Nizoral
Kinetic characterization and identification of the enzymes responsible for the hepatic biotransformation of adinazolam and N-desmethyladinazolam in man.

Venkatakrishnan K, von Moltke LL, Duan SX, Fleishaker JC, Shader RI, Greenblatt DJ.

Department of Pharmacology and Experimental Therapeutics, Tufts University School of Medicine, Boston, MA 02111, USA.

The kinetics of the N-demethylation of adinazolam to N-desmethyladinazolam (NDMAD), and of NDMAD to didesmethyladinazolam (DDMAD), were studied with human liver microsomes using substrate concentrations in the range 10-1000 microM. The specific cytochrome P450 (CYP) isoforms mediating the biotransformations were identified using microsomes containing specific recombinant CYP isozymes expressed in human lymphoblastoid cells, and by the use of CYP isoform-selective chemical inhibitors. Adinazolam was demethylated by human liver microsomes to NDMAD, and NDMAD was demethylated to DDMAD; the substrate concentrations, Km, at which the reaction velocities were 50% of the maximum were 92 and 259 microM, respectively. Another metabolite of yet undetermined identity (U) was also formed from NDMAD (Km 498 microM). Adinazolam was demethylated by cDNA-expressed CYP 2C19 (Km 39 microM) and CYP 3A4 (Km 83 microM); no detectable activity was observed for CYPs 1A2, 2C9, 2D6 and 2E1. Ketoconazole, a relatively specific CYP 3A4 inhibitor, inhibited the reaction; the concentration resulting in 50% of maximum inhibition, IC50, was 0.15 microM and the inhibition constant, Ki, was < 0.04 microM in five of six livers tested. Troleandomycin, a specific inhibitor of CYP 3A4, inhibited adinazolam N-demethylation with an IC50 of 1.96 microM. The CYP 2C19-inhibitor omeprazole resulted in only partial inhibition (IC50 21 microM) and sulphaphenazole, alpha-naphthoflavone, quinidine and diethyldithiocarbamate did not inhibit the reaction. NDMAD was demethylated by cDNA-expressed CYP 3A4 (Km 220 microM, Hill number A 1.21), CYP 2C19 (Km 187 microM, Hill number A 1.29) and CYP 2C9 (Km 1068 microM). Formation of U was catalysed by CYP 3A4 alone. Ketoconazole strongly inhibited NDMAD demethylation (IC50 0.14 microM) and formation of U (IC50 < 0.1 microM) whereas omeprazole and sulphaphenazole had no effect on reaction rates. These results show that CYP 3A4 is the primary hepatic CYP isoform mediating the N-demethylation of adinazolam and NDMAD. Co-administration of adinazolam with CYP 3A4 inhibitors such as ketoconazole or erythromycin might lead to reduced efficacy, since adinazolam by itself has relatively weak benzodiazepine agonist activity, with much of the pharmacological activity of adinazolam being attributable to its active metabolite NDMAD.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9600717&dopt=Abstract ketoconazole Nizoral



Nizoral
[Effect of imidazole antifungal agents on colony formation by murine bone marrow CFUc (colony forming units in culture]

[Article in Hungarian]

Benko I, Megyeri A, Hernadi F, Kovacs P.

Debreceni Orvostudomanyi Egyetem, Gyogyszertani Intezete, Debrecen.

In spite of modern antifungal therapy, the prognosis of systemic mycoses in neutropenic patients is usually poor without recovery of neutrophil counts. So, even a minor myelotoxicity might be a significant disadvantage of any drug used for the treatment of neutropenic patients with fungal infections. Since "Colony Forming Units in culture" (CFUc), the common progenitors of granulocytes and macrophages, are supposed to be a major target of agents damaging bone marrow, we studied the inhibitory effect of four imidazole antifungal drugs to colony formation by murine CFUc in vitro. Clotrimazole, econazole, miconazole or ketoconazole were added to soft agar bone marrow cell cultures at final concentrations of 1 to 30 mg/l at the beginning of the 7 day culture period. A dose-dependent inhibitory effect on colony formation by CFUc was observed with all imidazole drugs studied. The 50 percent inhibitory concentrations (IC50s) were 3.54 mg/l for clotrimazole, 8.07 mg/l for econazole, 14.04 mg/l for miconazole, and 16.11 mg/l for ketoconazole. Human pharmacokinetic data available in the literature on these drugs may help to assess the potential in vivo relevance of our results. The serum levels of clotrimazole and econazole, even after oral administration, remain lower than those found to inhibit colony formation by murine bone marrow in our experiments. Taking into consideration that clotrimazole and econazole are used only topically in the clinical practice, our data do not suggest any clinically significant suppression of bone marrow by these two drugs. Intravenous administration of high doses of miconazole, however, may result in serum concentrations approaching the IC50 for colony formation by murine bone marrow cells in vitro. As for ketoconazole, it may suppress the proliferation of murine bone marrow progenitor cells in vitro at concentrations produced in vivo by high doses (12.5-18 and 30-50 mg/l after 400 or 600 mg, respectively). The serum levels produced by a daily dose of 200 mg ketoconazole (about 4 mg/l), however, did not reduce significantly the number of colonies in murine bone marrow cultures. Our present results warrant further studies of the myelotoxicity of miconazole and ketoconazole in vivo in mice with neutropenia induced by cytostatic agents.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9604489&dopt=Abstract ketoconazole Nizoral



Nizoral
A questionnaire study on the management of onychomycosis: a Canadian perspective.

