Carmil Azran1, Daniel Porat2, Noa Fine-Shamir2, Nirvana Hanhan2, Arik Dahan3. 1. Herzliya Medical Center, Herzliya, Israel. 2. Department of Clinical Pharmacology, School of Pharmacy, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel. 3. Department of Clinical Pharmacology, School of Pharmacy, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel. Electronic address: arikd@bgu.ac.il.
Abstract
BACKGROUND: Bariatric surgery can lead to changes in the oral absorption of many drugs. Levothyroxine is a narrow therapeutic drug for hypothyroidism, a common condition among patients with obesity. OBJECTIVE: The purpose of this work was to provide a mechanistic overview of levothyroxine absorption, and to thoroughly analyze the expected effects of bariatric surgery on oral levothyroxine therapy. METHODS: We performed a systematic review of the relevant literature reporting the effects of bariatric surgery on oral levothyroxine absorption and postoperative thyroid function. A PubMed search for relevant keywords resulted in a total of 14 articles reporting levothyroxine status before versus after bariatric surgery. RESULTS: Different mechanisms may support opposing trends as to levothyroxine dose adjustment postsurgery. On the one hand, based on impaired drug solubility/dissolution attributable to higher gastric pH as well as reduced gastric volume, compromised levothyroxine absorption is expected. On the other hand, the great weight loss, and altered set-point of thyroid hormone homeostasis with decreased thyroid-stimulating hormone after the surgery, may result in a decreased dose requirement. CONCLUSIONS: For patients after bariatric surgery, close monitoring of both the clinical presentation and plasma thyroid-stimulating hormone and T4 levels is strongly advised. Better understanding and awareness of the science presented in this article may help to avoid preventable complications and provide optimal patient care.
BACKGROUND: Bariatric surgery can lead to changes in the oral absorption of many drugs. Levothyroxine is a narrow therapeutic drug for hypothyroidism, a common condition among patients with obesity. OBJECTIVE: The purpose of this work was to provide a mechanistic overview of levothyroxine absorption, and to thoroughly analyze the expected effects of bariatric surgery on oral levothyroxine therapy. METHODS: We performed a systematic review of the relevant literature reporting the effects of bariatric surgery on oral levothyroxine absorption and postoperative thyroid function. A PubMed search for relevant keywords resulted in a total of 14 articles reporting levothyroxine status before versus after bariatric surgery. RESULTS: Different mechanisms may support opposing trends as to levothyroxine dose adjustment postsurgery. On the one hand, based on impaired drug solubility/dissolution attributable to higher gastric pH as well as reduced gastric volume, compromised levothyroxine absorption is expected. On the other hand, the great weight loss, and altered set-point of thyroid hormone homeostasis with decreased thyroid-stimulating hormone after the surgery, may result in a decreased dose requirement. CONCLUSIONS: For patients after bariatric surgery, close monitoring of both the clinical presentation and plasma thyroid-stimulating hormone and T4 levels is strongly advised. Better understanding and awareness of the science presented in this article may help to avoid preventable complications and provide optimal patient care.