|show drug details|
|5-25-10-00059 (Beilstein Handbook Reference)|
|shortness of breath||0.01|
|congestive heart failure||0.0010|
|restless leg syndrome||0.0010|
|pelvic inflammatory disease||0|
|show target details|
|Cytochrome P450 3A3|
|Cytochrome P450 3A4|
|PDB IDs:||1TQN 1W0E 1W0F 1W0G 2J0D 2V0M |
|Ki: ||Kd:||Ic 50:||Ec50/Ic50:|
Substrate-dependent modulation of CYP3A4 catalytic activity: analysis of 27 test compounds with four fluorometric substrates.. D M Stresser; A P Blanchard; S D Turner; J C Erve; A A Dandeneau; V P Miller; C L Crespi (2000) Drug metabolism and disposition: the biological fate of chemicals display abstract
Inhibition of cytochrome P450 catalytic activity is a principal mechanism for pharmacokinetic drug-drug interactions. Rapid, in vitro testing for cytochrome P450 inhibition potential is part of the current paradigm for identifying drug candidates likely to give such interactions. We have explored the extent that qualitative and quantitative inhibition parameters are dependent on the cytochrome P450 (CYP) 3A4 probe substrate. Inhibition potential (e.g., IC(50) values from 8-point inhibition curves) or activation potential for most compounds varied dramatically depending on the fluorometric probe substrates for CYP3A4 [benzyloxyresorufin (BzRes), 7-benzyloxy-4-trifluoromethylcoumarin (BFC), 7-benzyloxyquinoline (BQ), and dibenzylfluorescein (DBF)]. For 21 compounds that were primarily inhibitors, the range of IC(50) values for the four substrates varied from 2.1- to 195-fold with an average of 29-fold. While the rank order of sensitivity among the fluorometric substrates varied among the individual inhibitors, on average, BFC dealkylation was the most sensitive to inhibition, while BQ dealkylation was least sensitive. Partial inhibition was observed with BzRes and BQ but not for BFC and DBF. BzRes was more prone to activation, whereas dramatic changes in IC(50) values were observed when the BQ concentration was below the S(50). Three different correlation analyses indicated that IC(50) values with BFC, BQ, and DBF correlated well with each other, whereas the response with BzRes correlated more weakly with the other substrates. One of these correlation analyses was extended to the percent inhibition of 10 microM inhibitor with the standard CYP3A4 probe substrates testosterone, midazolam, and nifedipine. In this analysis the responses with BQ, BFC and DBF correlated well with testosterone and midazolam but more poorly with nifedipine. In the aggregate, BFC and DBF appear more suitable as an initial screen for CYP3A4 inhibition. However, the substrate-dependent effects reported here and by others indicate that all CYP3A4 inhibition data should be interpreted with caution.
Cytochrome P450 3A-mediated metabolism of buspirone in human liver microsomes.. Mingshe Zhu; Weiping Zhao; Humberto Jimenez; Donglu Zhang; Suresh Yeola; Renke Dai; Nimish Vachharajani; James Mitroka (2005) Drug metabolism and disposition: the biological fate of chemicals display abstract
This study was carried out to determine the metabolic pathways of buspirone and cytochrome P450 (P450) isoform(s) responsible for buspirone metabolism in human liver microsomes (HLMs). Buspirone mainly underwent N-dealkylation to 1-pyrimidinylpiperazine (1-PP), N-oxidation on the piperazine ring to buspirone N-oxide (Bu N-oxide), and hydroxylation to 3'-hydroxybuspirone (3'-OH-Bu), 5-hydroxybuspirone (5-OH-Bu), and 6'-hydroxybuspirone (6'-OH-Bu) in HLMs. The apparent K(m) values for buspirone metabolite formation in pooled HLMs were 8.7 (1-PP), 34.0 (Bu N-oxide), 4.3 (3'-OH-Bu), 11.4/514 (5-OH-Bu), and 8.8 microM (6'-OH-Bu). CYP3A inhibitor ketoconazole (1 microM) completely inhibited the formation of all major metabolites in HLMs (0-16% of control), whereas the chemical inhibitor selective to other P450 isoforms had little or no inhibitory effect. Recombinant CYP3A4, CYP3A5, and CYP2D6 exhibited buspirone oxidation activities among nine P450 isoforms tested. The overall metabolism rate of 5 microM buspirone by CYP3A4 was 18-fold greater than that by CYP2D6 and 35-fold greater than that by CYP3A5. In a panel of HLMs from 16 donors, buspirone metabolism correlated well CYP3A activity (r2 = 0.85-0.96, rho < 0.0005), but not the activities of other P450 isoforms. The metabolism rates of buspirone in CYP2D6 poor-metabolizer genotype HLMs were comparable to those in pooled HLMs. Taken together, these data suggest that CYP3A, mostly likely CYP3A4, is primarily responsible for the metabolism of buspirone in HLMs.
Plasma buspirone concentrations are greatly increased by erythromycin and itraconazole.. K T Kivist÷; T S Lamberg; T Kantola; P J Neuvonen (1997) Clinical pharmacology and therapeutics display abstract
BACKGROUND: The oral bioavailability of buspirone is very low as a result of extensive first-pass metabolism. Erythromycin and itraconazole are potent inhibitors of CYP3A4, and they increase plasma concentrations and effects of certain drugs, for example, oral midazolam and triazolam. The possible interactions of buspirone with erythromycin and itraconazole have not been studied before. METHODS: The pharmacokinetics and pharmacodynamics of buspirone were investigated in a randomized, double-blind, double-dummy crossover study with three phases. Eight young healthy volunteers took either 1.5 gm/day erythromycin, 200 mg/day itraconazole, or placebo orally for 4 days. On day 4, 10 mg buspirone was administered orally. Timed blood samples were collected up to 18 hours, and the effects of buspirone were measured with four psychomotor tests up to 8 hours. RESULTS: Erythromycin and itraconazole increased the mean area under the plasma concentration-time curve from time zero to infinity [AUC(0-infinity] of buspirone about sixfold (p < 0.05) and 19-fold (p < 0.01), respectively, compared with placebo. The mean peak plasma concentration (Cmax) of buspirone was increased about fivefold (p < 0.01) and 13-fold (p < 0.01) by erythromycin and itraconazole, respectively. These interactions were evident in each subject, although a striking interindividual variability in the extent of both interactions was observed. The elimination half-life of buspirone did not seem to be prolonged by either erythromycin or itraconazole. The effect of itraconazole on the Cmax and AUC(0-infinity) of buspirone was significantly (p < 0.01) greater than that of erythromycin. The greatly elevated plasma buspirone concentrations resulted in increased (p < 0.05) pharmacodynamic effects (as measured by the Digit Symbol Substitution test and the Critical Flicker Fusion test) and in side effects of buspirone. CONCLUSIONS: Both erythromycin and itraconazole greatly increased plasma buspirone concentrations, obviously by inhibiting its CYP3A4-mediated first-pass metabolism. These pharmacokinetic interactions were accompanied by impairment of psychomotor performance and side effects of buspirone. The dose of buspirone should be greatly reduced during concomitant treatment with erythromycin, itraconazole, or other potent inhibitors of CYP3A4.