[First-pass metabolism of acetaminophen in thyroxine treated rats].
The study on the first-pass metabolism of acetaminophen was carried out in normal and thyroxine-treated rats, administered 30 mg/kg by three routes of intravenous, intraperitoneal, and oral one. Unconjugated acetaminophen and two major metabolites, glucuronide and sulfate in the plasma and urine were then measured 5 and 24 h after the administration, respectively. It was found that there was no difference in total percentage of excreted amount, independent of the routes for administration, between normal and thyroxine-treated rats. This fact shows that acetaminophen is absorbed completely from the gastrointestinal tract. However, it was also found that the extraction ratio of gastrointestinal tract in thyroxine-treated rats became smaller, and that the volume of distribution and total body clearance became larger than those in normal rats. The first-pass metabolism of acetaminophen was found to be influenced by the continuous administration of thyroxine.
Zhu
C Y
CY
Department of Hospital Pharmacy, Toyama Medical and Pharmaceutical University, Japan.
Hirate
J
J
Kanamoto
I
I
Nakagawa
T
T
Adachi
I
I
Horikoshi
I
I
Bhargava
V O
VO
D000082:Acetaminophen / Q000008:administration & dosage / Q000493:pharmacokinetics*; D000284:Administration, Oral; D000818:Animals; D004347:Drug Interactions; D007274:Injections, Intraperitoneal; D007275:Injections, Intravenous; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D013974:Thyroxine / Q000008:administration & dosage / Q000494:pharmacology*
D000082:Acetaminophen; D013974:Thyroxine