Effects of cytochrome P450 inducers and inhibitors on the pharmacokinetics of intravenous furosemide in rats: involvement of CYP2C11, 2E1, 3A1 and 3A2 in furosemide metabolism.

OBJECTIVES: It has been reported that the non-renal clearance of furosemide was significantly faster in rats pretreated with phenobarbital but was not altered in rats pretreated with 3-methylcholanthrene. However, no studies on other cytochrome P450 (CYP) isozymes have yet been reported in rats. METHOD: Furosemide 20 mg/kg was administered intravenously to rats pretreated with various CYP inducers--3-methylcholanthrene, orphenadrine citrate and isoniazid, inducers of CYP1A1/2, 2B1/2 and 2E1, respectively, in rats--and inhibitors--SKF-525A (a non-specific inhibitor of CYP isozymes), sulfaphenazole, cimetidine, quinine hydrochloride and troleandomycin, inhibitors of CYP2C6, 2C11, 2D and 3A1/2, respectively, in rats. KEY FINDINGS: The non-renal clearance of furosemide was significantly faster (55.9% increase) in rats pretreated with isoniazid, but slower in those pretreated with cimetidine or troleandomycin (38.5% and 22.7% decreases, respectively), than controls. After incubation of furosemide with baculovirus-infected insect cells expressing CYP2C11, 2E1, 3A1 or 3A2, furosemide was metabolized via CYP2C11, 2E1, 3A1 and 3A2. CONCLUSIONS: These findings could help explain possible pharmacokinetic changes of furosemide in various rat disease models (where CYP2C11, 2E1, 3A1 and/or CYP3A2 are altered) and drug-drug interactions between furosemide and other drugs (mainly metabolized via CYP2C11, 2E1, 3A1 and/or 3A2).

A novel administration route for edaravone: I. Effects of metabolic inhibitors on skin permeability of edaravone.

We examined the effects of metabolic inhibitors on skin permeation of edaravone. SKF-525A, diclofenac sodium (DIC) and indomethacin (IND) were added to supernatant fluid (SF) of hairless rat (HR) skin homogenate. L-Cysteine (L-Cys) and benzotriazole (BTA), as pharmaceutical additives, were added to HR skin homogenate SF, and incubated at 37 degrees C for 30 min. K(m) and V(max) values were calculated. For determination of edaravone skin permeation from edaravone/hydroxypropyl-beta-cyclodextrin (HPbetaCD) complex solution, HR skin was placed in a Franz diffusion cell, and kept at 37 degrees C. Edaravone/HPbetaCD solution that contained L-Cys was put into the donor side. The relative activity in skin homogenate SF after co-treatment with IND and SKF-525A decreased to 40.8% of the control. However, DIC and IND had a weak inhibitory effect. For inhibition of edaravone metabolism, L-Cys and BTA had no effect on K(m) value, but V(max) was significantly decreased compared with controls (*P<0.05, Tukey-Kramer test). The edaravone skin permeation rate and permeability coefficient from edaravone/HPbetaCD complex solution with inhibitor were significantly increased compared with those without inhibitor. We suggest that the metabolism inhibitor was useful for the transdermal delivery of edaravone.

Hepatobiliary excretion of berberine.

Berberine is a bioactive herbal ingredient isolated from the roots and bark of Berberis aristata or Coptis chinensis. To investigate the detailed pharmacokinetics of berberine and its mechanisms of hepatobiliary excretion, an in vivo microdialysis coupled with high-performance liquid chromatography was performed. In the control group, rats received berberine alone; in the drug-treated group, 10 min before berberine administration, the rats were injected with cyclosporin A (CsA), a P-glycoprotein (P-gp) inhibitor; quinidine, both organic cation transport (OCT) and P-gp inhibitors; SKF-525A (proadifen), a cytochrome P450 inhibitor; and probenecid to inhibit the glucuronidation. The results indicate that berberine displays a linear pharmacokinetic phenomenon in the dosage range from 10 to 20 mg kg(-1), since a proportional increase in the area under the concentration-time curve (AUC) of berberine was observed in this dosage range. Moreover, berberine was processed through hepatobiliary excretion against a concentration gradient based on the bile-to-blood distribution ratio (AUC(bile)/AUC(blood)); the active berberine efflux might be affected by P-gp and OCT since coadministration of berberine and CsA or quinidine at the same dosage of 10 mg kg(-1) significantly decreased the berberine amount in bile. In addition, berberine was metabolized in the liver with phase I demethylation and phase II glucuronidation, as identified by liquid chromatography/tandem mass spectrometry. Also, the phase I metabolism of berberine was partially reduced by SKF-525A treatment, but the phase II glucuronidation of berberine was not obviously affected by probenecid under the present study design.

