Influence of Bariatric Surgery on Levetiracetam Clinical Effectiveness: Case Series

Varying Lamotrigine Concentrations in Patients Following One Anastomosis Gastric Bypass Surgery: A Case Series

Objectives: Bariatric surgery, the most effective treatment for obesity and type 2 diabetes, may alter the absorption and overall bioavailability of orally administered drugs. In this case series, we present three patients undergoing one-anastomosis gastric bypass (OAGB) and their treatment with the anticonvulsant and mood stabilizer lamotrigine. Key Findings: Various mechanisms may be involved in the changes in lamotrigine blood levels following OAGB; some may lead to increased drug exposure, while others to its decrease. It was found that low and insufficient (case 1), higher (case 3), or unchanged (case 2) lamotrigine plasma levels are all possible after the surgery. Conclusion: This case series shows the complexity of drug treatment after bariatric surgery. The potentially large variability among patients in the effect of the surgery on the bioavailability of lamotrigine, a highly prescribed, life-saving medication, highlights the special care that must be taken with post-bariatric pharmacotherapy in general, and epilepsy treatment in particular.

Pharmacokinetics after bariatric surgery: adverse effects and drug safety issues in bariatric patients

INTRODUCTION

Medication management after bariatric surgery is a major and complex challenge. The altered gastrointestinal anatomy/physiology post-surgery may impact oral drug absorption/pharmacokinetics, with potential clinical implications. Along with multiple studies/cases of impaired post-surgery drug absorption/pharmacokinetics, leading to potential treatment failure, reports of increased drug exposure, leading to post-bariatric safety issues and adverse effects risk, are also available; yet, this second scenario of increased post-surgery drug levels, is less familiar in practice.

AREAS COVERED

In this article, we highlight and overview the literature reports of increased post-bariatric drug exposure and safety issues, and discuss the underlying relevant mechanisms. Finally, we provide clinical recommendations for managing this therapeutic challenge.

EXPERT OPINION

Around 25 drugs were found to exhibit post-bariatric enhanced pharmacokinetics and risk of adverse effects. Among them, toxicity with lithium treatment is well-established. Clear safety concerns were also raised for other drugs, including levothyroxine, atorvastatin, paracetamol and, importantly, immediate-release morphine. Cautious use, while closely monitoring clinical signs of toxicity, is advised for these drugs. Realizing the potentially altered post-bariatric pharmacokinetics of various drugs, and, in particular, the risk of increased exposure with related adverse effects, is essential for providing optimal pharmacological therapy and overall patient care to the growing bariatric population.

Erectile Dysfunction Therapy of Bariatric Patients: Tadalafil Biopharmaceutics and Pharmacokinetics Before vs. After Gastric Sleeve/Bypass

Bariatric surgery introduces significant changes in the gastrointestinal tract, which may affect oral drug absorption/bioavailability. Here we investigate the phosphodiesterase-5 inhibitor (PDE5i) tadalafil for potentially impaired post-bariatric solubility/dissolution and absorption. Solubility was studied in vitro in different pHs, and ex vivo in gastric content aspirated from patients pre/post-surgery. Dissolution was studied in conditions mimicking pre/post-surgery stomach. Finally, the experimental data were used in physiologically-based pharmacokinetic (PBPK) model (GastroPlus®) to simulate pre- vs. post-surgery tadalafil PK. Tadalafil demonstrated low and pH-independent solubility, both in vitro and ex vivo. Tadalafil release from all drug products and under all gastric conditions was incomplete, with particularly poor dissolution (2%) of the highest dose under post-bariatric conditions. PBPK simulations revealed altered tadalafil PK after gastric bypass-but not after sleeve gastrectomy-compared to unoperated individuals, with 44-48% decreased Cmax, 35-56% decreased AUC and 44% shorter Tmax. This mechanistic analysis suggests that tadalafil may be as effective after sleeve gastrectomy as before the procedure; meanwhile, results after gastric bypass raise concerns regarding the bioperformance of the drug. In addition, the drug's duration of action may be much shorter after gastric bypass. Thus, the effectiveness of tadalafil, widely regarded as the 'weekend pill', may be shorter than expected among gastric bypass patients.

