Correction to: Longitudinal Impacts of Gastric Bypass Surgery on Pharmacodynamics and Pharmacokinetics of Statins.

In the original article the authors failed to include the following footnote.

Longitudinal Impacts of Gastric Bypass Surgery on Pharmacodynamics and Pharmacokinetics of Statins.

PURPOSE: Undergoing Roux-en-Y gastric bypass (RYGB) is expected to affect orally administered drug absorption. Statins are commonly prescribed to patients with obesity for the prevention of atherosclerotic cardiovascular diseases by lowering cholesterol. This is the first longitudinal prospective study on impacts of RYGB on weight loss, pharmacodynamics, and pharmacokinetics of atorvastatin, rosuvastatin, and simvastatin, and their active metabolites, up to 1-year post-surgery. METHODS: Forty-six patients were recruited, five patients on atorvastatin, twelve on rosuvastatin, nine on simvastatin, and twenty on no statin. The concentrations of atorvastatin, rosuvastatin, and simvastatin with their active metabolites were monitored. RESULTS: Mean plasma concentrations of atorvastatin and metabolites and rosuvastatin normalized by the unit dose [(nM)/(mg/kg)] decreased by 3- to 6-month post-surgery. Conversely, simvastatin and its metabolite concentrations increased up to 6-month post-surgery, then declined to preoperative levels by 1-year post-surgery. The metabolisms of atorvastatin to hydroxyl-metabolites and simvastatin to simvastatin acid were decreased after RYGB. The weight loss and PD outcomes were comparable between statin and non-statin groups suggesting the key impacts were from RYGB. The discontinuation or reduction of dose of atorvastatin or rosuvastatin post-RYGB exhibited rebounds of LDL levels in some subjects, but the rebound was not apparent with patients on simvastatin pre-surgery. CONCLUSION: Discontinuations of statin dosing post-RYGB require LDL monitoring and reducing the dose to half seems to have better results. Patients on statin treatment post-RYGB should be followed-up closely based on our pharmacokinetic findings, to ensure therapeutic effects of the treatment with minimal adverse effects.

Simultaneous LC-MS/MS analysis of simvastatin, atorvastatin, rosuvastatin and their active metabolites for plasma samples of obese patients underwent gastric bypass surgery.

Statins, HMG-CoA reductase inhibitors, are considered the first line treatment of hyperlipidemia to reduce the risk of atherosclerotic cardiovascular diseases. The prevalence of hyperlipidemia and the risk of atherosclerotic cardiovascular diseases are higher in obese patients. Published methods for the quantification of statins and their active metabolites did not test for matrix effect of or validate the method in hyperlipidemic plasma. A sensitive, specific, accurate, and reliable LC-MS/MS method for the simultaneous quantification of simvastatin (SMV), active metabolite of simvastatin acid (SMV-A), atorvastatin (ATV), active metabolites of 2-hydroxy atorvastatin (2-OH-ATV), 4-hydroxy atorvastatin (4-OH-ATV), and rosuvastatin (RSV) was developed and validated in plasma with low (52-103 mg/dl, <300 mg/dl) and high (352-403 mg/dl, >300 mg/dl) levels of triglyceride. The column used in this method was ACQUITY UPLC BEH C18 column (2.1 × 100 mm I.D., 1.7 µm). A gradient elution of mobile phase A (10 mM ammonium formate and 0.04% formic acid in water) and mobile phase B (acetonitrile) was used with a flow rate of 0.4 ml/min and run time of 5 min. The transitions of m/z 436.3 → 285.2 for SMV, m/z 437.2 → 303.2 for SMV-A, m/z 559.2 → 440.3 for ATV, m/z 575.4 → 440.3 for 2-OH-ATV and 4-OH-ATV, m/z 482.3 → 258.1 for RSV, and m/z 412.3 → 224.2 for fluvastatin (internal standard, IS) were determined by Selected Reaction Monitoring (SRM) method to detect transitions ions in the positive ion mode. The assay has a linear range of 0.25 (LLOQ) -100 ng/ml for all six analytes. Accuracy (87-114%), precision (3-13%), matrix effect (92-110%), and extraction recovery (88-100%) of the assay were within the 15% acceptable limit of FDA Guidelines in variations for plasma with both low and high triglyceride levels. The method was used successfully for the quantification of SMV, ATV, RSV, and their active metabolites in human plasma samples collected for an ongoing clinical pharmacokinetic and pharmacodynamic study on patients prior to and post gastric bypass surgery (GBS).

