Improved levothyroxine pharmacokinetics after bariatric surgery

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.

Morning exercise affects the absorption of oral levothyroxine: a single center pilot study

PURPOSE

Levothyroxine (LT4) is the first-line hormone replacement therapy for hypothyroidism. Several factors which have an influence on oral LT4 absorption have been previously described; however, the influence of exercise on oral LT4 absorption has not been reported, yet. It was aimed to investigate the possible effect of morning exercise, right after LT4 ingestion, on the absorption of LT4 tablets in this study.

PATIENTS AND METHODS

Patients with primary hypothyroidism who fulfilled the inclusion criteria were offered to participate in a 6-week morning exercise programme and those who agreed to participate were enrolled in our study. Patients were required to have a walk for 30 min with a regular speed right after taking their daily LT4 treatments and start having breakfast the first hour after LT4 intake. Pre- and post-exercise TSH levels were recorded and TSH percentage change was calculated.

RESULTS

All patients had decreased TSH levels after the exercise programme. There was a significant decrease in TSH levels (p < 0.001). A significant positive correlation between TSH percentage change and daily dose of LT4 per kg of body weight was also shown.

CONCLUSIONS

This is the first study which demonstrates the significant positive effect of morning exercise on the absorption of LT4 tablets. In addition to that, it was also found that as the daily dose of LT4 increases, the percentage decrease of TSH level becomes greater.

Levothyroxine personalized treatment: is it still a dream?

Levothyroxine is a milestone in the treatment of all causes of hypothyroidism. From 19th century till today, Levothyroxine experienced a great advancement, from hypodermic injections of an extract of the thyroid gland of a sheep to novel formulations, known to circumvent malabsorption issue. However, the rate of patients on suboptimal therapy is still high. Current Guidelines are clear, daily Levothyroxine dosage should be calculated based on body weight. However, we are still far away from the possibility to administer the right dosage to the right patient, for several reasons. We retrace the history of treatment with levothyroxine, pointing out strengths and weaknesses of different formulations, with particular attention to what keeps us away from tailored therapy. In the age of digitalization, the pharmaceutical industry has been giving rising importance to Digital therapeutics, that are known to be effective in reaching target therapies. By combining current knowledge of hypothyroidism therapy with cutting-edge technology, we also hypothesized what could be the future strategies to be developed in this field.

Insight of the Biopharmaceutical Implication of Sleeve Gastrectomy on Levothyroxine Absorption in Hypothyroidism Patients

PURPOSE

The growing rate of obesity led to an increased number of bariatric surgeries (BS) as a treatment option for obesity. The gastrointestinal tract (GIT) changes following BS can impact many drugs' absorption. Levothyroxine (LT4) is a synthetic thyroxine (T4) replacement used commonly as tablets to manage hypothyroidism disorder, which is more prevalent among patients with obesity. This study aims to examine the LT4 oral tablet form therapy after sleeve gastrectomy.

MATERIALS AND METHODS

A retrospective cohort study was conducted in multi-center. The LT4 doses and TSH and T4 levels were compared before and after BS. The post-surgery readings were categorized into three periods: (one to three months), (four to six months), and (> six ) months after surgery. ANOVA test was used for analysis.

RESULTS

A total of 14374 patients who underwent BS from (1/2019 to 3/2022) were screened for eligibility, and n = 101 participants matched the inclusion criteria. The TSH and T4 were not statistically significant differences before and after surgery (P-values of 0.4864 and 0.5970, respectively). However, the doses significantly differed before and after surgery in all the follow-up time point periods (P < 0.002).

CONCLUSION

The LT4 required doses significantly reduced after sleeve gastrectomy, which can be related to the improved endogenous thyroid production in patients with obesity. However, the abnormality of the GIT induced by the sleeve gastrectomy may affect the exogenous LT4 absorption. Using liquid forms of LT4 while monitoring the thyroid function parameters can optimize the treatment after the procedure.

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

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

Levothyroxine-induced serum free thyroxine response following radioactive iodine administration in patients thyroidectomized for differentiated thyroid cancer: A randomized controlled trial

PURPOSE

Patients undergoing thyroidectomy for differentiated thyroid cancer (DTC) may require 131-radioactive iodine (RAI) administration for remnant ablation or disease treatment. After ingestion, RAI resides within the gastrointestinal tract potentially leading to mucosal damage and abnormalities in the absorption of levothyroxine (LT4). The aim of this study was to evaluate whether serum FT4 peak, induced by a LT4 challenge, changes according to the LT4 formulation (solid or liquid) in both RAI and non-RAI-treated DTC patients.

METHODS

This was a monocentric controlled clinical trial, with a parallel two-groups (1:1) randomization of sequence of LT4 formulation. Patients received 200 mcg LT4 orally administered at 08:00 h, in both solid and liquid formulation, at one-week interval, at baseline and after 1, 3, and 6 months from RAI administration. At each time-point, circulating FT4 was evaluated both before LT4 assumption as well as after 1 and 3 h. FT4 increments were evaluated as area under the curve response (AUC). Analogous protocol with the same time-intervals was followed for non-RAI patients.

RESULTS

The trial included 29 consecutive DTC patients, nineteen of whom were submitted to RAI. In RAI subjects, we observed an overall significant reduction in serum FT4 increments with the most relevant decrease at the 1-month time-point, (FT4 AUC: 4.46 ± 0.72 (M ± SD) vs 4.07 ± 0.63 in baseline vs 1-month, P = 0.001) without any difference between the two LT4 formulations. No difference in serum FT4 AUC was found in non-RAI subjects.

CONCLUSION

LT4-induced serum FT4 responses are reduced following RAI administration in thyroidectomized DTC patients.

