricting oral bioavailability. Studies with a longitudinal before-after design investigating the pharmacokinetics of at least one drug were reviewed. The need for dose adjustment following bariatric surgery was examined, as well as the potential for extrapolation to other drugs subjected to coinciding pharmacokinetic mechanisms. A total of 22 original articles and 32 different drugs were assessed. The majority of available data is based on Roux-en-Y gastric bypass (RYGBP) (18 of 22 studies), and hence, the overall interpretation is more or less limited to RYGBP. In the case of the majority of studied drugs, an increased absorption rate was observed early after RYGBP. The effect on systemic exposure allows for a low degree of extrapolation, including between drugs subjected to the same major metabolic and transporter pathways. On the basis of current understanding, predicting the pharmacokinetic change for a specific drug following RYGBP is challenging. Close monitoring of each individual drug is therefore recommended in the early postsurgical phase. Future studies should focus on the long-term effects of bariatric surgery on drug disposition, and they should also aim to disentangle the effects of the surgery itself and the subsequent weight loss.

Systematic review of drug bioavailability following gastrointestinal surgery

PURPOSE

Inter- and intraindividual pharmacokinetics variability in humans affects the way in which drugs act on the body. Gastrointestinal surgery has an impact on this variability and significantly alters the kinetics of drugs in post-surgical patients. The way in which pharmacokinetic profiles are modified depends on the type of operative procedure performed. The extent to which the absorption of different groups of drugs is affected varies according to the site and length of intestinal resections.

METHODS

A literature search was conducted based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol. Three databases were searched: MEDLINE, Embase, and the Cochrane Library. For each drug, potential changes in absorption were described, including recommendations extracted from the results of the studies and collected according to authors' criteria as practical conclusions, and grades of recommendation were determined by levels of evidence using the Oxford Centre for Evidence-Based Medicine scale.

RESULTS

Sixty-eight articles were collected during the selection process after the bibliographic search. The main outcomes for 60 drugs from the various studies were classified according to each type of surgery.

CONCLUSIONS

Modifications in the digestive tract secondary to gastrointestinal surgery may compromise the bioavailability of drugs. Decreased absorption surface, gastric emptying speed, and gastric pH alteration are factors to be taken into account in the management of pharmacological treatment after surgery. Evidence supported by data in clinical practice is scarce, but after studying the pharmacokinetic profile of some molecules, it is possible to offer recommendations for its adaptation to the patient's clinical situation.

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.

Pharmacokinetics of Tedizolid in an Obese Patient after Bariatric Surgery

An obese woman was treated with oral tedizolid 200 mg once daily for pseudoarthrosis 10 years after Roux-en-Y bypass surgery. Total plasma peak concentration was 2.12 mg/liter 3 h after intake, and area under the concentration-time curve from 0 to 24 h (AUC0-24) was 28.3 mg/liter · h. The AUC0-24/MIC ratio for unbound concentrations and for sensitive Staphylococcus and Streptococcus strains was ≥10.8, higher than the target ratio of 3. These results support the use of tedizolid without adjustment after bariatric surgery.

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.

Systematic Therapeutic Drug Monitoring for Linezolid: Variability and Clinical Impact

Linezolid serum trough (C_min) and peak (C_max) levels were determined prospectively in 90 patients. Adequate exposure was defined as a C_min of 2 to 8 mg/liter. Therapy was empirical (73.3%) or targeted (26.7%). Wide interindividual variability in linezolid C_min levels was recorded (0.1 to 25.2 μg/ml). Overall, 65.5% of the patients had out-of-range, 41.1% had subtherapeutic, and 24.4% had supratherapeutic trough levels. We did not find a correlation between abnormal levels and adverse events, in-hospital mortality, or overall poor outcome.

Comparison of oral antibiotic failure rates in post-Roux-en-Y gastric bypass patients versus controls

BACKGROUND

Due to the malabsorptive nature of the Roux-en-Y gastric bypass (RYGB), there is a potential for impaired absorption of oral medications. Clinical outcomes of patients who receive oral antibiotics after RYGB have not been adequately described in the literature.

OBJECTIVES

The primary objective was composite therapeutic failure. Secondary objectives included comparing failure rates between antibiotic classes and at various time points since RYGB.

SETTING

University hospital, United States.