Gupta AK, Shear NH.

Department of Medicine, Sunnybrook Health Science Center, Toronto, Canada. agupta execulink.com

BACKGROUND: Onychomycosis of the toenails is a condition that responds poorly to griseofulvin. The introduction of terbinafine in Canada in May 1993 resulted in a marked shift in the choice of treatment for pedal onychomycosis. METHODS: A questionnaire survey was carried out in 1996 among Canadian dermatologists regarding the management of onychomycosis. RESULTS: There were 160 respondents from the roughly 350 practicing dermatologists. The dermatologists saw 8 +/- 0.6 patients per week (average +/- standard error (SE) with suspected or diagnosed onychomycosis, with 5 +/- 0.5 patients per week consulting the dermatologists for the first time. Most dermatologists performed mycological testing prior to starting treatment for onychomycosis. The management options for onychomycosis (mean +/- SE) were oral systemic antifungal therapy 51 +/- 3%, no therapy 31 +/- 3%, and nondrug therapy 9 +/- 2%. The majority of dermatologists (83%) used terbinafine as first-line therapy if, indeed, they used oral antifungal agents. In contrast, griseofulvin and ketoconazole were used as first-line therapy in 5% and 1% of cases, respectively. In Canada, there are no monitoring requirements when using oral terbinafine for onychomycosis. Therefore, it is not surprising that only 30% of dermatologists performed monitoring with terbinafine. In contrast, the frequency of monitoring with griseofulvin and ketoconazole was 40% and 80%, respectively. The subset of dermatologists who reported monitoring carried it out in only a fraction of their patients: 47%, 53% and 83% for terbinafine, griseofulvin, and ketoconazole, respectively. Therefore, the overall number of patients in whom regular monitoring was performed was 14.1% 21.2%, and 71.4% for terbinafine, griseofulvin, and ketoconazole, respectively. The perceived cure rates with terbinafine and griseofulvin (mean +/- SE) were 83.7 +/- 1% and 41 +/- 3.1%, respectively. CONCLUSIONS: In May 1996, within three years of the introduction of terbinafine to Canada, this agent has become the drug of choice for the treatment of pedal onychomycosis (at the time of the survey neither itraconazole or fluconazole were approved for onychomycosis). Terbinafine has been found to be very effective and safe, and only a minority of dermatologists perform regular monitoring with this drug.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9646138&dopt=Abstract ketoconazole Nizoral



Nizoral
Effects of ketoconazole on digoxin absorption and disposition in rat.

Salphati L, Benet LZ.

Department of Biopharmaceutical Sciences, School of Pharmacy, University of California at San Francisco, 94143-0446, USA.

Digoxin, a cardiac glycoside, is a substrate of the multidrug transporter P-glycoprotein (Pgp), and in rats has also been identified as a substrate for cytochrome P450 3A (CYP3A). Ketoconazole, an antifungal agent, was shown to inhibit Pgp in a multidrug-resistant cell line, and is known to be a potent inhibitor of CYP3A. Here, we determined the effects of ketoconazole on digoxin absorption and disposition in rats. Digoxin was administered intravenously or orally with or without a concomitant oral dose of ketoconazole. When given intravenously, digoxin AUC increased from 93 +/- 22 to 486 +/- 26 microg x h/l with ketoconazole administration. Similarly, ketoconazole raised the AUC of orally administered digoxin from 63 +/- 17 to 411 +/- 50 microg x h/l. Concomitant ketoconazole administration prolonged digoxin elimination, yielding a nonlinear pharmacokinetic profile. Using time-averaged values, digoxin bioavailability increased from 0.68 +/- 0.18 to 0.84 +/- 0.10, while mean absorption time was reduced from 1.1 +/- 0.4 to 0.3 +/- 0.1 h. Thus, in rats, ketoconazole increases digoxin plasma concentrations, rate of absorption and bioavailability. Although the effects of ketoconazole on AUC could be explained by inhibition of both CYP3A and Pgp, which cannot be differentiated in this study, the decreased mean absorption time can only be explained by inhibition of Pgp in the intestine.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9654217&dopt=Abstract ketoconazole Nizoral



Nizoral
NADPH cytochrome P-450 oxidoreductase and susceptibility to ketoconazole.

Venkateswarlu K, Kelly DE, Manning NJ, Kelly SL.

Institute of Biological Sciences, University of Wales Aberystwyth, Ceredigion, United Kingdom.