Change in levothyroxine requirements after bariatric surgery in patients with hypothyroidism

Objectives. This study aims to evaluate the need to modify the total and weight-adjusted doses of levothyroxine after bariatric surgery, identify predictors, and assess the influence of the weight loss on the levothyroxine requirements. Methods. A retrospective study in patients with treated hypothyroidism that underwent bariatric surgery. The modification of the levothyroxine dose and its association with the weight loss and other potential predictors were evaluated at 6, 12, and 24 months post-surgery. Results. Among the 63 patients included, 82.54% needed an adjustment of levothyroxine dose during the follow-up. The total weekly dose of levothyroxine (µg) decreased post-surgery at 6 months (β= -49.1; 95%CI-93.7 to -4.5; p=0.031) and 12 months (β=-54.9; 95%CI-102 to -7.8; p=0.022), but did not significantly change at 24 months (p=0.114). The weekly weight-adjusted dose (µg/k) increased at 6 months (β=1.37; 95%CI 0.91 to 1.83; p<0.001), 12 months (β=2.05; 95%CI 1.43 to 2.67; p<0.001), and 24 months (β=2.52; 95%CI 1.74 to 3.30; p<0.001). The weight loss showed association with the weight-adjusted dose (OR=1.07; 95%CI 1.02 to 1.12; p=0.004), but not the total dose (p=0.320). Conclusions. This study shows a significant decrease in the total dose of levothyroxine requirements change after bariatric surgery during the first year of the follow-up and an increase in the weight-adjusted dose over the first two years. No predictors of modification of the total dose of levothyroxine were identified.

Thyroid Function Alteration in Obesity and the Effect of Bariatric Surgery

The most common endocrine disease in obesity is hypothyroidism and secondary endocrine alterations, including abnormal thyroid function, are frequent in obesity. It is unclear whether impaired thyroid function is the cause or the consequence of increased adiposity; furthermore, there are no clear data regarding the best way to dose levothyroxine for patients with both hypothyroidism and obesity, and the effect of bariatric surgery (BS). The aim of the present article is to review some controversial aspects of the relation between obesity and the thyroid: (1) Thyroid function in obesity and the effect of BS (2) Thyroid hormone treatment (THT) in obese patients with hypothyroidism and the effect of BS. In summary: In morbidly obese patients, TSH is moderately increased. Morbid obesity has a mild central resistance to the thyroid hormone, reversible with weight loss. In morbidly obese hypothyroid patients, following weight loss, the levothyroxine dose/kg of ideal weight did not change, albeit there was an increment in the levothyroxine dose/kg of actual weight. From a clinical practice perspective, in morbid obesity, diagnosing mild hypothyroidism is difficult, BS improves the altered thyroid function and THT can be adapted better if it is based on ideal weight.

Long-term Effect of Bariatric Surgery on the Use of Levothyroxine and Thyroid Levels

BACKGROUND

The aim of this study was to evaluate the effect of bariatric surgery on the defined daily dose of levothyroxine (DDD LT4), thyroid-stimulating hormone (TSH), and free thyroxine (fT4) in female patients with hypothyroidism until 48 months after surgery.

METHODS

A retrospective observational study of hypothyroid patients who underwent bariatric surgery. Changes in DDD LT4, TSH, and fT4 over a 48 month period after surgery were analyzed.

RESULTS

Thirty-seven patients were included: 27 Roux-en-Y gastric bypass (RYGB), 6 sleeve gastrectomy (SG), 3 adjustable gastric band, and 1 one anastomosis gastric bypass. The median DDD LT4 decreased from 125 µg at baseline to 100 µg 12 months after surgery. From 24 to 48 months after surgery, the median DDD LT4 was stable at 125 µg. Most dose adjustments occurred during the first 24 months after surgery. In the time period of 24-48 months after surgery, the dose remained stable in 73.1% of the RYGB patients and in 60.0% of the SG patients. After 48 months in the RYGB group, no significant change in TSH and fT4 levels was observed.

CONCLUSIONS

Bariatric surgery led to frequent dose adjustments during the first 2 years after surgery. However, 24-48 months after surgery in the majority of patients, the dosage remained stable. No significant change in TSH and fT4 was observed 48 months after RYGB. In the first 2 years after surgery, clinicians should frequently monitor TSH and fT4 for individual dose adjustment of levothyroxine. Thereafter, the frequency of monitoring may be decreased.

Effect of laparoscopic sleeve gastrectomy on drug pharmacokinetics

INTRODUCTION

Given its feasibility and efficacy, laparoscopic sleeve gastrectomy (LSG) has become a widely accepted bariatric surgery for patients with clinically diagnosed severe obesity. LSG induces anatomical changes and subsequent weight loss which may affect drug pharmacokinetics (PK) and consequently impact dosing regimens. This review aims to examine the effect of LSG on drug PK and identify relevant gastrointestinal physiological alterations.

AREAS COVERED

PubMed, Embase, Scopus, and the Cochrane Library were searched for articles related to drug PK and LSG from inception to July 2021. Moreover, literature concerning postoperative physiological conditions in the gastrointestinal tract, such as gastric pH, gastric emptying, and small bowel transit time, etc., which may affect the PK profile of drug products was also reviewed.

EXPERT OPINION

Although LSG is classified as having restrictive property without malabsorptive bypass, postoperative changes in gastrointestinal physiology and subsequent weight loss may also lead to increased, decreased or unaltered drug exposure levels. General monitoring on drug efficacy or safety using biomarkers is proposed. In addition, therapeutic drug monitoring for those drugs when it is applicable and available is recommended to ensure efficient drug dosing and avoid adverse effects. Further research into many individual drugs are warranted.

Evaluation of Thyroid Hormone Replacement Dosing in Morbidly Obese Hypothyroid Patients after Bariatric Surgery-Induced Weight Loss

The most frequent endocrine disease in obese patients is hypothyroidism. To date, there are no clear data regarding what happens to the dose of levothyroxine (LT4) after bariatric surgery (BS). The objective of the present study was to evaluate thyroid hormone replacement dose in morbidly obese hypothyroid patients after BS-induced weight loss. We explore the best type of measured or estimated body weight for LT4 dosing. We performed an observational study evaluating patients with morbid obesity and hypothyroidism who underwent BS. We included 48 patients (three men). In morbidly obese hypothyroid patients 12 months after BS-induced weight loss, the total LT4 dose or the LT4 dose/kg ideal body weight did not change, while there was a significant increase in LT4 dose/body surface area, LT4 dose/kg weight, LT4 dose/kg adjusted body weight, LT4 dose/kg body fat, and LT4 dose/kg lean body weight. There were no differences in LT4 dose and its variation between sleeve gastrectomy (SG) and Roux-en-Y gastric bypass (RYGB). The present study strongly suggests that LT4 dosing in obese hypothyroid patients can be individually adapted more precisely if it is based on ideal body weight.

