Adjustments to warfarin dosing after gastric bypass and sleeve gastrectomy

Optimizing antithrombotic therapy in patients with coexisting cardiovascular and gastrointestinal disease

Balancing the safety and efficacy of antithrombotic agents in patients with gastrointestinal disorders is challenging because of the potential for interference with the absorption of antithrombotic drugs and for an increased risk of bleeding. In this Review, we address considerations for enteral antithrombotic therapy in patients with cardiovascular disease and gastrointestinal comorbidities. For those with gastrointestinal bleeding (GIB), we summarize a general scheme for risk stratification and clinical evidence on risk reduction approaches, such as limiting the use of concomitant medications that increase the risk of GIB and the potential utility of gastrointestinal protection strategies (such as proton pump inhibitors or histamine type 2 receptor antagonists). Furthermore, we summarize the best available evidence and potential gaps in our knowledge on tailoring antithrombotic therapy in patients with active or recent GIB and in those at high risk of GIB but without active or recent GIB. Finally, we review the recommendations provided by major medical societies, highlighting the crucial role of teamwork and multidisciplinary discussions to customize the antithrombotic regimen in patients with coexisting cardiovascular and gastrointestinal diseases.

Obesity, Challenges, and Weight-Loss Strategies for Patients With Ventricular Assist Devices

For adults with advanced heart failure, class II/III obesity (body mass index ≥35 kg/m2) represents major challenges, and it is even considered a contraindication for heart transplantation (HT) at many centers. This has led to growing interest in preventing and treating obesity to help patients with advanced heart failure become HT candidates. Among all weight-loss strategies, bariatric surgery (BSx) has the greatest weight loss efficacy and has shown value in enabling select patients with left ventricular assist devices (LVADs) and obesity to lose sufficient weight to access HT. Nevertheless, both BSx and antiobesity medications warrant caution in the LVAD population. In this review, the authors describe and interpret the available published reports on the impact of obesity and weight-loss strategies for patients with LVADs from general and HT candidacy standpoints. The authors also provide an overview of the journey of LVAD recipients who undergo BSx and review major aspects of perioperative protocols.

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

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

A Systematic Review of Warfarin Use in Post-Bariatric Surgery Patients: Cases Compiled From a Literature Review

OBJECTIVE

The objective of this review was to provide dosing recommendations for percentage change in weekly warfarin dose and rates of thrombotic and bleeding events in patients requiring long-term warfarin therapy after bariatric surgery.

DATA SOURCES

A comprehensive literature search of PubMed (through April 5, 2021), Cochrane Library, and Google Scholar (through April 5, 2021) databases was completed using the keywords warfarin OR vitamin k antagonist AND bariatric surgery.

STUDY SELECTION AND DATA EXTRACTION

Retrospective studies and matched-cohort studies evaluating preoperative and postoperative use of warfarin after bariatric surgery for obesity were considered. Weekly dose defined as sum of daily doses of warfarin for 7 consecutive days was a required outcome to be considered in this review. Patients were excluded from review if post-operative dosage change was not reported.

DATA SYNTHESIS

Six studies were included with a total of 160 patients who met the criteria. A decrease in average warfarin dose was seen in all studies, with the largest decrease occurring at 1 month postsurgery followed by an upward trend toward baseline about 90 days postsurgery. While thrombotic events were observed in none of the patients, there was an increased risk of bleeding in patients, particularly in those who underwent roux-en-y gastric bypass (RYGB) surgery.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

The study provides a specific warfarin dosing titration regimen, as well as embolic and bleed risk in post-bariatric surgery population.

CONCLUSIONS

Clinicians may consider lowering warfarin weekly dose by about 25% immediately postsurgery, with doses approaching closer to baseline about 90 days postsurgery.

Clinical insights into management options for recurrent type 2 diabetes and cardiovascular risk after metabolic-bariatric surgery

AIMS

Long-term clinical trials evaluating the effects of metabolic-bariatric surgery (MBS) on type 2 diabetes (T2D) demonstrate that a significant proportion of patients either fail to achieve remission or experience T2D recurrence over time. Furthermore, patients with recurrent T2D might require reinstitution of pharmacotherapy to control comorbidities (hypertension, dyslipidemia). This paper reviews therapeutic options in patients with T2D relapse.

