title: Dose-dependent pharmacokinetics of all-trans-retinoic acid.
abstract: BACKGROUND
  Orally administered all-trans-retinoic acid (all-trans-RA) can induce remission in a high proportion of patients with acute promyelocytic leukemia.
  
  
  OBJECTIVE
  To further define the drug's pharmacokinetics, a study of intravenous all-trans-RA was performed in rhesus monkeys.
  
  
  METHODS
  A total of nine monkeys received intravenous bolus injections of all-trans-RA. Three different doses (20, 50, and 100 mg/m2) were each tested in three monkeys. Blood samples for determination of all-trans-RA concentration were obtained prior to drug administration and at 5, 10, 15, 30, 45, 60, 75, 90, 120, 150, 180, 240, 360, and 480 minutes after drug administration.
  
  
  RESULTS
  Plasma disappearance of all-trans-RA was characterized by three distinct phases: a brief, initial exponential decline, followed by a relative plateau in the disappearance curve (the duration of which was dose dependent), and finally a terminal exponential decay. This profile is consistent with a capacity-limited (saturable) elimination process. The first-order (terminal) half-life for all-trans-RA averaged 19 minutes, and the mean clearances were 77, 52, and 59 mL/min for the 20-, 50-, and 100-mg/m2 dose groups, respectively. The mean +/- SD Michaelis constant (Km) for the capacity-limited process was 3.2 +/- 1.9 microM.
  
  
  CONCLUSIONS
  Peak plasma concentrations following oral administration of 45 mg/m2 all-trans-RA in humans approach the Km for the capacity-limited process; thus, the dose-dependent pharmacokinetics of all-trans-RA described here may occur within the clinically used dosage range.
authors.affiliation: Pediatric Branch, National Cancer Institute, Bethesda, Md. 20892.
authors.forename: P C
authors.initials: PC
authors.lastname: Adamson
authors.forename: F M
authors.initials: FM
authors.lastname: Balis
authors.forename: M A
authors.initials: MA
authors.lastname: Smith
authors.forename: R F
authors.initials: RF
authors.lastname: Murphy
authors.forename: K A
authors.initials: KA
authors.lastname: Godwin
authors.forename: D G
authors.initials: DG
authors.lastname: Poplack
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D007275:Injections, Intravenous; D007700:Kinetics; D008253:Macaca mulatta; D013997:Time Factors; D014212:Tretinoin / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*
chemical_list: D014212:Tretinoin