Therapeutic Equivalence of a New Preparation of Liquid Levothyroxine with Tablets in Patients with Overt Primary Hypothyroidism

BACKGROUND

A new liquid levothyroxine (LT4) dissolved in glycerol and water has recently been developed by a Greek pharmaceutical company (Uni-Pharma, Athens, Greece).

OBJECTIVES

To evaluate the therapeutic equivalence of this new liquid LT4 preparation versus the already existing tablet formulation of the same manufacturer, in order to obtain approval by the Greek National Organization for Medicines.

METHODS

This was a prospective, randomized, cross-over phase III study. The study included 50 patients (9 men and 41 non-pregnant women, with a mean age of 42.5 ± 12.5 years), with documented overt primary hypothyroidism. All subjects were well controlled on substitution therapy with various LT4 formulations. None of the patients had known LT4 malabsorption. The patients were randomized into 2 groups (A and B). The individuals of group A initially received T4® tablets for 10 ± 2 weeks and subsequently switched to T4® drops (100 μg/mL solution) at the same dose for another 10 ± 2 weeks. In group B, the reverse procedure was followed. Total T3 (T3), free T4 (fT4), and TSH were measured in all participants at enrollment and at the end of each 10 ± 2-week trial period.

RESULTS

Out of the 50 recruited patients, 6 were lost to follow-up and 5 were excluded due to non-compliance with the study protocol. In the 39 patients who completed the study, the serum TSH levels after 10 ± 2 weeks of treatment either with T4® tablets or with T4® drops did not differ (1.759 ± 1.104 vs. 2.076 ± 1.334 mIU/L, mean ± SD).

CONCLUSIONS

In hypothyroid patients, the new liquid LT4 preparation (T4® drops) is therapeutically equivalent to the tablet form (T4® tablets).

New Formulations of Levothyroxine in the Treatment of Hypothyroidism: Trick or Treat?

Background: Levothyroxine (LT4) as a medication is used by up to 5.3% of the adult population. For optimal efficacy, the traditional tablet formulation (LT4tab) requires that patients avoid concomitant ingestion with food, drinks, and certain medications, as well as excellent patient compliance. Some comorbidities influence bioavailability of LT4 and may mandate repeated dose adjustments. Summary: New LT4 formulations (soft gel [LT4soft] and liquid [LT4liq]) containing predissolved LT4 are claimed to improve bioavailability, presumably by facilitating absorption. Thus, these formulations may well be more suitable than LT4tab for patients whose daily requirements are subjected to variations in bioavailability. Here, we review the evidence and indications for use of new LT4 formulations and highlight areas of uncertainty that are worthy of further investigation. While bioequivalence is established for LT4soft and LT4liq administered to healthy volunteers compared with LT4tab in pharmacokinetic (PK) studies, therapeutic equivalence of the new formulations seems to be different in several clinical settings. Some evidence suggests that new formulations of LT4 may mitigate against the strict requirements relating to concomitant ingestion with food, drinks, and certain medications, which apply to traditional LT4 tablets. The principal indication is in selected patients with disease fluctuations and intermittent therapies with interfering medications, where the need for frequent dose adjustments and office visits may be diminished. Whether the use of LT4soft or LT4liq in patients with impaired gastric acid secretion results in better control of hypothyroidism than LT4tab remains unclear. Conclusions: The evidence in favor of using LT4soft and LT4liq in clinical practice over LT4tab is weak, and the underlying putative PK mechanisms unclear. Additional studies to investigate these potential benefits, define the cost-effectiveness, and understand the PK mechanisms involved with new LT4 formulations are needed.

Thyroid surgery in obese patients: A review of the literature

The incidence of obesity in the general population has tripled in the past four decades. The number of bariatric surgeries performed annually has quadrupled in the past ten years due to this obesity epidemic. Concomitantly, the number of patients who are obese or who have undergone bariatric surgery and have become candidates for thyroid surgery has also increased considerably. Among patients undergoing thyroidectomy in the French population, the proportion of obese patients currently represents 10 to 20%. In addition, the frequency of benign and malignant thyroid pathologies seems to be increased by obesity, with a Hazard Ratio of around 1.8 for thyroid cancers in obese women. While obesity does not seem to influence the specific post-operative morbidity of thyroidectomy, a history of malabsorptive bariatric surgery should encourage the greatest caution in patients who need to undergo thyroid surgery since it is associated with a significant risk of severe hypocalcemia (>60% in some studies) requiring intravenous calcium supplementation in about 20% of cases. In the latter situation, peri-operative vitamin D-calcium supplementation is essential. In addition, the replacement dose of Levothyroxine (T4) intended for replacement must also be adapted in obese patients, calculated not from the actual weight but from the ideal weight. The objective of this review is to discuss the influence of obesity on the evolution of nodular and neoplastic thyroid pathologies, on the morbidity of thyroid surgery as well as on post-operative drug treatments. The impact of bariatric surgery on these different aspects is also discussed.

Outcome of bariatric surgery on hypothyroidism: experience from a tertiary care center in India

BACKGROUND

Hypothyroidism is frequently found to be associated with morbid obesity. Effect of bariatric surgery on type 2 diabetes, hypertension, and sleep apnea has been studied extensively but there is a dearth of literature on its impact on thyroid function. We had published our experience of laparoscopic sleeve gastrectomy and its effect on hypothyroidism in morbidly obese patients previously. In this study, we have tried to evaluate the impact of bariatric surgery on the whole cohort of hypothyroid patients and compare the effect of various bariatric procedures on thyroid hormone replacement dose.

OBJECTIVE

To assess outcome of bariatric surgery on the hypothyroid patients and to compare the outcomes of laparoscopic sleeve gastrectomy, Roux-en-Y gastric bypass, and one-anastomosis gastric bypass in terms of reduction of thyroid hormone replacement dosage.

SETTING

Tertiary care University Hospital, India; Government Practice.

METHODS

This is a retrospective analysis of a database of all bariatric procedures done in a single unit at a tertiary care teaching hospital in India. Morbidly obese patients with hypothyroidism on thyroxine replacement were identified and their preoperative and postoperative thyroid hormone replacement dosage (THR) and thyroid stimulating hormone levels were compared.

