Introduction
Obesity (body mass index (BMI) above 30 kg/m2) is currently one of the major health issues, with a worldwide prevalence of 13% 1. Individuals with (morbid) obesity are exposed to an increased risk of cardiovascular disease, cancer, diabetes mellitus, hypertension, arthritis, sleep apnea, and other co-morbidities, at higher mortality rates 2,3.
For patients with morbid obesity (BMI above 40 kg/m2) or obesity with a BMI above 35 kg/m2 with one or more comorbidities like type 2 diabetes or hypertension, modification of the gastro intestinal (GI) tract by bariatric surgery is currently the most effective long term treatment 4–7. Surgery results in weight loss up to 32 ± 8% after two years and has shown to lead to decreased incidence of diabetes, myocardial infarction, stroke, and cancer, and in a reduction in overall long-term mortality4,8,9. In addition, obesity has a negative impact on quality of life, which improves significantly after bariatric surgery10.
Common techniques used in bariatric surgery includes, the sleeve gastrectomy (SG) and Roux-en-Y gastric bypass (RYGB)11. The RYGB is associated with several anatomical and physiological changes. RYGB introduces a small gastric pouch, which results in an increased gastric pH 12,13. The gastric pouch is connected to the lower part of the intestine, bypassing the small intestine and biliary limb. During the SG procedure, a small longitudinal stomach in created. For both types of surgery, these alterations in the GI tract are known to lead to nutritional deficiencies for which standardized nutritional supplementation is commonly advised 7. Similarly, it can be anticipated that these changes may alter the absorption of drugs given orally.
Many patients who undergo bariatric surgery use one or more drugs to manage their co-morbid disease(s). Relevant drugs to these patients include cardiovascular (26%) and antidiabetic drugs (26%), analgesics (21%), anti-inflammatory and antirheumatic products (non-steroids) (10%), antidepressants (21%), thyroid therapeutics (12%) and drugs for obstructive airway disease (25%) 14.
In addition to the alterations in oral absorption due to modifications in the digestive tract there are also changes in distribution, metabolism and/or elimination of drugs as the result of substantial weight-loss associated with bariatric surgery 15,16. The purpose of this article is to provide an overview of how bariatric surgery may influence the process of oral drug absorption and to give specific dosage advice for commonly used potent drugs in this special patient population.