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A Review of Gastric Bypass: Implications for Pharmacotherapy and Disease State Management David G. Fuentes, PharmD BCPP CGP Assistant Professor Pacific University of Oregon School of Pharmacy Educational Outline • • • • • • • • Describing Gastric Bypass (GB) Risk factors associated with a need for GB Common system co-morbidities in patients undergoing GB Clinical evaluation and monitoring parameters before and after GB Post-GB changes in metabolism and absorption Review of the literature regarding GB Implications on drug therapy Case scenarios and concept application Gastric Bypass (GB) • Terminology – Weight loss surgery (WLS) 1, 2 – Open surgery 1 – Laparoscopy adjustable gastric banding (LAGB) 1, 5-7 – Bariatric surgery 3, 4 – Gastric banding 3 – Roux-en-Y gastric bypass (RYGB) 4, 6, 8 – Hand-assisted laparoscopic Roux-en-Y gastric bypass (HALGB) 9 Major General Approaches to GB • Adult patients: emerging increase in laparscopic adjustable banding approach 5 – Review of approx. 31,300 surgeries (2004 – 2007) • Adjustable banding: 7% 23% • Gastric bypass (GB): 53 66% • Pediatric patients: greater use of RYGB and LAGB (non-FDA approved) 6, 10 • Medication and adjustable gastric banding (AGB) 7 – Adding orlistat prescription dose The Impact of GB in the US • Increasing trends 2 – Example: Wisconsin inpatient hospital • Approx. 50 procedures (1990 – 1992) • Approx. 1880 procedures (2000 – 2002) • Health policy and financial implications 1, 3, 11 – Funding available based on conditions • Accreditation in WLS, use of multi-disciplinary care • Emerging Benefits 1, 4, 12 – Reduction in weight correlating with improvements in chronic conditions Common Co-morbid Systems in GB Patients • Systems: Cardiac, endocrine, gastrointestinal, neuro-psychiatric, fetal-reproductive, vascular • Degrees of obesity 9, 11-13 – Morbidly obese: Body mass index (BMI) > 40 kg/m2 – Super obese: BMI > 50 kg/m2 Evaluation Prior to GB • Approaching GB pre-assessment as a patientspecific process 7, 8, 14-19 – Holistic patient evaluation • Socioeconomic, access to care, age, chronic diseases, ongoing risk factors, baseline physical measures and objective data, ongoing stressors and mental health • Importance of gauging general health, cognitive and physical abilities, specific expectations and co-morbidities 8, 11, 13, 15, 17 Pharmacological Considerations after GB • Inter-patient variability is common – Lab values and deficits can clinically stabilize and improve within 2 yrs 20, 21 – Higher baseline BMI, diabetes and on multi-drug regimens experienced excessive weight loss (EWL) 21, 22 – Electrolytes may be severely affected and monitoring may be necessary 21, 23 • May complicate medication options and increase monitoring burdens Changes in Absorption after GB • Digestion and absorption of fats was reduced in patients depending on the procedure 16, 24 • Reported shift in the GI micro-flora affecting digestion and absorption 25 • General absorption is diminished greatly status-post (s/p) bariatric surgery 26, 27 • Case reports involve jejuno-ileal bypass, gastric bypass/gastroplasty and bilio-pancreatic diversion 26 Changes in Metabolism after GB • Altered medication absorption and metabolism are reported as drug-specific 26 • Altered properties affecting medications’ physical properties, pharmacokinetics and dynamics 26, 28 – Medication dissolution – Medications absorption – Handling of lipophilic agents – Enterohepatic recirculation Impact of GB on Pharmacotherapy and Disease State Management • Implicated in improvement of chronic conditions – Weight reduction, cost savings, improved chronic health conditions, and reduced all-cause mortality 1, 2, 8, 12, 29-36 – Gastro-esophageal reflux disease (GERD) 4, 37-38 – Generally improved quality of life (QOL) 38-39 – Prevention of complications associated with pregnancy 40 – Does not consistently affect conception or fetal development in a negative manner 41-43 • Negative conditions s/p GB – – – – Chronic anemia secondary to reduced intestinal absorption 44 Delayed hyperinsulinemic - hypoglycemic response after RYGB 45 Reduced GI motility after gastric banding 46 Gallstone and renal stone formation 1, 5, 6, 14, 45 Specific Implications for Drug-Therapy • Medications requiring narrow therapeutic window maintenance for safety