Medication Use Patterns after Gastric Bypass Surgery for Weight Management

Evaluation of An Inpatient Pharmacy Consult on Discharge Medications in Bariatric Surgery Patients

PURPOSE

To evaluate the impact of an inpatient pharmacy consult on discharge medications following bariatric surgery.

METHODS

A pharmacy consult for discharge medication review for bariatric surgery patients was instituted at an academic medical center. The intervention included conducting a medication history, reviewing home medications for updates post-bariatric surgery, creating and documenting a discharge medication plan, and providing patient education. The impact of the intervention was evaluated by comparing medication classes, doses, and formulations prescribed during the intervention relative to a historical control group.

RESULTS

The study included 85 patients who received pharmacist intervention and 167 patients who did not receive pharmacist intervention following bariatric surgery. The prescription of an extended-release medication at discharge in the intervention group was reduced by 19.3% (28.7% vs. 9.4%, p = 0.0005). For patients on hypertension medications, 94.0% had their regimen reduced in the intervention group compared with 37.5% of patients in the control group (p < 0.001). Of patients on insulin at baseline, 87.5% of patients in the intervention group had dose reductions at discharge vs. 66.7% of patients in the control group (p = 0.37). No patients in the intervention group were discharged with oral antihyperglycemic medications or non-insulin injectable medications vs. 33.3% (p = 0.12) and 20.0% (p = 0.47), respectively, in the control group. Readmission rates at 30 days were insignificantly lower in the intervention group (3.5% vs. 4.2%, p = 1).

CONCLUSIONS

Clinical pharmacist involvement in the discharge medication reconciliation process for bariatric surgery patients reduced prescribing of unadjusted medication classes, doses, and drug formulations.

Effect of Roux-en-Y gastric bypass on the bioavailability of metoprolol from immediate and controlled release tablets: a single oral dose study before and after surgery

Objective

Roux-en-Y gastric bypass (RYGB) surgery induces major changes in the gastrointestinal tract that may alter the pharmacokinetics of orally administered drugs. Results from pharmacokinetic studies are sparse. This study aimed to investigate the effect of RYGB on the bioavailability of metoprolol from immediate release (IR) and controlled release (CR) tablets in female patient volunteers before and after surgery.

Methods

An explorative, two-phase, single oral dose pharmacokinetic study of metoprolol in female patients undergoing RYGB was carried out. The dose was administered twice in each patient, 1 month before and 6 months after surgery. After intake of either 100 mg of metoprolol IR or CR tablet serum concentration-time profiles of metoprolol were determined. The endpoint was the ratio of AUC_after/AUC_before of metoprolol.

Results

Twelve patients were included in the study (metoprolol IR: 7; metoprolol CR: 5). After intake of a metoprolol IR tablet major intraindividual and interindividual differences for area under the serum concentration versus time curve (AUC) of metoprolol before and after surgery were observed (range ratio AUC_{0-10 hours after}/AUC_{0-10 hours before}: 0.74-1.98). For metoprolol CR tablets a significant reduction in bioavailability of metoprolol was observed after surgery (range ratio AUC_{0-24 hours after}/AUC_{0-24 hours before}: 0.43-0.77).

Conclusion

RYGB may influence the bioavailability of metoprolol from an IR tablet. The magnitude of changes in bioavailability after RYGB requires close monitoring of patients using metoprolol IR tablets and dose adjustment if deemed necessary. RYGB clearly reduces the bioavailability of metoprolol from a CR tablet. After RYGB clinicians may consider to increase the dose according to clinical response.

Physiologically-Based Pharmacokinetic Model on the Oral Drug Absorption in Roux-en-Y Gastric Bypass Bariatric Patients: Amoxicillin Tablet and Suspension