Pharmacokinetic changes of M1, M2, M3 and M4 after intravenous administration of a new anthracycline, DA-125, to rats pretreated with phenobarbital, 3-methylcholanthrene, chloramphenicol, or SKF-525A.

The pharmacokinetics of M1-M4, the metabolites of a new anthracycline antineoplastic agent, DA-125, were compared after intravenous (i.v.) administration of DA-125, 15 mg kg-1, to rats pretreated with enzyme inducers, such as phenobarbital (PBT, n = 14) and 3-methylcholanthrene (MCT, n = 15), or enzyme inhibitors, such as SKF-525A (SKT, n = 11) and chloramphenicol (CMT, n = 15), and to their control rats (n = 15 for PBC, CMC or SKC, and n = 11 for MCC). After i.v. administration of DA-125, the plasma concentrations of both M1 and M2 declined slowly from 1 to 2 h onwards to 8 h in all groups of rats due to the continuous formation of M2 from M1. The AUC0-8 h of M1 (47.1 versus 7.85 micrograms min mL-1) and M2 (20.7 versus 44.3 micrograms min mL-1) decreased significantly in the PBT group compared to those in the PBC group. However, the corresponding value of only M1 (74.6 versus 89.9 micrograms min mL-1) decreased significantly in the MCT group. The above data indicate that metabolism of M1 is increased by pretreatment with both PB and 3-MC, and that of M2 with PB, but not with 3-MC. The AUC0-8 h of both M1 (126 versus 78.5 micrograms min mL-1) and M2 (69.2 versus 44.3 micrograms min mL-1) increased significantly in the SKT group compared to the SKC group. However, the corresponding values were not significantly different between CMC and CMT groups. The above data indicate that the metabolism of both M1 and M2 is inhibited by pretreatment with SKF-525A, but not with CM.

Effects of feeding Artemisia filifolia and Helenium flexuosum on rabbit cytochrome P450 isozymes.

Six groups of 4 rabbits each were treated as follows: Control; phenobarbital (PB); 3-methylcholanthrene (3MC); proadifen hydrochloride (SKF-525A); Artemisia filifolia and Helenium flexuosum. Prototype P450 inducers (PB and 3MC) increased basal hepatic cytochrome P450 content by 2-3 fold whereas the P450 inhibitor (SKF-525A) had no effect on basal cytochrome P450 content. PB-induction of hepatic microsomes significantly increased the rate of dealkylation of long alkyl chain alkoxyresorufin ethers, benzyloxyresorufin and pentoxyresorufin 47-fold and 17-fold, respectively, but had little or no effect on short alkyl chains. 3MC-induction of microsomes increased dealkylation of all alkoxyresorufin ethers tested, preferentially dealkylating ethers with short alkyl chain in the order: methoxy > ethoxy > propoxy. Artemisia filifolia or Helenium flexuosum had no effect on basal hepatic cytochrome P450 content. However, microsomal dealkylation activity of short alkyl chain alkoxyresorufin ethers (methoxy, ethoxy and propoxy) was inhibited approximately 50%. When these plants are eaten for several days, they may inhibit biotransformation processes in herbivores through the same isoenzymes induced by 3MC.

Protective effect of colchicine on acute liver damage induced by CCl4. Role of cytochrome P-450.

The aim of this work was to study if colchicine protects against. CCl4-induced changes in hepatic biochemical parameters by reducing cytochrome P-450, by comparing the effects of colchicine and SKF 525-A, a well-known inhibitor of cytochrome P-450. Our results show that both drugs reduced the cytochrome P-450 content and p-nitroanisole o-demethylase activity to the same extent. However, colchicine afforded a total protection from markers of liver injury, while SKF 525-A protected only partially. The difference in the hepatoprotective activity of both drugs indicates that the beneficial effect of colchicine cannot be attributed solely to the inhibition of the activation of CCl4. Other actions, perhaps at the level of the propagation of lipid peroxidation or a 'membrane-stabilizing' effect cannot be ruled out.