METHODS

Patients with a history of RYGB and controls who received an eligible oral antibiotic for urinary tract infection, skin and soft tissue infection, or community acquired pneumonia between April 1, 2008, and September 30, 2015, were included via retrospective chart review. Therapeutic failure rates between groups were compared and adjusted for body mass index and infection type. Failure rates among antibiotic classes and various time points since RYGB (0-1 yr, 1-1.9 yr, and≥2 yr) were also compared.

RESULTS

A total of 58 RYGB and 128 controls met inclusion and exclusion criteria. Composite therapeutic failure occurred in the RYGB and control group in 14 (24.1%) and 20 patients (15.6%), respectively (P = .18; odds ratio, 1.8; 95% confidence interval .8-4.4). RYGB patients who received fluoroquinolones or sulfonamides had a significantly increased risk of therapeutic failure.

CONCLUSIONS

RYGB was not associated with a statistically significant increased risk of composite therapeutic failure of oral antibiotics in the treatment of urinary tract infection, skin and soft tissue infection, or community acquired pneumonia compared with patients with no history of gastrointestinal resection. Further research is warranted to understand clinical outcomes of RYGB patients who receive oral antibiotics.

Oral Contraceptives after Bariatric Surgery

OBJECTIVE

Bariatric surgery offers a highly effective mode of treatment for obese patients. Some procedures such as bypass cause an alteration in normal gastrointestinal tract with possible consequences for the uptake of orally administered drugs.

METHODS

We assessed the literature to ascertain whether the use of oral drugs and especially oral contraceptives is effective and adequate after bariatric surgery.

RESULTS

The bioavailability of drugs could be affected by the solubility and pH of the modified medium after bariatric surgery and by the loss of gastrointestinal transporters. Bariatric surgery could potentially result in a transient change in the absorption of drugs such as analgesics, antibiotics, antiarrhythmics, anticoagulants, psychotropic, and oral contraceptive drugs. Effective contraception is especially critical in the postoperative period, and implants might be representing a safe contraceptive method in women undergoing bariatric surgery.

CONCLUSION

Each drug will have to be evaluated with respect to its site of absorption and its mechanism of absorption, with special attention on parameters influencing the effectiveness of the absorption processes.

Critical role of tedizolid in the treatment of acute bacterial skin and skin structure infections

Tedizolid phosphate has high activity against the Gram-positive microorganisms mainly involved in acute bacterial skin and skin structure infections, such as strains of Staphylococcus aureus (including methicillin-resistant S. aureus strains and methicillin-sensitive S. aureus strains), Streptococcus pyogenes, Streptococcus agalactiae, the Streptococcus anginosus group, and Enterococcus faecalis, including those with some mechanism of resistance limiting the use of linezolid. The area under the curve for time 0-24 hours/minimum inhibitory concentration (MIC) pharmacodynamic ratio has shown the best correlation with the efficacy of tedizolid, versus the time above MIC ratio and the maximum drug concentration/minimum inhibitory concentration ratio. Administration of this antibiotic for 6 days has shown its noninferiority versus administration of linezolid for 10 days in patients with skin and skin structure infections enrolled in two Phase III studies (ESTABLISH-1 and ESTABLISH-2). Tedizolid's more favorable safety profile and dosage regimen, which allow once-daily administration, versus linezolid, position it as a good therapeutic alternative. However, whether or not the greater economic cost associated with this antibiotic is offset by its shorter treatment duration and possibility of oral administration in routine clinical practice has yet to be clarified.

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.

Weight-based dosing in medication use: what should we know?

BACKGROUND

Weight-based dosing strategy is still challenging due to poor awareness and adherence. It is necessary to let clinicians know of the latest developments in this respect and the correct circumstances in which weight-based dosing is of clinical relevance.

METHODS

A literature search was conducted using PubMed.

