Anticipated pharmacokinetic changes after bariatric surgery: Based on the anticipated medication and absorption changes after 3 specific procedures: 2 types of restrictive procedures (gastric banding and sleeve gastrectomy) and 1 type with both restrictive and malabsorptive properties (RYGB).
| PHARMACOKINETIC PARAMETER | POTENTIAL PHARMACOKINETIC PARAMETER CHANGES | POTENTIAL THERAPEUTIC IMPLICATIONS FOR ORAL MEDICATIONS | |
|---|---|---|---|
| RESTRICTIVE SURGERY | MALABSORPTIVE SURGERY | ||
| Gastric motility | Might be impaired6,43 | Disintegration and dissolution of oral medications might decrease6 | |
| Gastric volume | Decreased, thereby decreasing the amount of fluids in the stomach available to act as solvents6 | ||
| Gastric pH | Typically becomes more basic after bariatric surgery6,43 | Solubility of basic drugs might decrease whereas solubility of acidic drugs might increase6,43 | |
| Surface area | Sleeve gastrectomy will decrease stomach surface area6 | RYGB will decrease contact with stomach and intestinal surface areas6 | Dissolution and absorption6 of oral medications might decrease |
| Bile secretions | NA | Medications will have less contact with bile secretions6,43 | Dissolution of highly lipophilic drugs might decrease6,43 |
| Carrier proteins (eg, P-glycoprotein) | NA | Bypasses certain carrier proteins that are highly expressed in the proximal small intestine6,43 | Might either increase or decrease absorption as both influx transporters and efflux pumps are known to be expressed in the upper small intestine6,43 |
| First-pass metabolism | NA | The proximal small intestine has a high concentration of CYP3A4 enzymes6 | First-pass metabolism of CYP3A4 substrates might be decreased initially after malabsorptive procedures; decreased dosages might be required6,44,45 |
| Hepatic CYP enzyme activity might increase with weight loss44,45 | First-pass metabolism of all CYP enzyme substrates (including CYP3A4 substrates) might increase with weight loss; increased dosages might be required | ||
CYP—cytochrome, NA—not applicable, RYGB—Roux-en-Y gastric bypass.