Gonadal hormones affect the hypothermia induced by serotonin1A (5-HT1A) receptor activation.

Subcutaneous injection of 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT) in mice caused hypothermia which was antagonized by pindolol. The hypothermic effect of 8-OH-DPAT was pronounced in female than in male mice. The sex difference in the hypothermic effect was also observed after pretreatment with proadifen. The hypothermic effect of 8-OH-DPAT was attenuated by ovariectomy. In the ovariectomized mice, the effect of 8-OH-DPAT on rectal temperature was enhanced by chronic estradiol and the enhancement was blocked by simultaneous administration of testosterone. In male mice the hypothermic effect of 8-OH-DPAT was enhanced by castration. These results suggest that gonadal hormones affect the 5-HT1A receptor-mediated response.

Effect of co-administration of interferon inducer, polyriboinosinic acid-polyribocytidylic acid, with SKF 525-A on hepatic drug metabolizing enzymes of rats.

The protective effect of SKF 525-A on the suppression of cytochrome P-450 content and monooxygenase activities by treatment with CoCl2 and polyriboinosinic acid-polyribocytidylic acid [poly(I.C] was compared as a part of studies of suppression of drug metabolizing enzymes by interferon inducers. Induction of heme oxygenase activity by CoCl2 and poly (I.C) was not altered by simultaneous treatment with SKF 525-A. Depression of cytochrome P-450 content and benzphetamine N-demethylase activity by treatment with CoCl2 was prevented by co-treatment with SKF 525-A. This effect was explained by the prevention of release of heme from cytochrome P-450 by forming metabolic intermediate complexes with metabolites of SKF 525-A. On the other hand, poly(I.C) significantly suppressed P-450 content and benzphetamine N-demethylase and benzo [a] pyrene hydroxylase activities, even under simultaneous treatment with SKF 525-A. This inhibition by poly (I.C) was accompanied by weak staining of proteins corresponding to cytochrome P-450 in SDS gel electrophoresis. In addition, the activity of non-heme enzyme, 4-hydroxybiphenyl glucuronyltransferase, was suppressed by treatment with poly (I.C) but not by CoCl2-treatment. These findings strongly suggested that, unlike CoCl2, poly (I.C) suppressed cytochrome P-450 content and monooxygenase activities due to decreased synthesis or increased degradation of the apoprotein of cytochrome P-450 with slight contribution of the induced heme oxygenase.

Effects of co-administration of monomethylaminoantipyrine with diethylaminoethyl 2,2-diphenylvalerate (SKF 525-A) on gamma-glutamyltranspeptidase, glutathione S-transferase and hepatic drug metabolizing enzyme activities in rats.

4-Monomethylaminoantipyrine (MAA)-induced increase of hepatic drug metabolizing enzymes was suppressed by SKF 525-A. This may be due to the partial binding of SKF 525-A to a portion of cytochrome P-450. On the other hand, glutathione S-transferase and gamma-glutamyltranspeptidase (gamma-GTP) activities of rat liver were both induced by repeated administration of MAA in combination with SKF 525-A. In addition, under the same condition, glutathione level in rat liver was significantly decreased.

Mianserin: is the intraperitoneal route of administration the best?

A 1 h pretreatment with s.c. mianserin (0.5 mg kg-1) markedly blunted the oedema of the rat paw induced by the subplantar injection of 5-HT (5 micrograms). In contrast, i.p. mianserin (same dose) failed to modify 5-HT-induced oedema. However, pretreatment with SKF-525-A (40 mg kg-1) resulted in a profound potentiation of the action of i.p. mianserin, the effect of the combination of SKF-525-A and i.p. mianserin rivaling that of s.c. mianserin. It is concluded that i.p. mianserin is metabolized by the rat liver to compounds which possess a reduced propensity to block peripheral 5-HT receptors and that the i.p. route of administration is not to be recommended when mianserin is being studied as a 5-HT receptor antagonist in the rat.

[Activity of nonspecific hepatic oxidases and the biological effects of the antineoplastic antibiotic adriamycin]. / Aktivnost' nespetsificheskikh oksidaz pecheni i biologicheskie éffekty protivoopukholevogo antibiotika adriamitsina.