RESULTS

Of 883 patients undergoing bariatric surgery, 180 patients were hypothyroid (on thyroxine replacement). Ninety-three patients were included in the final analysis. The mean age of the study population was 42.2 ± 10.4 years and the mean preoperative body mass index was 47.8 ± 8.3 kg/m². Mean follow-up duration was 29.8 ± 19.6 months. The excess weight loss was 58.9%. Fifty-two (55.8%) patients had a decrease in the in THR dosage, 37 (39.8%) had no change in THR dosage, and 4 patients required an increase in THR dosage. Decrease of THR dose was observed in 61.7% patients in laparoscopic sleeve gastrectomy in comparison to 45.4% in bypass group.

CONCLUSION

Bariatric surgery might cause reduction of thyroid replacement dosage in hypothyroid, morbidly obese patients.

Clinical Practice Guidelines for the Perioperative Nutrition, Metabolic, and Nonsurgical Support of Patients Undergoing Bariatric Procedures - 2019 Update: Cosponsored by American Association of Clinical Endocrinologists/American College of Endocrinology, The Obesity Society, American Society for Metabolic and Bariatric Surgery, Obesity Medicine Association, and American Society of Anesthesiologists

OBJECTIVE

The development of these updated clinical practice guidelines (CPGs) was commissioned by the American Association of Clinical Endocrinologists (AACE), The Obesity Society (TOS), American Society for Metabolic and Bariatric Surgery (ASMBS), Obesity Medicine Association (OMA), and American Society of Anesthesiologists (ASA) Boards of Directors in adherence with the AACE 2017 protocol for standardized production of CPGs, algorithms, and checklists.

METHODS

Each recommendation was evaluated and updated based on new evidence from 2013 to the present and subjective factors provided by experts.

RESULTS

New or updated topics in this CPG include: contextualization in an adiposity-based chronic disease complications-centric model, nuance-based and algorithm/checklist-assisted clinical decision-making about procedure selection, novel bariatric procedures, enhanced recovery after bariatric surgery protocols, and logistical concerns (including cost factors) in the current health care arena. There are 85 numbered recommendations that have updated supporting evidence, of which 61 are revised and 12 are new. Noting that there can be multiple recommendation statements within a single numbered recommendation, there are 31 (13%) Grade A, 42 (17%) Grade B, 72 (29%) Grade C, and 101 (41%) Grade D recommendations. There are 858 citations, of which 81 (9.4%) are evidence level (EL) 1 (highest), 562 (65.5%) are EL 2, 72 (8.4%) are EL 3, and 143 (16.7%) are EL 4 (lowest).

CONCLUSIONS

Bariatric procedures remain a safe and effective intervention for higher-risk patients with obesity. Clinical decision-making should be evidence based within the context of a chronic disease. A team approach to perioperative care is mandatory, with special attention to nutritional and metabolic issues.

Differences in Calcium Metabolism and Thyroid Physiology After Sleeve Gastrectomy and Roux-En-Y Gastric Bypass

INTRODUCTION

Bariatric surgery may modulate the hormones and elements which maintain thyroid and calcium homeostasis. These adaptations in hormonal and elemental aspects have previously been determined via some studies with variations in their findings. Thyroid volume and 24-h urinary calcium are two parameters which have not been investigated regarding whether they change during the bariatric postsurgical period. This study planned to examine the changes in calcium metabolism and thyroid gland functioning after sleeve gastrectomy (SG) and Roux-en-Y gastric bypass (RYGB).

MATERIALS AND METHODS

Seventy-three morbidly obese patients with planned bariatric surgery were enrolled in the study. Before and 12 months after the operation, parathormone (PTH), 25-OH-vitamin D3(25vitD3), TSH, free triiodothyronine (fT3), free thyroxine (fT4), calcium (Ca), 24-h urinary Ca and ultrasonography-guided thyroid volume were measured.

RESULTS

In the beginning, 73 patients were examined and 12 months after surgery out of 25 patients continuing follow-up, 20 (80%) had undergone sleeve gastrectomy (SG) while five (20%) had undergone Roux-en-Y gastric bypass (RYGB). Accompanied by significant BMI decrease, 24-h urinary Ca and thyroid volume did not significantly increase in RYGB, SG, and the whole group after 12 months. The SG group showed a significant drop in TSH (p 0.03) level, while the RYGB group showed significant decreases in fT4 (p 0.00) and fT3 (p 0.00); and significant fT3 decrease (p 0.01) was recorded for the whole group.

CONCLUSION

Bariatric surgery may modify Ca homeostasis and thyroid gland functional status. We documented that these were not statistically significant increases in 24-h urinary Ca level and thyroid volume after 1 year. Further studies are needed to understand the issue, enrolling more patients who underwent the same bariatric procedure and after accounting for the inhibition of supplementary vitamin and mineral effects.

Clinical practice guidelines for the perioperative nutrition, metabolic, and nonsurgical support of patients undergoing bariatric procedures - 2019 update: cosponsored by American Association of Clinical Endocrinologists/American College of Endocrinology, The Obesity Society, American Society for Metabolic & Bariatric Surgery, Obesity Medicine Association, and American Society of Anesthesiologists

OBJECTIVE

The development of these updated clinical practice guidelines (CPG) was commissioned by the American Association of Clinical Endocrinologists, The Obesity Society, the American Society of Metabolic and Bariatric Surgery, the Obesity Medicine Association, and the American Society of Anesthesiologists boards of directors in adherence to the American Association of Clinical Endocrinologists 2017 protocol for standardized production of CPG, algorithms, and checklists.

METHODS

Each recommendation was evaluated and updated based on new evidence from 2013 to the present and subjective factors provided by experts.

RESULTS

New or updated topics in this CPG include contextualization in an adiposity-based, chronic disease complications-centric model, nuance-based, and algorithm/checklist-assisted clinical decision-making about procedure selection, novel bariatric procedures, enhanced recovery after bariatric surgery protocols, and logistical concerns (including cost factors) in the current healthcare arena. There are 85 numbered recommendations that have updated supporting evidence, of which 61 are revised and 12 are new. Noting that there can be multiple recommendation statements within a single numbered recommendation, there are 31 (13%) Grade A, 42 (17%) Grade B, 72 (29%) Grade C, and 101 (41%) Grade D recommendations. There are 858 citations, of which 81 (9.4%) are evidence level (EL) 1 (highest), 562 (65.5%) are EL 2, 72 (8.4%) are EL 3, and 143 (16.7%) are EL 4 (lowest).

