Peak plasma concentrations (Cmax) are reached within 1–3 hours of taking immediate-release metformin and 4–8 hours with extended-release formulations. The plasma protein binding of metformin is negligible, as reflected by its very high apparent volume of distribution (300–1000 L after a single dose). Steady state is usually reached in 1–2 days.Metformin has acid dissociation constant values (pKa) of 2.8 and 11.5, so it exists very largely as the hydrophilic cationic species at physiological pH values. The metformin pKa values make it a stronger base than most other basic medications with less than 0.01% nonionized in blood. Furthermore, the lipid solubility of the nonionized species is slight as shown by its low logP value (log(10) of the distribution coefficient of the nonionized form between octanol and water) of −1.43. These chemical parameters indicate low lipophilicity and, consequently, rapid passive diffusion of metformin through cell membranes is unlikely. As a result of its low lipid solubility it requires the transporter SLC22A1 in order for it to enter cells. The logP of metformin is less than that of phenformin (−0.84) because two methyl substituents on metformin impart lesser lipophilicity than the larger phenylethyl side chain in phenformin. More lipophilic derivatives of metformin are presently under investigation with the aim of producing prodrugs with superior oral absorption than metformin.Metformin is not metabolized. It is cleared from the body by tubular secretion and excreted unchanged in the urine; it is undetectable in blood plasma within 24 hours of a single oral dose. The average elimination half-life in plasma is 6.2 hours.
Creon may refer to:

Greek history
Creon, the first annual eponymous archon of Athens, 682–681 BC

Greek mythology
Creon (king of Thebes), mythological king of Thebes
Creon (king of Corinth), father of Creusa/Glauce in Euripides Medea
Creon, son of Heracles by a daughter of Thespius, king of Thespiae

Medicine
Creon, a brand name of a pancreatic enzymes medication

Places
Créon, a commune in the Gironde department in France
Créon-dArmagnac, a commune in the Landes department in France

Other
Creon a genus of butterfly, in the family Lycaenidae, containing the species Broadtail royal
USS Creon (ARL-11), a World War II U.S. Navy landing craft repair ship

See also
Kreon, a DC Comics character
Kreon, a minifigure (similar to Lego minifigure) from Kre-O construction toys manufactured by Oxford, a Korean company, and marketed by Hasbro