TY - JOUR T1 - Toxicokinetics and Metabolism of<em>N-</em>[<sup>14</sup>C]Methylpyrrolidone in Male Sprague-Dawley Rats. A Saturable NMP Elimination Process JF - Drug Metabolism and Disposition JO - Drug Metab Dispos SP - 1418 LP - 1424 DO - 10.1124/dmd.30.12.1418 VL - 30 IS - 12 AU - Jean-Paul Payan AU - Dominique Beydon AU - Jean-Paul Fabry AU - Isabelle Boudry AU - Benoit Cossec AU - Elisabeth Ferrari Y1 - 2002/12/01 UR - http://dmd.aspetjournals.org/content/30/12/1418.abstract N2 - This study evaluated the toxicokinetics ofN-[14C]methylpyrrolidone ([14C]NMP) after intravenous administration (0.1, 1, 10, 100, and 500 mg/kg, in saline solution) or topical application (20 and 40 μl/cm2; 10 cm2, neat) in haired male Sprague-Dawley rats. Whatever the dose, unchanged NMP was intensively distributed into the body with a volume of distribution of 69% of body weight. After this phase, unchanged NMP declined almost linearly with time for 3 to 4 h after administration and then followed a mono-exponential function (t½ = 0.8 h) for the three lowest doses. The maximal plasma level of 5-hydroxy-N-methylpyrrolidone (5-HNMP), the main metabolite, was reached 4 to 6 h later for the three lowest doses and 8 to 24 h later for the highest doses. These findings indicate that the elimination of NMP is governed by a saturable metabolism process. The Michaelis-Menten parameters estimated from plasma levels of unchanged NMP were 2 mM and 3.8 mg/h, respectively. Between 4 and 10% of the administered doses were excreted in the urine as unchanged NMP. Urinary clearance of NMP (0.03 to 0.07 ml/min) indicates intensive tubular reabsorption. 5-HNMP was the main urinary metabolite and accounted for 42 to 55% of the administered doses. Its maximal urinary excretion occurred between 4 and 6 h after administration of the three lowest doses and between 8 and 24 h for the two highest doses. Urinary clearance (0.9 to 1.3 ml/min) was compatible with renal elimination by simple glomerular filtration. The American Society for Pharmacology and Experimental Therapeutics ER -