CONCLUSIONS

Bariatric procedures remain a safe and effective intervention for higher-risk patients with obesity. Clinical decision-making should be evidence-based within the context of a chronic disease. A team approach to perioperative care is mandatory with special attention to nutritional and metabolic issues.

The Effect of the Bariatric Surgery Type on the Levothyroxine Dose of Morbidly Obese Hypothyroid Patients

BACKGROUND

Doubts exist about the effect of different bariatric surgery (BS) types on levothyroxine (Lt4) absorption. We compared Lt4 doses and their variation (ΔLt4) in patients with hypothyroidism that underwent malabsorptive (MS) or restrictive (RS) surgery and studied predictors of Lt4 dose change.

METHODS

Retrospective study of morbidly obese hypothyroid patients submitted to BS. We compared RS ("sleeve" gastrectomy or adjustable gastric banding) with MS (Roux-en-Y gastric bypass) patients. We built a multivariable logistic regression and a linear regression model to study predictors of Lt4 dose changes and ΔLt4, respectively.

RESULTS

Fifty-seven patients: 35 MS and 22 RS. Mean age 47 years; 7% men. Patients submitted to MS had lower BMI at 1 year than those submitted to RS. Lt4 dose remained unchanged in 61.4%, increased in 12.3%, and decreased in 26.3% of patients. Initial and 1-year Lt4 dose were not different between surgical groups. Relative Lt4 dose, but not absolute (p = 0.07), increased at 1 year (p < 0.001). Neither BS nor BMI variation were predictors of Lt4 dose variation. BMI variation was associated with relative Lt4 dose change independently of initial BMI and BS type: β (95%CI) - 0.03 (- 0.05; 0.00); p = 0.03.

CONCLUSIONS

There were no differences in Lt4 dose and its variation between restrictive and malabsorptive techniques 1 year after surgery. Malabsorptive procedures may not affect Lt4 absorption differently from restrictive ones. Bariatric surgery type was not predictive of Lt4 dose changes. BMI variation is associated with relative Lt4 dose (dose per weight) variation and its association was independent of bariatric surgery type.

Gastrointestinal Malabsorption of Thyroxine

Levothyroxine, a largely prescribed drug with a narrow therapeutic index, is often a lifelong treatment. The therapeutic efficacy of T4 may be marred by behavioral, pharmacologic, and pathologic issues acting as interfering factors. Despite a continuous search for an optimal T4 treatment, a significant number of patients fail to show a complete chemical and/or clinical response to this reference dose of T4. Gastrointestinal malabsorption of oral T4 represents an emerging cause of refractory hypothyroidism and may be more frequent than previously reputed. In this review, we examine the pharmacologic features of T4 preparations and their linkage with the intestinal absorption of the hormone. We have stressed the major biochemical and pharmacologic characteristics of T4 and its interaction with the putative transporter at the intestinal level. We have examined the interfering role of nutrients, foods, and drugs on T4 absorption at the gastric and intestinal levels. The impact of gastrointestinal disorders on T4 treatment efficacy has been also analyzed, in keeping with the site of action and the interfering mechanisms. Based on the evidence obtained from the literature, we also propose a schematic diagnostic workup for the most frequent and often hidden gastrointestinal diseases impairing T4 absorption.

Oral levothyroxine therapy postbariatric surgery: Biopharmaceutical aspects and clinical effects

BACKGROUND

Bariatric surgery can lead to changes in the oral absorption of many drugs. Levothyroxine is a narrow therapeutic drug for hypothyroidism, a common condition among patients with obesity.

OBJECTIVE

The purpose of this work was to provide a mechanistic overview of levothyroxine absorption, and to thoroughly analyze the expected effects of bariatric surgery on oral levothyroxine therapy.

METHODS

We performed a systematic review of the relevant literature reporting the effects of bariatric surgery on oral levothyroxine absorption and postoperative thyroid function. A PubMed search for relevant keywords resulted in a total of 14 articles reporting levothyroxine status before versus after bariatric surgery.

RESULTS

Different mechanisms may support opposing trends as to levothyroxine dose adjustment postsurgery. On the one hand, based on impaired drug solubility/dissolution attributable to higher gastric pH as well as reduced gastric volume, compromised levothyroxine absorption is expected. On the other hand, the great weight loss, and altered set-point of thyroid hormone homeostasis with decreased thyroid-stimulating hormone after the surgery, may result in a decreased dose requirement.

CONCLUSIONS

For patients after bariatric surgery, close monitoring of both the clinical presentation and plasma thyroid-stimulating hormone and T4 levels is strongly advised. Better understanding and awareness of the science presented in this article may help to avoid preventable complications and provide optimal patient care.

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.

Effect of Bariatric Surgery on Thyroid Function in Obese Patients: a Systematic Review and Meta-Analysis

We aimed to make a meta-analysis regarding the effect of bariatric surgery on thyroid function in obese patients. PubMed, EMBASE, CENTRAL, and four Chinese databases were searched for clinical studies. Data were pooled using Review Manager 5.3, and subgroup and sensitivity analyses were performed if necessary and feasible. As a result, 24 articles were included into meta-analysis. Bariatric surgery was associated with significant decrease in TSH, FT3, and T3 levels. However, FT4, T4, and rT3 levels were not significantly changed postoperatively. In addition, bariatric surgery had a favorable effect on overt and subclinical hypothyroid, with reduction of thyroid hormone requirements postoperatively. In conclusion, TSH, FT3, and T3 decrease are expected following bariatric surgery, as well as non-significant change of T4, FT4, and rT3 levels.

Levothyroxine Dosing Following Bariatric Surgery

BACKGROUND

Based on the mechanisms of drug absorption, increased levothyroxine requirements are expected after bariatric surgery. However, there are conflicting data on this topic. This review evaluates the effects of bariatric surgery on levothyroxine dosing.

METHODS

Data were obtained from PubMed, Scopus, and review of published bibliographies.

RESULTS

Six of 10 studies demonstrated decreased postoperative requirements. Most demonstrated correlations between weight loss and dose. Only 3 case reports and 1 case series demonstrated increased levothyroxine requirements, attributed to malabsorption.

CONCLUSIONS

The loss of both fat and lean body mass may counteract malabsorptive effects from surgery, resulting in decreased postoperative levothyroxine requirements. In addition, the reversal of impaired levothyroxine pharmacokinetics and an altered set point of thyroid hormone homeostasis may also contribute to postoperative levothyroxine reductions.