The potential of a physiologically-based pharmacokinetic (PBPK) model to predict oral amoxicillin bioavailability, by considering the physiological changes after "Roux-en-Y gastric bypass" (RYGB) surgery in bariatric patients, was evaluated. A middle-out approach for parameter estimations was undertaken using in vitro, in situ, and in vivo data. The observed versus predicted plasma concentrations and the model sensitivity of the simulated parameters of AUC_0-inf and C_max of amoxicillin (AMX) were used to confirm the reliability of the estimation. The model considers that a drug-transporter (Transp) in the initial segments of the normal intestine plays a significant role in the AMX absorption. A lower fraction absorbed (F_abs) was observed in RYGB patients (54.43% for suspension and 45.21% for tablets) compared to healthy subjects (77.48% capsule). Furthermore, the tablet formulation presented a lower dissolved fraction (F_d) and F_abs compared to the suspension formulation of AMX in RYGB patients (91.70% and 45.21% versus 99.92% and 54.43%, respectively). The AUC_0-inf and C_max were sensitive to changes in R_tintestine, Peff_AMX, and Transp for both healthy and RYGB models. Additionally, AUC_0-inf and C_max were also sensitive to changes in the t_lag parameter for tablet formulation in RYGB patients. The PBPK model showed a reduction in AMX bioavailability as a consequence of reduced intestinal length after RYGB surgery. Additionally, the difference in the predicted F_d and F_abs between suspension and tablet suggests that liquid formulations are preferable in postbariatric patients.

Mental Illness and Psychotropic Medication use Among People Assessed for Bariatric Surgery in Ontario, Canada

BACKGROUND

Studies completed outside of Canada have reported a high rate of mental illness and psychotropic medication use among bariatric surgery candidates with variable impacts on surgical and mental health outcomes. To our knowledge, there has been no published Canadian data on this issue.

METHODS

We conducted a secondary analysis of de-identified data from the Ontario Bariatric Registry for all individuals who completed both a baseline and psychological assessment between April 1, 2010, and February 9, 2015 (N = 10,698). We determined the rates of reported mental illness and psychotropic medication use overall and by fiscal year of assessment.

RESULTS

A past or present mental illness, most commonly depression, was recorded for 51 % of individuals. At baseline, 38 % were taking at least one psychotropic medication, most commonly antidepressants. Only a small proportion of the population were taking psychotropic medications known to be associated with high potential for weight gain. Although the prevalence of mental illness increased steadily from 35 % in 2010/2011 to 63 % in 2014/2015, there was no corresponding increase in reported medication use. Of those taking psychotropic medications, 13 % did not have a recorded history of mental illness.

CONCLUSIONS

Consistent with other international studies, our results indicate a high prevalence of mental illness and psychotropic medication use among people referred for bariatric surgery in Ontario, Canada. This supports that accurate screening practices, knowledge about how to manage psychotropic medication pre- and post-operatively and recognition for opportunities to change medications that may be associated with weight gain are required.

Rapid Reduction in Use of Antidiabetic Medication after Laparoscopic Sleeve Gastrectomy: The Newfoundland and Labrador Bariatric Surgery Cohort (BaSCo) Study

BACKGROUND

Patients who have undergone bariatric surgery generally need fewer medications as they experience improvement in, or even resolution of, various medical conditions, including type 2 diabetes mellitus, hypertension, and dyslipidemia. Published data on changes in medication use after laparoscopic sleeve gastrectomy, a type of bariatric surgery that is growing in popularity, are limited.

OBJECTIVE

To determine whether patients took fewer medications for management of type 2 diabetes, hypertension, and dyslipidemia after laparoscopic sleeve gastrectomy, relative to preprocedure medications.

METHODS

In this prospective, single-centre cohort study, a nurse practitioner used standard medication reconciliation and study data-extraction forms to interview adult patients who had undergone laparoscopic sleeve gastrectomy and determine their medication use and pertinent demographic data. The data were analyzed using generalized estimating equations and standard statistical software. Outcome measures included changes in the use of antidiabetic, antihypertensive, and antilipemic medications at 1, 3, and 6 months after the surgery.

RESULTS

A total of 65 patients who underwent laparoscopic sleeve gastrectomy between May 2011 and January 2014 met the study inclusion criteria. Before surgery, the 30 patients with type 2 diabetes were taking an average of 1.9 antidiabetic medications. One month after the procedure, 15 (50%) had discontinued all antidiabetic medications, with a further decline at 3 and 6 months (p < 0.001 at each time point). Among the patients who were taking antihypertensives (n = 48) and antilipemics (n = 33) before surgery, the decline in use occurred at a more modest rate, with 6 (12%) and 2 (6%), respectively, discontinuing these medication classes within 1 month, and 12 (25%) (p = 0.001) and 8 (24%) (p = 0.015) having discontinued by 6 months.

CONCLUSIONS

These findings suggest that patients with a history of type 2 diabetes mellitus, hypertension, and/or dyslipidemia who undergo laparoscopic sleeve gastrectomy are less likely to require disease-specific medications shortly after surgery.