Racial disparity in short-term outcomes after gastric bypass surgery.

BACKGROUND: Roux-en-Y gastric bypass procedure is the most frequently performed bariatric surgery for the extremely obese in USA. However, the information about the effects of racial/ethnic differences, comorbidities, and medication use on weight loss outcomes is limited. The objectives of this study were to investigate if race/ethnicity, comorbidities, and medication use affect weight loss effectiveness after the surgery. METHODS: This is a retrospective observational study conducted at one teaching hospital at Houston metropolitan area, TX, USA. Patients between 18 and 64 years, with body mass index (BMI) of ≥ 40 or BMI of ≥ 35 with comorbidities, who had completed medical evaluations/consultations and met insurance policy requirements, were included in the study. RESULTS: From a total of 40 patients in the study (40 % African Americans, 35 % Caucasians, 17.5 % Hispanics, 7.5 % others), the weight loss was significantly greater in Caucasian patients at 6 months after the surgery, with mean percentage excess weight loss (%EWL) of 40.6 ± 17.3, as compared to all other racial groups combined at %EWL of 30.9 ± 11.5 (p value 0.04). No association was found between the 6-month weight loss and other variables including age, gender, BMI prior to surgery, comorbidities, and total number of medications taken before the surgery. CONCLUSIONS: This study found that Caucasian patients had a significantly greater %EWL at 6 months post-op as compared to their African-American and Hispanic counterparts. No other variables exhibited significant impact on the weight loss. Further studies with a larger sample size are needed to confirm the results from this study.

Age-related macular degeneration.

Age-related macular degeneration (AMD) is the leading cause of blindness in the elderly, and the prevalence of the disease increases exponentially with every decade after age 50 years. It is a multifactorial disease involving a complex interplay of genetic, environmental, metabolic, and functional factors. Besides smoking, hypertension, obesity, and certain dietary habits, a growing body of evidence indicates that inflammation and the immune system may play a key role in the development of the disease. AMD may progress from the early form to the intermediate form and then to the advanced form, where two subtypes exist: the nonneovascular (dry) type and the neovascular (wet) type. The results from the Age-Related Eye Disease Study have shown that for the nonneovascular type of AMD, supplementation with high-dose antioxidants (vitamin C, vitamin E, and ß-carotene) and zinc is recommended for those with the intermediate form of AMD in one or both eyes or with advanced AMD or vision loss due to AMD in one eye. As for the neovascular type of the advanced AMD, the current standard of therapy is intravitreal injections of vascular endothelial growth factor inhibitors. In addition, lifestyle and dietary modifications including improved physical activity, reduced daily sodium intake, and reduced intake of solid fats, added sugars, cholesterol, and refined grain foods are recommended. To date, no study has demonstrated that AMD can be cured or effectively prevented. Clearly, more research is needed to fully understand the pathophysiology as well as to develop prevention and treatment strategies for this devastating disease.

Warfarin resistance associated with parenteral nutrition.

Warfarin is widely used as an oral anticoagulant for the prevention and long-term treatment of venous thromboembolism and for the prevention of thromboembolic complications associated with atrial fibrillation, heart valve replacement and myocardial infarction. Warfarin exerts its anticoagulation effect by inhibiting the enzymes responsible for the cyclic interconversion of vitamin K in the liver. Vitamin K serves as a cofactor required for the carboxylation of the vitamin K-dependent coagulation proteins. By inhibiting the supply of vitamin K in the production of these proteins, warfarin indirectly slows their rate of synthesis. The authors describe a 46-year-old patient readily anticoagulated for a deep venous thrombosis who then required large doses of warfarin after initiation of total parenteral nutrition, which included lipid preparation that contained vitamin K, in addition to vitamin K required for the daily parenteral nutrition. The effect of total parenteral nutrition with vitamin K on anticoagulation is discussed.