It was shown in male CBA mice that toxic doses (15 and 20 mg/kg) of adriamycin (AD) inhibited the activity of nonspecific liver oxidases and noticeably increased the duration of the animals' sleep after injection of hexenal which is a substrate of this enzymatic system. The inhibitory effect of AD remained unchanged in the course of 9 days of the experiment. The nontoxic dose of AD (5 mg/kg) inhibited the activity of the enzymatic system on the 2nd--3rd days after the injection of the drug. Meanwhile the activity of the enzymatic system returned to the level seen in intact animals by days 5--6. The toxic action of AD declined on activation of nonspecific liver oxidases with phenobarbital and rose as a result of administering the inhibitor SKF 525-A. The authors discuss whether it is possible to use the data obtained for clinical application of AD.

[Drug interaction on antitumor drugs I. Antitumor activity of cyclophosphamide in mice consecutively administered aminopyrine, chlorpromazine, or morphine (author's transl)].

Antitumor activity and lethality of cyclophosphamide alone and in combination with several drugs were investigated in male ddY mice. The antitumor activity was estimated by weighing the solid tumor on the 15th day after Ehrlich ascites cell inoculation. Pentobarbital induced sleeping time for monitoring the activity of hepatic drug-metabolizing enzymes was defined as the time between the loss and the recovery of the righting reflex. Consecutive administration of pentobarbital shortened the pentobarbital sleeping time and increased the antitumor activity after cyclophosphamide. On the contrary, a single administration of SKF 525A or cycloheximide prolonged the pentobarbital sleeping time significantly and decreased the antitumor activity after cyclophosphamide. Consecutive administration of aminopyrine, or chlorpromazine shortened the pentobarbital sleeping time and increased the antitumor activity after cyclophosphamide. These results indicate that aminopyrine and chlorpromazine may increase the levels of the hepatic drug-metabolizing components and may activate cyclophosphamide by conversion to an active form. Effect of a consecutive administration of morphine on the pentobarbital sleeping time and the antitumor activity was uncertain in individual cases. On the other hand, aminopyrine, chlorpromazine, or morphine in consecutive administration increased the lethality of cyclophosphamide.

Opiate properties of SKF 525A.

SKF 525A, a classical inhibitor of microsomal drug-metabolizing enzymes, is structurally similar to the diphenylpropylamine analgesics, and certain reported effects in animals resemble those produced by opiate drugs. In an opiate radioreceptor assay, SKF 525A was 50 times less potent than methadone in the absence of sodium and 10 times less potent in the prescence of sodium. The nature of the sodium effect indicates SKF 525A to have less opiate agonist character than does methadone. In mice, 2 mg of SKF 525A given intraperitoneally induced less profound analgesia on a hot plate (44 degrees C) than did 0.1 mg of methadone. Analgesia by SKF 525A was prevented by pretreatment of the mice with naloxone. In rats, 50 microgram of SKF 525A given intracerebroventricularly was analgesic.

Lack of parallelism between microsomal enzyme induction and phenobarbital-induced hypercholeresis in the rat.

The relationship between microsomal enzyme induction and the increase in bile flow associated with phenobarbital administration was studied in rats in three experimental situations: examination of the time-course effect of a single dose of phenobarbital (8 mg/100 g body weight) on bile flow and hepatic cytochrome P-450 concentration; study of the influence of SKF 525-A (8 mg/100 g body weight) and cobaltous chloride (6 mg/100 g body weight/day for 3 days) on the phenobarbital-induced hypercholeresis. It was observed that: (a) the maximal increase in bile flow occurred 18 h after the single injection of phenobarbital, while the maximal increase in cytochrome P-450 occurred at 48 h; (b) in rats pretreated with phenobarbital for 3 days, SKF 525-A did not suppress the hypercholeresis due to phenobarbital, and (c) in rats treated with phenobarbital and cobaltous chloride, cytochrome P-450 concentration in the liver was not increased, while bile flow was increased to approximately the same extent as in animals treated with phenobarbital alone. These results further support the hypothesis that microsomal cytochrome P-450-dependent enzyme induction and increase in bile flow are two separate effects of phenobarbital.