Sucralfate causes malabsorption of L-thyroxine.
OBJECTIVE
To determine if sucralfate causes malabsorption of L-thyroxine.


METHODS
Five healthy volunteers ingested L-thyroxine, 1,000 micrograms, 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 micrograms (95% confidence interval (CI): 515-1,074 micrograms). Coadministration of sucralfate, 1 g, with L-thyroxine reduced thyroid hormone absorption to 225 micrograms (95% CI: 151-299 micrograms) (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.
Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland.
S I
SI
Sherman
E T
ET
Tielens
P W
PW
Ladenson
D000328:Adult; D005260:Female; D006801:Humans; D007408:Intestinal Absorption / Q000187:drug effects; D008286:Malabsorption Syndromes / Q000139:chemically induced*; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D013392:Sucralfate / Q000009:adverse effects*; D013974:Thyroxine / Q000378:metabolism*
D013392:Sucralfate; D013974:Thyroxine