DATA SYNTHESIS

Although presently there is no recommended pharmacological strategy, the available data support GLP-1 analogues (GLP-1a) as the most suitable option to control hyperglycemia post-MBS. Beside their efficacy in lowering glycemia and body weight while preserving lean mass, GLP-1a exert cardiovascular/renal-protection and are also safe and well tolerated in surgical patients. In addition, the s.c. route of administration of these medications circumvents the problem of changes in oral drugs bioavailability following MBS. Of note, the available data refers to liraglutide and needs to be confirmed with weekly GLP-1a agents. Information regarding the impact of MBS on the pharmacokinetics of lipid lowering and anti-hypertensive drugs is scarce and inconclusive. The findings indicate that timing from intervention is particularly important because of adaptive intestinal mechanisms.

CONCLUSIONS

The recurrence of T2D following MBS is a clinically relevant issue. GLP-1a therapy represents the best option to improve glycemic and weight control with good tolerability. Long-term clinical trials will clarify the impact of these drugs on cardiovascular outcomes. A close monitoring of MBS patients is advised to guide drug dosage adjustments and ensure the control of cardiovascular risk factors.

Oral Anticoagulant Use in Morbid Obesity and Post Bariatric Surgery: A Review

Bariatric surgery has emerged as a therapy for obesity and the associated comorbidities. Obesity has been shown to be a risk factor for atrial fibrillation as well as venous thromboembolism, both of which are conditions that warrant anticoagulation. There is significant underrepresentation of the morbidly obese population in prospective trials that evaluated direct oral anticoagulants and vitamin K antagonists in atrial fibrillation and venous thromboembolism. We aim to review all the available data that assessed these oral anticoagulants in the morbidly obese population (body mass index >40 kg/m² and weight >120 kg) and in the post-bariatric surgery population. Our findings suggest that direct oral anticoagulants may be safe and effective for anticoagulation in morbidly obese patients for both atrial fibrillation and venous thromboembolism. However, warfarin is the preferred agent in the post-bariatric surgery population, given the limited number of studies on direct oral anticoagulants in this population. Further adequately powered randomized control trials are needed to confirm the safety and efficacy of these oral anticoagulants in the morbidly obese and post-bariatric surgery population.

Thromboembolism, Bleeding, and Mortality Incidence of Direct Oral Anticoagulants Versus Warfarin Postbariatric Surgery

BACKGROUND

There is no randomized controlled trial comparing direct oral anticoagulants (DOACs) and warfarin following bariatric surgery to date. The mortality, thromboembolism, and bleeding risk of DOACs in comparison with warfarin following bariatric surgery remains unclear. We aimed to provide a clinical comparison between DOACs and warfarin for these 3 prespecified outcomes.

METHODS

A systematic literature search was performed on November 10, 2019, using PubMed, Embase, clinicaltrial.gov, and Cochrane databases. Studies with adult patients who were on either warfarin or DOACs following bariatric surgery and reported the incidence of thromboembolism, bleeding, or mortality were included. Pooled incidence for these prespecified outcomes and its 95% confidence interval (CI) were calculated for each drug separately using the random-effects model, along with a nonadjusted P value comparing the 2 subgroups.

RESULTS

A total of 11 studies (805 patients) were included. Comparing DOACs to warfarin, the following pooled incidences were observed for mortality (DOACs: 3.0%; 95% CI 0.4%-18.6% versus warfarin: 1.5%; 95% CI 0.8%-2.9%; P value comparing the 2 subgroups = .38), thromboembolism (DOACs: 4.9%; 95% CI 1%-21.1% versus warfarin: 1.5%; 95% CI 0.8%-2.9%; P value = .18), and bleeding (DOACs: 3.9%; 95% CI 0.7%-18.2% versus warfarin: 11.3%; 95% CI 5.7%-21.4%; P value = .23).

CONCLUSION

The results of our meta-analysis remain hypothesis-generating, providing rationale for future randomized controlled trial design or well-designed comparative observational studies. Currently, it does not support the change in the current recommendation from warfarin to DOACs following bariatric surgery.

