title: In vitro inhibition and induction of human liver cytochrome p450 enzymes by milnacipran.
abstract: Milnacipran (Savella) inhibits both norepinephrine and serotonin reuptake and is distinguished by a nearly 3-fold greater potency in inhibiting norepinephrine reuptake in vitro compared with serotonin. We evaluated the ability of milnacipran to inhibit and induce human cytochrome P450 enzymes in vitro. In human liver microsomes, milnacipran did not inhibit CYP1A2, 2B6, 2C8, 2C9, 2C19, or 2D6 (IC(50) >or= 100 microM); whereas, a comparator with dual reuptake properties [duloxetine (Cymbalta)] inhibited CYP2D6 (IC(50) = 7 microM) and CYP2B6 (IC(50) = 15 microM) with a relatively high potency. Milnacipran inhibited CYP3A4/5 in a substrate-dependent manner (i.e., midazolam 1'-hydroxylation IC(50) approximately 30 microM; testosterone 6beta-hydroxylation IC(50) approximately 100 microM); whereas, duloxetine inhibited both CYP3A4/5 activities with equal potency (IC(50) = 37 and 38 microM, respectively). Milnacipran produced no time-dependent inhibition (<10%) of P450 activity, whereas duloxetine produced time-dependent inhibition of CYP1A2, 2B6, 2C19, and 3A4/5. To evaluate P450 induction, freshly isolated human hepatocytes (n = 3) were cultured and treated once daily for 3 days with milnacipran (3, 10, and 30 microM), after which microsomal P450 activities were measured. Whereas positive controls (omeprazole, phenobarbital, and rifampin) caused anticipated P450 induction, milnacipran had minimal effect on CYP1A2, 2C8, 2C9, or 2C19 activity. The highest concentration of milnacipran (30 microM; >10 times plasma C(max)) produced 2.6- and 2.2-fold increases in CYP2B6 and CYP3A4/5 activity (making it 26 and 34% as effective as phenobarbital and rifampin, respectively). Given these results, milnacipran is not expected to cause clinically significant P450 inhibition or induction.
authors.affiliation: XenoTech LLC, Lenexa, KS 66219, USA.
authors.forename: Brandy L
authors.initials: BL
authors.lastname: Paris
authors.forename: Brian W
authors.initials: BW
authors.lastname: Ogilvie
authors.forename: Julie A
authors.initials: JA
authors.lastname: Scheinkoenig
authors.forename: Florence
authors.initials: F
authors.lastname: Ndikum-Moffor
authors.forename: Remi
authors.initials: R
authors.lastname: Gibson
authors.forename: Andrew
authors.initials: A
authors.lastname: Parkinson
mesh_terms: D000368:Aged; D000897:Anti-Ulcer Agents / Q000494:pharmacology; D000995:Antitubercular Agents / Q000494:pharmacology; D003521:Cyclopropanes / Q000494:pharmacology*; D019388:Cytochrome P-450 CYP1A2 / Q000378:metabolism; D019389:Cytochrome P-450 CYP2D6 / Q000378:metabolism; D051544:Cytochrome P-450 CYP3A / Q000378:metabolism; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000187:drug effects* / Q000378:metabolism; D004347:Drug Interactions; D004790:Enzyme Induction / Q000187:drug effects; D022781:Hepatocytes / Q000187:drug effects* / Q000201:enzymology; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects* / Q000201:enzymology; D008874:Midazolam / Q000494:pharmacology; D008875:Middle Aged; D000078764:Milnacipran; D009853:Omeprazole / Q000494:pharmacology; D017367:Selective Serotonin Reuptake Inhibitors / Q000494:pharmacology*; D013739:Testosterone / Q000494:pharmacology
chemical_list: D000897:Anti-Ulcer Agents; D000995:Antitubercular Agents; D003521:Cyclopropanes; D019388:Cytochrome P-450 CYP1A2; D019389:Cytochrome P-450 CYP2D6; D051544:Cytochrome P-450 CYP3A; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System; D007004:Hypoglycemic Agents; D008874:Midazolam; D000078764:Milnacipran; D009853:Omeprazole; D017367:Selective Serotonin Reuptake Inhibitors; D013739:Testosterone; C510163:CYP3A4 protein, human