and efficacy • Example in an RYGB patient 47 – Patient using phenytoin and previously controlled x30 years Specific Implications for Drug-Therapy • Review of medication absorption s/p GB procedure finds diminishing levels and possibly related reduced efficacy 26 – Cyclosporine – Levothyroxine – Phenytoin – Rifampin – Antibiotics Specific Implications for Drug-Therapy • Treatment of malignancy was suspected to adversely affect temozolomide levels 48 • A time for investigation – Patients exhibiting treatment failure were tested for medication levels – Concentrations were not different between GB and non-GB patients • Authors of this report and other investigations concluded that drug kinetics must be evaluated on “drug-by-drug basis” 48-50 Specific Implications for Drug-Therapy • A case report highlights possible warfarin resistance thought to be linked to recent total gastrectomy with a Roux-en-Y esophagojejunostomy procedure 51 – Previously stabilized 71-year old woman with chronic atrial fibrillation on approx. 5 mg/day – Patient underwent surgery and was bridged to outpatient afterwards to INR 2.0-3.0 – Months later she required up to 20 mg/day of warfarin for INR 2.0 – 3.0 Specific Implications for Drug-Therapy • Starting drug therapy sooner to preserve bone health and integrity? 23, 27 – Younger GB patients may be requiring more calcium supplements and vitamin D therapy – Hormonal therapy may be indicated sooner for females at risk Specific Implications for Drug-Therapy • Control of Parkinson’s disease reported 52 – Patients were controlled previously with chronic levodopa therapy – Evidence reviewed showed that having frequent “on and off” fluctuations were correlated to the pharmacokinetics related to the GI system and absorption (reduced gastric emptying) – Patients s/p GB did much better on intravenous trials of levodopa ethyl-ester injections which bypass the GI Specific Implications for Drug-Therapy • Additional supplementation and s/p GB medications 27, 42, 53-54 – Major elements considered to be missing include: calcium, vitamins A, D, E and K, multiple vitamins, iron, folate, and cyanocobalamin 53 – Ursodeoxycholic acid after GB to prevent gallstones 14, 45 – Babies born to mothers s/p GB may require monitoring and supplementation of B12 – Pregnant women should adhere to folic acid supplementation 16-17, 55 – Vitamin excess should be avoided and patient-specific needs should be targeted 56-57 Case 1 • JK is a 38 year old patient using fluoxetine, olanzapine, lithium, “as needed” zolpidem, nightly temazepam, lisinopril, metoprolol tartrate, enteric coated aspirin, “as needed” ibuprofen • He drinks alcohol when his depression is worsened. He thinks his medications are losing their efficacy due to his GB (surgery done RYGB 1.5 years ago) Case 2 • BC is a 35 year old female wanting to seek help for her depression. She has “tried it all” and is open to using anything. • She is also complaining about her chronic pain becoming worse. She has been using oxycodone 80 mg PO TID, “as needed” oxycodone/acetaminophen, gabapentin, and twice-daily cyclobenzaprine. Emerging and Difficult Issues • • • • • Procedure failure 8 Pediatrics: childhood obesity 6 Alternative surgical procedures 3, 6 Good weight loss vs. EWL 21 Lack of data specific to drug dissolution disposition in BMI > 40 kg/m2 and s/p GB 28, 49 • The impact of vitamin D depletion on HTN control 43 • Greater sensitivity to drug-induced ulceration 42 • Immediate and longitudinal follow-up 4, 6, 9 Desired Data and Information Sets • Specific information on dosing in special populations • Targets of knowledge and clinical research – Starting doses and variation in release forms/salts – Active metabolites and elimination – Chronic maintenance doses • Should the drug dose change as the disease changes? – Possible changes in adherence patterns – Educating pharmacists on signs of medication treatment failure Conclusion • Much more information and practice pearls are necessary as they pertain to medication dosing, use and efficacy after GB procedures • GB procedures are becoming extremely common in various populations • Long-term nutritional deficits will need to be investigated and effectively treated in this population Works Cited 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 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