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

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

Recurrent Thrombi in an Obese Patient With History of Bariatric Surgery Despite Anti-Xa Therapy

Obesity and gastric bypass surgery can complicate anticoagulation therapy. In general, patients post-bariatric surgery are considered to be at a moderate risk for deep venous thromboembolism or pulmonary embolism. 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 guidelines recommend chemical prophylaxis with unfractionated heparin or low molecular weight heparin after surgery until the patient is fully mobile, and for those who require chronic anticoagulation, the International Society of Thrombosis and Haemostasis recommend warfarin if body mass index (BMI) is above 40 kg/m² or weight is more than 120 kg. Clinical decision making regarding anticoagulation in the following patient case is complicated by multiple factors, most notably the combination of obesity and history of gastric bypass surgery. This patient failed multiple anticoagulation regimens, with apixaban and rivaroxaban therapies each ending in venous thromboemboli and warfarin leading to subtherapeutic International Normalized Ratio (INR)s despite dose adjustment. However, she is currently therapeutic on the combination of enoxaparin and warfarin as shown by INR and anti-Xa level monitoring. In this case and similar instances, there could be a need for anticoagulant dose adjustments, different INR goals, or a combination of different anticoagulants. Providers should take an individualized approach to patients who have had bariatric surgery with elevated BMI as a key factor in anticoagulant selection.

A review of indications and comorbidities in which warfarin may be the preferred oral anticoagulant

WHAT IS KNOWN AND OBJECTIVE

Direct oral anticoagulants (DOACs) are increasingly prescribed instead of warfarin for chronic anticoagulation for ease of dosing, fewer interactions, and less stringent monitoring. However, it is important to consider indications and comorbidities for which warfarin is still the preferred anticoagulant. This review aims to capture these clinical scenarios in which warfarin may still be preferred over DOACs.

METHODS

We undertook a comprehensive literature search using the PubMed database. Key search terms were based on DOAC clinical trial exclusion criteria, as well as indications and conditions in which the use of DOACs for anticoagulation has suggested harm. Society guidelines and tertiary literature were used to inform expert opinion where necessary. Studies were included if they investigated the use of DOACs or warfarin in the identified indications or conditions.

RESULTS AND DISCUSSION

Currently, evidence for the use of warfarin over DOACs for anticoagulation is strongest for patients with prosthetic valves, antiphospholipid syndrome, or a high risk of gastrointestinal bleeding. For several clinical situations, including mitral stenosis, obesity, altered gastrointestinal anatomy, pulmonary arterial hypertension, renal or hepatic impairment, and left ventricular thrombus, evidence is lacking but may eventually support the use of DOACs. Depending on indication and condition, appropriateness of DOAC use may vary by agent.

WHAT IS NEW AND CONCLUSION

New evidence continues to support new indications and conditions in which DOACs may be appropriate to use for anticoagulation. There are key clinical scenarios, however, in which emerging literature continues to support warfarin as the preferred anticoagulant.

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

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

Increased Paracetamol Bioavailability after Sleeve Gastrectomy: A Crossover Pre- vs. Post-Operative Clinical Trial

Oral drug bioavailability may be significantly altered after laparoscopic sleeve gastrectomy (LSG), the most popular bariatric procedure worldwide. Paracetamol (acetaminophen) is the post-bariatric analgesic/antipyretic drug of choice. In this work we studied and analyzed the LSG effects on systemic bioavailability and pharmacokinetics of paracetamol after oral administration of solid vs. liquid dosage form. A 4-armed, pharmacokinetic, crossover trial was performed in patients enrolled for LSG. Single paracetamol dose (500 mg), as caplet (n = 7) or syrup (n = 5), was administered before vs. 4–6 months post-LSG. Bioavailability was enhanced after LSG; in the caplet groups, average AUC_0–t increased from 9.1 to 18.6 µg·h/mL with AUC_0–t difference of 9.5 µg·h/mL (95% CI 4.6–14.5, p = 0.003). C_max increased from 1.8 (95% CI 1.2–2.5) to 4.2 µg/mL (3.6–4.8) after LSG (p = 0.032). In the syrup groups, AUC_0–t increased from 13.4 to 25.6 µg·h/mL, with AUC_0–t difference of 12.2 µg·h/mL (95% CI 0.9–23.5, p = 0.049). C_max changed from 5.4 (95% CI 2.5–8.4) to 7.8 µg/mL (6.1–9.6), and systemic bioavailability was complete (102%) after the surgery. Overall, decreased paracetamol exposure in obesity, with recovery to normal drug levels (caplet) or even higher (syrup) post-LSG, was revealed. In conclusion, attention to paracetamol effectiveness/safety in obesity, and after bariatric surgery, is prudent.