Medication use following bariatric surgery: factors associated with early discontinuation

BACKGROUND

Medication discontinuation is a common result of bariatric surgery. The influence of individual patient characteristics and surgical outcomes on overall and specific medication discontinuation is not well understood. The purpose of the current study was to assess changes in medication use and identify individual characteristics and surgical outcomes associated with medication discontinuation among bariatric patients.

METHODS

The patients included in the current study received bariatric surgery from the Northern Colorado Surgical Associates of Fort Collins, Colorado, USA, between October 2007 and September 2010. Demographic, weight, health, and medication data from 400 patients with at least one 6- or 12-month post-operative appointment were extracted from the Bariatric Outcome Longitudinal Database. Multivariate regression analyses were used to investigate how patient factors affect total medication use over time, use of medications grouped by co-morbidity post-operatively, and use of specific medication classes post-operatively.

RESULTS

Baseline co-morbidities, particularly type 2 diabetes,male sex, and Roux-en-Y gastric bypass surgery were significantly associated with decreased total medication use following surgery.Weight loss, systemic disease, sex, baseline co-morbidities, surgical complications, and race were significantly associated with continued use of specific medications following surgery.

CONCLUSIONS

Bariatric surgery can help patients with certain characteristics discontinue medications but is not effective for all patients. Baseline health, sex, race, bariatric procedure,surgical complications, and post-operative weight loss may affect how bariatric patients' medication use changes preoperatively to post-operatively.

Evaluation of an In Silico PBPK Post-Bariatric Surgery Model through Simulating Oral Drug Bioavailability of Atorvastatin and Cyclosporine

An increasing prevalence of morbid obesity has led to dramatic increases in the number of bariatric surgeries performed. Altered gastrointestinal physiology following surgery can be associated with modified oral drug bioavailability (Foral). In the absence of clinical data, an indication of changes to Foral via systems pharmacology models would be of value in adjusting dose levels after surgery. A previously developed virtual "post-bariatric surgery" population was evaluated through mimicking clinical investigations on cyclosporine and atorvastatin after bariatric surgery. Cyclosporine simulations displayed a reduced fraction absorbed through gut wall (fa) and Foral after surgery, consistent with reported observations. Simulated atorvastatin Foral postsurgery was broadly reflective of observed data with indications of counteracting interplay between reduced fa and an increased fraction escaping gut wall metabolism (FG). Inability to fully recover observed atorvastatin exposure after biliopancreatic diversion with duodenal switch highlights the current gap regarding the knowledge of associated biological changes.CPT: Pharmacometrics & Systems Pharmacology (2013) 2, e47; doi:10.1038/psp.2013.23; advance online publication 12 June 2013.

Trends in oral drug bioavailability following bariatric surgery: examining the variable extent of impact on exposure of different drug classes

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

Changes to oral drug bioavailability have been observed post bariatric surgery. However, the magnitude and the direction of changes have not been assessed systematically to provide insights into the parameters governing the observed trends. Understanding these can help with dose adjustments.

WHAT THIS STUDY ADDS

Analysis of drug characteristics based on a biopharmaceutical classification system is not adequate to explain observed trends in altered oral drug bioavailability following bariatric surgery, although the findings suggest solubility to play an important role.

AIMS

To identify the most commonly prescribed drugs in a bariatric surgery population and to assess existing evidence regarding trends in oral drug bioavailability post bariatric surgery.

METHODS

A retrospective audit was undertaken to document commonly prescribed drugs amongst patients undergoing bariatric surgery in an NHS hospital in the UK and to assess practice for drug administration following bariatric surgery. The available literature was examined for trends relating to drug permeability and solubility with regards to the Biopharmaceutics Classification System (BCS) and main route of elimination.

RESULTS

No significant difference in the 'post/pre surgery oral drug exposure ratio' (ppR) was apparent between BCS class I to IV drugs, with regards to dose number (Do) or main route of elimination. Drugs classified as 'solubility limited' displayed an overall reduction as compared with 'freely soluble' compounds, as well as an unaltered and increased ppR.

CONCLUSION

Clinical studies establishing guidelines for commonly prescribed drugs, and the monitoring of drugs exhibiting a narrow therapeutic window or without a readily assessed clinical endpoint, are warranted. Using mechanistically based pharmacokinetic modelling for simulating the multivariate nature of changes in drug exposure may serve as a useful tool in the further understanding of postoperative trends in oral drug exposure and in developing practical clinical guidance.