title: Kinetics and metabolism of pyrazolones (propyphenazone, aminopyrine and dipyrone).
abstract: 1 Propyphenazone 220 mg was administered orally to volunteers. Maximum plasma concentrations between 1.5 microgram/ml and 3.5 micrograms/ml were found 30 min later. After comparable doses plasma concentrations in dog and rabbit were lower. The distribution volumes were 2 l/kg. 2 The major metabolic route of propyphenazone is demethylation. The main urinary metabolite is the enolglucuronide of N-(2)-demethylpropyphenazone. 3 Aminopyrine is rapidly and almost completely absorbed after oral administration. Maximum plasma concentrations of 10 microgram/ml are reached 1.5 h after a 500 mg dose. The biological half-life is 2-3 h, the relative distribution volume 60% on average, and binding to plasma proteins approximately 15%. 4 Unchanged aminopyrine is only excreted in small quantities. The major routes of metabolism are demethylation (4-methylaminoantipyrine and 4-aminoantipyrine) and acylation (4-acetyl and 4-formylaminoantipyrine). There are other biotransformation products. 5 After oral administration of [14C]-dipyrone 480 mg the maximum serum concentration of 13.4 +/- 0.8 microgram/ml occurred at 1-1.5 hours. 6 Dipyrone was not detectable in serum or urine. Four of seven metabolites were identified, and were identical with the main metabolites of aminopyrine.
mesh_terms: D000284:Administration, Oral; D000632:Aminopyrine / Q000378:metabolism; D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000378:metabolism*; D000983:Antipyrine / Q000031:analogs & derivatives / Q000378:metabolism; D001711:Biotransformation; D004177:Dipyrone / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D010084:Oxidation-Reduction; D011720:Pyrazoles / Q000378:metabolism*; D013488:Suppositories
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D011720:Pyrazoles; D013488:Suppositories; D000632:Aminopyrine; D004177:Dipyrone; C009077:propyphenazone; D000983:Antipyrine