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.

Comparative study of outcomes following laparoscopic Roux-en-Y gastric bypass and sleeve gastrectomy in morbidly obese patients: A case control study

AIM

To compare the impact of laparoscopic Roux-en-Y gastric bypass (LRYGB) and laparoscopic sleeve gastrectomy (LSG) on weight loss and obesity related comorbidities over two year follow-up via case control study design.

METHODS

Forty patients undergoing LRYGB, who completed their two year follow-up were matched with 40 patients undergoing LSG for age, gender, body mass index and presence of type 2 diabetes mellitus (T2DM). Data of these patients was retrospectively reviewed to compare the outcome in terms of weight loss and improvement in comorbidities, i.e., T2DM, hypertension (HTN), obstructive sleep apnea syndrome (OSAS), hypothyroidism and gastroesophageal reflux disease (GERD).

RESULTS

Percentage excess weight loss (EWL%) was similar in LRYGB and LSG groups at one year follow-up (70.5% vs 66.5%, P = 0.36) while it was significantly greater for LRYGB group after two years as compared to LSG group (76.5% vs 67.9%, P = 0.04). The complication rate after LRYGB and LSG was similar (10% vs 7.5%, P = 0.99). The median duration of T2DM and mean number of oral hypoglycemic agents were higher in LRYGB group than LSG group (7 years vs 5 years and 2.2 vs 1.8 respectively, P < 0.05). Both LRYGB and LSG had significant but similar improvement in T2DM, HTN, OSAS and hypothyroidism. However, GERD resolved in all patients undergoing LRYGB while it resolved in only 50% cases with LSG. Eight point three percent patients developed new-onset GERD after LSG.

CONCLUSION

LRYGB has better outcomes in terms of weight loss two years after surgery as compared to LSG. The impact of LRYGB and LSG on T2DM, HTN, OSAS and hypothyroidism is similar. However, LRYGB has significant resolution of GERD as compared to LSG.

Factors Affecting Gastrointestinal Absorption of Levothyroxine: A Review

PURPOSE

Levothyroxine (LT4) is a drug with a narrow therapeutic index, applied in small amounts (micrograms), which makes interactions in the absorption phase clinically significant. The main aim of this article was to review and present the latest information on factors that affect the gastrointestinal absorption of this drug.

METHODS

Relevant data were collected by using the MEDLINE, PubMed, EMBASE, Web of Science, Science Direct, and Scopus databases with the key words levothyroxine and absorption. Searches were not limited to specific publication types, study designs, dates, or languages. The reports were highly variable in the amount of information provided regarding study design and methods. Because of the heterogeneity of studies, no statistical analysis was performed.

FINDINGS

Many gastrointestinal disorders, such as celiac disease, atrophic gastritis, lactose intolerance, and Helicobacter pylori infection, may impede the absorption of levothyroxine. During treatment of these disorders, it is necessary to monitor serum thyroid-stimulating hormone and free T4 values to reduce the risk of developing iatrogenic hyperthyroidism. Soybeans and coffee have the greatest impact on the reduction of absorption, whereas vitamin C has the ability to increase it. Conversely, the effect of dietary fiber on the absorption of LT4 is not yet fully understood; further research is needed on this topic. A decrease in the absorption of LT4 is established and clinically significant when administered concomitantly with cholestyramine, colesevelam, lanthanum, calcium carbonate, calcium citrate, calcium acetate, iron sulfate, ciprofloxacin, aluminum hydroxide, sevelamer, or proton pump inhibitors. This effect should be taken into consideration when prescribing these drugs concomitantly with LT4. The effects of Giardia lamblia infection and the influence of orlistat, polystyrene sulfonate, raloxifene, and simethicone on absorption of LT4 have been poorly documented. For bariatric surgery, sucralfate and H₂-antagonist interactions are not well founded or contradictory evidence is available regarding their existence; additional research should be conducted.

IMPLICATIONS

The majority of the interactions are clinically significant. They are based on the LT4 adsorption on interfering substances in the digestive tract, as well as a consequently reduced amount of the drug available for absorption. These interactions can be avoided by separating the administration of LT4 and the interfering substance.

Drug disposition before and after gastric bypass: fenofibrate and posaconazole

AIMS

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Weight Loss and Variation of Levothyroxine Requirements in Hypothyroid Obese Patients After Bariatric Surgery

BACKGROUND

Obesity and hypothyroidism are both common disorders within the general population. Obese hypothyroid subjects require higher doses of levothyroxine (LT4) compared with normal weight individuals. Previous studies on the effects of bariatric surgery on LT4 dose requirements in hypothyroid subjects have provided conflicting results. The aim of this study was to evaluate the LT4 requirements in a group of obese subjects with acquired hypothyroidism, before and after weight loss achieved by bariatric surgery.

METHODS

Ninety-three obese hypothyroid subjects (mean age = 48 ± 9 years; mean body mass index = 45.9 ± 5.6 kg/m(2)), were evaluated before and 28 ± 8 months after bariatric surgery. Changes in the LT4 dose, anthropometric measures, and hormone values were evaluated. In 20 patients, data of body composition, assessed by dual energy X-ray absorptiometry, were also analyzed.

RESULTS

On average, after weight loss, a significant reduction of the total dose of LT4 was documented (from 130.6 ± 48.5 to 116.2 ± 38.6 μg/day; p < 0.001). The LT4 dose had to be reduced in 47 patients, was unchanged in 34, and had to be increased in 12 patients affected by autoimmune thyroiditis. Reduction of the LT4 dose was proportional to reduction of the lean body mass.

CONCLUSIONS

The weight loss achieved with modern surgical bariatric procedures is associated with a reduction of LT4 requirements in most hypothyroid subjects, which appears to be related to a decrease of the lean body mass. Occasionally, a concurrent decline of residual thyroid function, as it occurs in autoimmune thyroiditis, can counteract this phenomenon and eventually produce an increase of LT4 needs. It is believed that during the weight loss phase that follows bariatric surgery, there is no need for preventive adjustments of the LT4 dose, but serum thyroid hormones and thyrotropin should be periodically monitored in order to detect possible variations of LT4 requirements and to allow proper corrections of the therapy.