RESULTS

Clinical indications, physiological factors, and types of medication may determine the applicability of weight-based dosing. In some cases, the weight effect may be minimal or the proper dosage can only be determined when weight is combined with other factors. Medications within similar therapeutic or structural class (eg, anticoagulants, antitumor necrosis factor medications, P2Y12-receptor antagonists, and anti-epidermal growth factor receptor antibodies) may exhibit differences in requirements on weight-based dosing. In some cases, weight-based dosing is superior to currently recommended fixed-dose regimen in adult patients (eg, hydrocortisone, vancomycin, linezolid, and aprotinin). On the contrary, fixed dosing is noninferior to or even better than currently recommended weight-based regimen in adult patients in some cases (eg, cyclosporine microemulsion, recombinant activated Factor VII, and epoetin α). Ideal body-weight-based dosing may be superior to the currently recommended total body-weight-based regimen (eg, atracurium and rocuronium). For dosing in pediatrics, whether weight-based dosing is better than body surface-area-based dosing is dependent on the particular medication (eg, methotrexate, prednisone, prednisolone, zidovudine, didanosine, growth hormone, and 13-cis-retinoic acid). Age-based dosing strategy is better than weight-based dosing in some cases (eg, intravenous busulfan and dalteparin). Dosing guided by pharmacogenetic testing did not show pharmacoeconomic advantage over weight-adjusted dosing of 6-mercaptopurine. The common viewpoint (ie, pediatric patients should be dosed on the basis of body weight) is not always correct. Effective weight-based dosing interventions include standardization of weight estimation, documentation and dosing determination, dosing chart, dosing protocol, order set, pharmacist participation, technological information, and educational measures.

CONCLUSION

Although dosing methods are specified in prescribing information for each drug and there are no principal pros and cons to be elaborated, this review of weight-based dosing strategy will enrich the knowledge of medication administration from the perspectives of safety, efficacy, and pharmacoeconomics, and will also provide research opportunities in clinical practice. Clinicians should be familiar with dosage and administration of the medication to be prescribed as well as the latest developments.

Treatment of community-acquired pneumonia

Community-acquired pneumonia is the sixth leading cause of death in the USA. Adherence to the 2007 Infectious Diseases Society of America/American Thoracic Society community-acquired pneumonia guidelines has been associated with improved clinical outcomes. However, choice between guideline-recommended treatments is at the discretion of the prescribing clinician. This review is intended to discuss the characteristics of these treatment options including dosing frequency, dose adjustment for renal/hepatic dysfunction, serious/common adverse events, drug interactions, lung penetration, pharmacokinetic-pharmacodynamic target and effect of obesity to help guide antimicrobial selection. An increasing portion of patients are receiving expanded empiric coverage for methicillin-resistant Staphylococcus aureus as recommended by the American Thoracic Society and Infectious Diseases Society of America for healthcare-associated pneumonia. However, this expanded coverage may not be achieving the desired improvements in clinical outcomes. We expect this increasingly diverse spectrum of patients with pneumonia to eventually result in the merger of these two guidelines to include all patients with pneumonia.

Effect of Modified Roux-en-Y Gastric Bypass Surgery on GLP-1, GIP in Patients with Type 2 Diabetes Mellitus

The type 2 diabetes mellitus (T2DM) is one of the most serious diseases that threaten public health. Modified gastric bypass surgery has been applied to the treatment of T2DM patients in the 1990s, but the therapeutic mechanism to this function is still unclear. The aim of this study was to further clarify the effect and the mechanism of modified gastric bypass surgery on glucose metabolism in patients with T2DM. In the study, the incretin indexes and blood glucose indexes were analyzed before surgery and 1 week and 1, 3, and 6 months after surgery. The results suggested that modified Roux-en-Y gastric bypass can promote GLP-1 secretion in patients with T2DM, while reducing the secretion of GIP. Thus it could effectively control blood glucose of patients with T2DM.

Comparison of different gastric bypass procedures in gastric carcinoma patients with type 2 diabetes mellitus

AIM: To determine the effect of different Roux-en-Y gastric bypass procedures in gastric carcinoma patients with type 2 diabetes mellitus.

METHODS: A retrospective analysis of the clinical data of 54 patients with gastric cancer and type 2 diabetes mellitus treated in the Department of General Surgery from January 2006 to June 2013 was conducted. The patients underwent gastrectomy using different Roux-en-Y gastric bypass procedures (traditional, n = 26; modified, n = 28). Fasting plasma glucose (FPG), two hour postprandial blood glucose (2 h PBG) and hemoglobin A1c (HbA1c) were analyzed before surgery (0 mo) and 1, 3 and 6 mo after surgery.