The phenotype of a strain of Saccharomyces cerevisiae containing a disruption of the gene encoding NADPH cytochrome P-450 oxidoreductase (CPR) was quantified biochemically and microbiologically, as were those of various transformants of this strain after expression of native CPR, cytochrome P-45051 (CYP51), and a fusion protein of CYP51-CPR (FUS). Only a 4-fold decrease in ergosterol biosynthesis was observed for the cpr strain, but ketoconazole sensitivity increased 200-fold, indicating hypersensitivity to the alternative electron donor system in cpr strains. Both phenotypes could be reversed in transformants expressing the CPR and FUS, indicating the availability of the CPR in FUS as well as the expressed native CPR for monoxygenase-associated reactions. The complementation of function was observed both in vitro and in vivo for the monoxygenases squalene epoxidase, CYP51, and CYP61 in the ergosterol biosynthesis pathway with which CPR is coupled. Overexpression of CYP51 and FUS produced different levels of ketoconazole resistance in wild-type cells, indicating that the availability of CPR may limit the potential of overproduction of CYP51 as a mechanism of resistance to azole antifungal agents.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9661017&dopt=Abstract ketoconazole Nizoral



Nizoral
Antiproliferative effects and mechanism of action of SCH 56592 against Trypanosoma (Schizotrypanum) cruzi: in vitro and in vivo studies.

Urbina JA, Payares G, Contreras LM, Liendo A, Sanoja C, Molina J, Piras M, Piras R, Perez N, Wincker P, Loebenberg D.

Laboratorio de Quimica Biologica, Instituto Venezolano de Investigaciones Cientificas, Caracas, Venezuela. jaurbina churchill.scs.uiuc.edu

We have investigated the antiproliferative effects of SCH 56592, a new experimental triazole, against Trypanosoma (Schizotrypanum) cruzi, the etiological agent of Chagas' disease in Latin America. SCH 56592 blocked the proliferation of the epimastigote form of the parasite in vitro at 30 nM, a concentration 30- to 100-fold lower than that required with the reference compounds ketoconazole and itraconazole. At that concentration all the parasite's endogenous sterols (ergosterol, 24-ethyl-cholesta-5,7,22-trien-3 beta-ol, and its 22-dihydro analogs), were replaced by methylated sterols (lanosterol and 24-methylene-dihydrolanosterol), as revealed by high-resolution gas chromatography coupled with mass spectrometry. This indicated that the primary mechanism of action of the drug was inhibition of the parasite's sterol C-14 alpha demethylase. Against the clinically relevant intracellular amastigote form, grown in cultured Vero cells at 37 degrees C, the MIC of SCH 56592 was 0.3 nM, again 33- to 100-fold lower than that of ketoconazole or itraconazole. In a murine model of acute Chagas' disease, SCH 56592 given at > or = 10 mg/kg of body weight/day for a total of 43 doses allowed 85 to 100% survival and 90 to 100% cure of the surviving animals, as verified by parasitological, serological, and PCR-based tests, while ketoconazole given at 30 mg/kg day allowed 60% survival but only 20% cure. In a murine model of chronic Chagas' disease, SCH 56592 was again more effective than ketoconazole, providing 75 to 85% protection from death, with 60 to 75% parasitological cures of the surviving animals, while no parasitological cures were observed with ketoconazole. The results indicate that SCH 56592 is the most powerful sterol biosynthesis inhibitor ever tested against T. cruzi and may be useful in the treatment of human Chagas' disease.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9661019&dopt=Abstract ketoconazole Nizoral



Nizoral
Effects of ketoconazole on ovulatory changes in the rat: implications on the role of a meiosis-activating sterol.

Tsafriri A, Popliker M, Nahum R, Beyth Y.

Department of Biological Regulation, The Weizmann Institute of Science, Rehovot, Israel.

In-vitro studies on mouse oocytes have shown that human follicular fluid and bull testes contain an activity which partially overrides the inhibitory action of hypoxanthine on meiosis. This activity was ascribed to two closely related sterols, subsequently named meiosis-activating sterols (MAS). We have used a potent inhibitor of sterol synthesis, ketoconazole, in order to test in vivo and in vitro whether MAS play a necessary physiological role in the resumption of meiosis in the rat. When administered systemically, ketoconazole (8.3-16.6 mg/rat) suppressed ovulation by 40%. Local unilateral administration of the drug into the ovarian bursa (1.25 mg/bursa) resulted in 75% inhibition of ovulation in comparison with the contralateral ovary. All the ovulated ova in the oviduct were mature. Histological examination of the ketoconazole-treated ovaries revealed mature oocytes trapped in follicles which failed to ovulate. Furthermore, extraction of oocytes from the large follicles of such ovaries revealed that 79% of them were mature. Addition of ketoconazole (0.0001-0.01 mM) to the culture medium did not affect significantly the spontaneous maturation of rat oocytes. However, ketoconazole at a higher concentration (0.1 mM) caused the degeneration of oocytes. Ketoconazole (0.01 mM) did not affect luteinizing hormone (LH)-stimulated oocyte maturation in explanted preovulatory follicles, even though it inhibited follicular progesterone production to levels below the hormone-free control follicles. At higher levels, ketoconazole caused the degeneration of follicles and the enclosed oocytes. In conclusion, using a potent inhibitor of MAS we have failed to confirm the suggested obligatory role of MAS in the resumption of meiosis in the rat both in vivo and in vitro.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9665635&dopt=Abstract ketoconazole Nizoral