Dietary iodine absorption is not influenced by malabsorptive bariatric surgery

BACKGROUND

Bariatric surgery is accompanied by malabsorption of protein, carbohydrates, fats, vitamins, and trace elements. Iodine is essential to the synthesis of thyroid hormones. The aim of this study was to estimate the daily iodine intake in severely obese patients before and after bariatric surgery.

METHODS

Thirty-five severely obese patients (obese group) with a BMI of 51.3 ± 8.3 kg/m(2) were studied before, 3 months, and 6 months after bariatric surgery. Eleven out of 35 patients were subjected to gastric bypass operation Roux-en-Y and 24 were subjected to a variant of biliopancreatic diversion with long limb procedure. The patients did not use any iodine supplements and no iodine antiseptics were administered during the operation. The messmates of the patients, following a similar diet (control group) with a BMI of 31.2 ± 10.7 kg/m(2), were also studied. Serum T3, T4, TSH, thyroid peroxidase antibodies, urinary iodine excretion (UIE) in a spot urine, and thyroid volume were measured in all subjects, at baseline and at 3- and 6-month follow-up in the obese group.

RESULTS

UIE at baseline was similar in obese and control group (median (min-max), 129.5 (24.9-462) vs. 138.9 (30.8-381) μg/L, ns). In the obese group, a transient increase of UIE was observed 3 months after the operation and returned to baseline levels 6-months postsurgery.

CONCLUSIONS

The UIE is not reduced after malabsorptive bariatric surgery, although all stomach, duodenum, and a substantial part of jejunum were bypassed. It appears that iodine is absorbed sufficiently along the remaining gastrointestinal tract.

Thyroid disorders and gastrointestinal and liver dysfunction: A state of the art review

Thyroid disorders commonly impact on the gastrointestinal system and may even present with gastrointestinal symptoms in isolation; for example, metastatic medullary thyroid carcinoma typically presents with diarrhoea. Delays in identifying and treating the underlying thyroid dysfunction may lead to unnecessary investigations and treatment, with ongoing morbidity, and can potentially be life-threatening. Similarly, gastrointestinal diseases can impact on thyroid function tests, and an awareness of the concept and management of non-thyroidal illness is necessary to avoid giving unnecessary thyroid therapies that could potentially exacerbate the underlying gastrointestinal disease. Dual thyroid and gastrointestinal pathologies are also common, with presentations occurring concurrently or sequentially, the latter after a variable time lag that can even extend over decades. Such an association aetiologically relates to the autoimmune background of many thyroid disorders (e.g. Graves' disease and Hashimoto's thyroiditis) and gastrointestinal disorders (e.g. coeliac disease and inflammatory bowel disease); such autoimmune conditions can sometimes occur in the context of autoimmune polyglandular syndrome. Emphasis should also be given to the gastrointestinal side effects of some of the medications used for thyroid disease (e.g. anti-thyroid drugs causing hepatotoxicity) and vice versa (e.g. interferon therapy causing autoimmune thyroid dysfunction). In this review, we discuss disorders of the thyroid-gut axis and identify the evidence base behind the management of such disorders.

Laparoscopic sleeve gastrectomy leads to reduction in thyroxine requirement in morbidly obese patients with hypothyroidism

BACKGROUND

The impact of laparoscopic sleeve gastrectomy (LSG) on various co-morbidities including type II diabetes mellitus, hypertension, and sleep apnea is well established. However, its effect on hypothyroidism has not been given due attention evidenced by the scant literature on the subject. The purpose of this report is to assess the change in thyroxine (T4) requirement in morbidly obese patients with clinical hypothyroidism after LSG.

METHODS

We conducted a retrospective review of morbidly obese patients on T4 replacement therapy for clinical hypothyroidism who underwent LSG from August 2009 to July 2012 at our institution.

RESULTS

Of the 200 patients who underwent LSG during this period, 21 (10.5 %) were on T4 replacement therapy preoperatively for clinical hypothyroidism. Two patients were lost to follow-up. The remaining 19 patients were categorized into two groups. Group 1 comprised 13 patients with decreased T4 requirements after LSG. Group 2 comprised six patients in whom the T4 dose remained unaltered. The mean change in T4 requirement in group 1 was 42.07 % (12-100 %). Group 1 patients had a significantly higher mean preoperative body mass index (48.7 vs. 43.0 kg/m(2); p = 0.03) than the group 2 patients. There was a significant correlation between the percentage excess weight loss and the percentage change in T4 requirement in group 1 (r = 0.607, p = 0.028).

CONCLUSIONS

Sleeve gastrectomy has a favorable impact on hypothyroid status as seen by a reduction in T4 requirement in the majority of morbidly obese patients with overt hypothyroidism.

Laparoscopic sleeve gastrectomy leads to reduction in thyroxine requirement in morbidly obese patients with hypothyroidism

BACKGROUND

The impact of laparoscopic sleeve gastrectomy (LSG) on various co-morbidities including type II diabetes mellitus, hypertension, and sleep apnea is well established. However, its effect on hypothyroidism has not been given due attention evidenced by the scant literature on the subject. The purpose of this report is to assess the change in thyroxine (T4) requirement in morbidly obese patients with clinical hypothyroidism after LSG.

METHODS

We conducted a retrospective review of morbidly obese patients on T4 replacement therapy for clinical hypothyroidism who underwent LSG from August 2009 to July 2012 at our institution.

RESULTS

Of the 200 patients who underwent LSG during this period, 21 (10.5 %) were on T4 replacement therapy preoperatively for clinical hypothyroidism. Two patients were lost to follow-up. The remaining 19 patients were categorized into two groups. Group 1 comprised 13 patients with decreased T4 requirements after LSG. Group 2 comprised six patients in whom the T4 dose remained unaltered. The mean change in T4 requirement in group 1 was 42.07 % (12-100 %). Group 1 patients had a significantly higher mean preoperative body mass index (48.7 vs. 43.0 kg/m(2); p = 0.03) than the group 2 patients. There was a significant correlation between the percentage excess weight loss and the percentage change in T4 requirement in group 1 (r = 0.607, p = 0.028).

CONCLUSIONS

Sleeve gastrectomy has a favorable impact on hypothyroid status as seen by a reduction in T4 requirement in the majority of morbidly obese patients with overt hypothyroidism.

Drug disposition and modelling before and after gastric bypass: immediate and controlled-release metoprolol formulations

AIMS

The aim of the present study was to evaluate the disposition of metoprolol after oral administration of an immediate and controlled-release formulation before and after Roux-en-Y gastric bypass (RYGB) surgery in the same individuals and to validate a physiologically based pharmacokinetic (PBPK) model for predicting oral bioavailability following RYGB.

