Sucralfate causes malabsorption of L-thyroxine

purpose: To determine if sucralfate causes malabsorption of L-thyroxine. patients and methods: Five healthy volunteers ingested L-thyroxine, 1,000 μg, administered orally (1) without sucralfate, (2) with sucralfate, 1 g, and (3) 8 hours after sucralfate, 2 g. The amount of L- thyroxine absorbed was calculated from the peak increase in serum T₄ levels within 6 hours of hormone ingestion multiplied by the volume of distribution for the hormone. results: Peak absorption of L-thyroxine in the absence of sucralfate was 796 μg (95% confidence interval (CI): 515 - 1,074 μg). Coadministration of sucralfate, 1 g, with L- thyroxine reduced thyroid hormone absorption to 225 μg (95% Cl: 151 - 299 μg) (P = 0.0029 compared with control). Peak hormone absorption was delayed 2 hours by simultaneous sucralfate ingestion. Separation of administered L-thyroxine and sucralfate doses by 8 hours returned hormone absorption to control values. Maximum T₃ levels did not differ, regardless of drug regimen, but suppression of thyroid-stimulating hormone (TSH) by L- thyroxine was reduced by coadministration of sucralfate. conclusions: Sucralfate causes malabsorption of L-thyroxine, presumably by intraluminal binding of hormone.