The Complexity of Bariatric Patient's Pharmacotherapy: Sildenafil Biopharmaceutics and Pharmacokinetics before vs. after Gastric Sleeve/Bypass

Postbariatric altered gastrointestinal (GI) anatomy/physiology may significantly harm oral drug absorption and overall bioavailability. In this work, sildenafil, the first phosphodiesterase-5 (PDE5) inhibitor, was investigated for impaired postbariatric solubility/dissolution and absorption; this research question is of particular relevance since erectile dysfunction (ED) is associated with higher body mass index (BMI). Sildenafil solubility was determined both in vitro and ex vivo, using pre- vs. postsurgery gastric contents aspirated from patients. Dissolution tests were done in conditions mimicking the stomach before surgery, after sleeve gastrectomy (post-SG, pH 5), and after one anastomosis gastric bypass (post-OAGB, pH 7). Finally, these data were included in physiologically based pharmacokinetic (PBPK) modelling (GastroPlus®) to simulate sildenafil PK before vs. after surgery. pH-dependent solubility was demonstrated with low solubility (0.3 mg/mL) at pH 7 vs. high solubility at pH 1-5, which was also confirmed ex vivo with much lower solubility values in postbariatric gastric samples. Hampered dissolution of all sildenafil doses was obtained under post-OAGB conditions compared with complete (100%) dissolution under both presurgery and post-SG conditions. PBPK simulations revealed delayed sildenafil absorption in postbariatric patients (increased tmax) and reduced Cmax, especially in post-OAGB patients, relative to a presurgery state. Hence, the effect of bariatric surgery on sildenafil PK is unpredictable and may depend on the specific bariatric procedure. This mechanistically based analysis suggests a potentially undesirable delayed onset of action of sildenafil following gastric bypass surgery.

Selective COX-2 inhibitors after bariatric surgery: Celecoxib, etoricoxib and etodolac post-bariatric solubility/dissolution and pharmacokinetics

Anatomical/physiological gastrointestinal changes after bariatric surgery may influence the fate of orally administered drugs.Since non-selective NSAIDs are not well-tolerated post-surgery, selective cyclooxygenase-2 (COX-2) inhibitors may be important for these patients. In this work we investigated celecoxib, etoricoxib and etodolac, for impaired post-bariatric solubility/dissolution and absorption. Solubility was studied in-vitro, and ex-vivoin aspirated gastric contents from patients pre- vs. post-surgery. Dissolution was studied in conditions simulating pre- vs. post-surgery stomach. Finally, the experimental solubility data were used in physiologically-based biopharmaceutics model (PBBM) (GastroPlus®) to simulate pre- vs. post-surgery celecoxib/etoricoxib/etodolac pharmacokinetic (PK) profiles.For etoricoxib and etodolac (but not celecoxib), pH-dependent solubility was demonstrated: etoricoxib solubility decreased ∼1000-fold, and etodolac solubility increased 120-fold, as pH increased from 1 to 7, which was also confirmed ex-vivo. Hampered etoricoxib dissolution and improved etodolac dissolution post-surgery was revealed. Tablet crushing, clinically recommended after surgery, failed to improve post-bariatric dissolution. PBBM simulations revealed significantly impaired etoricoxib absorption post-surgery across all conditions; for instance, 79% lower Cmax and 53% decreased AUC was simulated post-gastric bypass procedure, after single 120 mg dose. Celecoxib and etodolac maintained unaffected absorption after bariatric surgery.This mechanistically-based analysis suggests to prefer the acidic drug etodolac or the neutral celecoxib as selective COX-2 inhibitors, over the basic drug etoricoxib, after bariatric surgery.