METHODS

A single-dose pharmacokinetic study of metoprolol tartrate 200 mg immediate release and controlled release was performed in 14 volunteers before and 6-8 months after RYGB. The observed data were compared with predicted results from the PBPK modelling and simulation of metoprolol tartrate immediate and controlled-release formulation before and after RYGB.

RESULTS

After administration of metoprolol immediate and controlled release, no statistically significant difference in the observed area under the curve (AUC(0-24 h)) was shown, although a tendency towards an increased oral exposure could be observed as the AUC(0-24 h) was 32.4% [95% confidence interval (CI) 1.36, 63.5] and 55.9% (95% CI 5.73, 106) higher following RYGB for the immediate and controlled-release formulation, respectively. This could be explained by surgery-related weight loss and a reduced presystemic biotransformation in the proximal gastrointestinal tract. The PBPK values predicted by modelling and simulation were similar to the observed data, confirming its validity.

CONCLUSIONS

The disposition of metoprolol from an immediate-release and a controlled-release formulation was not significantly altered after RYGB; there was a tendency to an increase, which was also predicted by PBPK modelling and simulation.

Guidelines for the treatment of hypothyroidism: prepared by the american thyroid association task force on thyroid hormone replacement

BACKGROUND

A number of recent advances in our understanding of thyroid physiology may shed light on why some patients feel unwell while taking levothyroxine monotherapy. The purpose of this task force was to review the goals of levothyroxine therapy, the optimal prescription of conventional levothyroxine therapy, the sources of dissatisfaction with levothyroxine therapy, the evidence on treatment alternatives, and the relevant knowledge gaps. We wished to determine whether there are sufficient new data generated by well-designed studies to provide reason to pursue such therapies and change the current standard of care. This document is intended to inform clinical decision-making on thyroid hormone replacement therapy; it is not a replacement for individualized clinical judgment.

METHODS

Task force members identified 24 questions relevant to the treatment of hypothyroidism. The clinical literature relating to each question was then reviewed. Clinical reviews were supplemented, when relevant, with related mechanistic and bench research literature reviews, performed by our team of translational scientists. Ethics reviews were provided, when relevant, by a bioethicist. The responses to questions were formatted, when possible, in the form of a formal clinical recommendation statement. When responses were not suitable for a formal clinical recommendation, a summary response statement without a formal clinical recommendation was developed. For clinical recommendations, the supporting evidence was appraised, and the strength of each clinical recommendation was assessed, using the American College of Physicians system. The final document was organized so that each topic is introduced with a question, followed by a formal clinical recommendation. Stakeholder input was received at a national meeting, with some subsequent refinement of the clinical questions addressed in the document. Consensus was achieved for all recommendations by the task force.

RESULTS

We reviewed the following therapeutic categories: (i) levothyroxine therapy, (ii) non-levothyroxine-based thyroid hormone therapies, and (iii) use of thyroid hormone analogs. The second category included thyroid extracts, synthetic combination therapy, triiodothyronine therapy, and compounded thyroid hormones.

CONCLUSIONS

We concluded that levothyroxine should remain the standard of care for treating hypothyroidism. We found no consistently strong evidence for the superiority of alternative preparations (e.g., levothyroxine-liothyronine combination therapy, or thyroid extract therapy, or others) over monotherapy with levothyroxine, in improving health outcomes. Some examples of future research needs include the development of superior biomarkers of euthyroidism to supplement thyrotropin measurements, mechanistic research on serum triiodothyronine levels (including effects of age and disease status, relationship with tissue concentrations, as well as potential therapeutic targeting), and long-term outcome clinical trials testing combination therapy or thyroid extracts (including subgroup effects). Additional research is also needed to develop thyroid hormone analogs with a favorable benefit to risk profile.

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.

2013 ETA Guideline: Management of Subclinical Hypothyroidism

Subclinical hypothyroidism (SCH) should be considered in two categories according to the elevation in serum thyroid-stimulating hormone (TSH) level: mildly increased TSH levels (4.0-10.0 mU/l) and more severely increased TSH value (>10 mU/l). An initially raised serum TSH, with FT4 within reference range, should be investigated with a repeat measurement of both serum TSH and FT4, along with thyroid peroxidase antibodies, preferably after a 2- to 3-month interval. Even in the absence of symptoms, replacement therapy with L-thyroxine is recommended for younger patients (<65-70 years) with serum TSH >10 mU/l. In younger SCH patients (serum TSH <10 mU/l) with symptoms suggestive of hypothyroidism, a trial of L-thyroxine replacement therapy should be considered. For such patients who have been started on L-thyroxine for symptoms attributed to SCH, response to treatment should be reviewed 3 or 4 months after a serum TSH within reference range is reached. If there is no improvement in symptoms, L-thyroxine therapy should generally be stopped. Age-specific local reference ranges for serum TSH should be considered in order to establish a diagnosis of SCH in older people. The oldest old subjects (>80-85 years) with elevated serum TSH ≤10 mU/l should be carefully followed with a wait-and-see strategy, generally avoiding hormonal treatment. If the decision is to treat SCH, then oral L-thyroxine, administered daily, is the treatment of choice. The serum TSH should be re-checked 2 months after starting L-thyroxine therapy, and dosage adjustments made accordingly. The aim for most adults should be to reach a stable serum TSH in the lower half of the reference range (0.4-2.5 mU/l). Once patients with SCH are commenced on L-thyroxine treatment, then serum TSH should be monitored at least annually thereafter.

When thyroid hormone replacement is ineffective?

PURPOSE OF REVIEW

In this article, we will consider the failure of thyroid hormone replacement therapy to normalize serum thyroid stimulating hormone concentrations. We will review circumstances and causes for failures, discuss pertinent unpublished personal cases of didactical value, and provide practical suggestions for providers encountering patients with similar presentations.

RECENT FINDINGS

Recent data are available on the benefit of novel formulations of levothyroxine therapy on malabsorption.

SUMMARY

Most frequently, reasons for ineffectiveness are noncompliance, inappropriate administration of levothyroxine, gastrointestinal disorders, and drug interactions. The diagnostic work-up should include careful history to elucidate the potential reasons for the ineffective therapy.