RESULTS: FPG and 2 h PBG levels were significantly decreased 1 mo after surgery in the traditional Roux-en-Y gastric bypass group (FPG 7.5 ± 1.3 vs 10.7 ± 1.2, P < 0.05) (2 h PBG 10.2 ± 1.8 vs 13.8 ± 3.2, P < 0.05). FPG and 2 h PBG levels were significantly decreased after surgery in the modified Roux-en-Y gastric bypass group (FPG 6.9 ± 1.2 vs 10.5 ± 1.1, 6.5 ± 1.3 vs 10.5 ± 1.1, 6.4 ± 1.2 vs 10.5 ± 1.1, P < 0.05) (2 h PBG 9.9 ± 2.2 vs 14.1 ± 2.9, 9.2 ± 2.4 vs 14.1 ± 2.9, 8.9 ± 2.6 vs 14.1 ± 2.9, P < 0.05). Compared with the levels before surgery, HbA1c levels were significantly decreased 3 and 6 mo after surgery (7.2 ± 1.1 vs 10.5 ± 1.1, 5.5 ± 1.1 vs 10.5 ± 1.1, P < 0.05). Significant differences between the two groups regarding FPG, 2 h PBG and HbA1c concentration were observed 3 and 6 mo after surgery (FPG 10.1 ± 1.5 vs 6.5 ± 1.3, 10.3 ± 1.4 vs 6.4 ± 1.2, P < 0.05) (2 h PBG 13.1 ± 2.8 vs 9.2 ± 2.4, 13.6 ± 3.1 vs 8.9 ± 2.6, P < 0.05) (HbA1c 10.1 ± 1.4 vs 7.2 ± 1.1, 10.5 ± 1.3 vs 5.5 ± 1.1, P < 0.05).

CONCLUSION: Modified Roux-en-Y gastric bypass can improve glucose metabolism in type 2 diabetic patients with gastric cancer.

Clinicians' prescribing practices for bariatric surgery patients: is there an issue?

WHAT IS KNOWN AND OBJECTIVES

Patients undergoing Roux-en-Y gastric bariatric (RYGB) surgery present a reduced absorption site, and special attention should therefore be taken when prescribing oral-dosage forms. This study was carried out to investigate the extent to which non-bariatric clinicians are aware of this issue when prescribing medicines for this population, and what type of information is available to aid them in their decision-making.

METHODS

Two questionnaires were created, one for non-bariatric clinicians and another for their patients who had undergone RYGB surgery, to gather information about the prescription practices for this population. Additionally, a literature search of pharmacokinetic studies on bariatric patients and recommended prescription practices was carried out.

RESULTS AND DISCUSSION

Of the 62 non-bariatric clinicians surveyed, 50% believed RYGB surgery interferes with drug absorption; however, 68% still prescribed tablets as the first choice form of dosage. Young clinicians (35%) were less likely to believe that RYGB surgery could affect drug absorption than experienced clinicians (43%). The main reasons for changing dosage forms were patient complaints about efficacy or difficulty in swallowing tablets. Of the 73 patients, 43 were taking drugs in tablet form after the surgery, 24 of whom had health issues unrelated to the surgery. None of the journals read by the clinicians contained pharmacokinetics (PK) studies involving bariatric surgery patients or presented recommendations for the prescription of oral-dosage forms for this population. The literature search revealed a total of 22 drugs that had undergone PK studies in RYGB patients. Fifteen of them were reported to have decreased effects, 12 of which were administered as tablets.

WHAT IS NEW AND CONCLUSION

There is still a relative lack of clinical evidence to guide clinicians when prescribing medicines for bariatric patients. It is therefore recommended that pharmacists should have greater participation in the prescription process to advise non-bariatric clinicians and educate RYGB surgery patients to help avoid therapeutic failure.

Antibiotic therapy of pneumonia in the obese patient: dosing and delivery

Purpose of review

Obesity has been shown to be associated with antibiotic underdosing and treatment failure. This article reviews the recent literature on antibiotic dosing in obese patients with pneumonia.

Recent findings

Obesity is associated with several alterations in antibiotic pharmacokinetics and pharmacodynamics, including increases in the antibiotic volume of distribution and clearance. These alterations necessitate changes in the dosing of certain antibiotics. However, data on antibiotic dosing for pneumonia in obese patients are limited and come mainly from observational studies. Additionally, dosing recommendations are often extrapolated from healthy obese volunteers and from the studies of antibiotics given for other indications.

Summary

Recognizing obesity-related pharmacokinetic and pharmacodynamic alterations is important in treating obese patients with pneumonia. Studies that evaluate such alterations and assess the impact of antibiotic dosing and delivery on the clinical outcomes of this patient population are needed.