Griseofulvin Radiosensitizes Non-Small Cell Lung Cancer Cells and Activates cGAS

Extra copies of centrosomes are frequently observed in cancer cells. To survive and proliferate, cancer cells have developed strategies to cluster extra-centrosomes to form bipolar mitotic spindles. The aim of this study was to investigate whether centrosome clustering (CC) inhibition (CCi) would preferentially radiosensitize non-small cell lung cancer (NSCLC). Griseofulvin (GF; FDA-approved treatment) inhibits CC, and combined with radiation treatment (RT), resulted in a significant increase in the number of NSCLC cells with multipolar spindles, and decreased cell viability and colony formation ability in vitro. In vivo, GF treatment was well tolerated by mice, and the combined therapy of GF and radiation treatment resulted in a significant tumor growth delay. Both GF and radiation treatment also induced the generation of micronuclei (MN) in vitro and in vivo and activated cyclic GMP-AMP synthase (cGAS) in NSCLC cells. A significant increase in downstream cGAS-STING pathway activation was seen after combination treatment in A549 radioresistant cells that was dependent on cGAS. In conclusion, GF increased radiation treatment efficacy in lung cancer preclinical models in vitro and in vivo. This effect may be associated with the generation of MN and the activation of cGAS. These data suggest that the combination therapy of CCi, radiation treatment, and immunotherapy could be a promising strategy to treat NSCLC.

Biological and Chemical Control of Sclerotinia sclerotiorum using Stachybotrys levispora and Its Secondary Metabolite Griseofulvin

Sclerotinia sclerotiorum is responsible for the white mold of soybeans, and the difficulty to control the disease in Brazil is causing million-dollar damages. Stachybotrys levispora has shown activity against S. sclerotiorum. In our present investigation, we analyzed the chemical basis of this inhibition. Eight compounds were isolated, and using spectroscopic methods, we identified their structures as the known substances 7-dechlorogriseofulvin, 7-dechlorodehydrogriseofulvin, griseofulvin, dehydrogriseofulvin, 3,13-dihydroxy-5,9,11-trimethoxy-1-methylbenzophenone, griseophenone A, 13-hydroxy-3,5,9,11-tetramethoxy-1-methylbenzophenone, and 12-chloro-13-hydroxy-3,5,9,11-tetramethoxy-1-methylbenzophenone. Griseofulvin inhibited the mycelial growth of S. sclerotiorum at 2 μg mL-1. Thus, the antagonistic effect of S. levispora to S. sclerotiorum may well be due to the presence of griseofulvins. Our results stimulate new work on the biosynthesis of griseofulvins, to locate genes that encode key enzymes in these routes and use them to increase the production of these compounds and thus potentiate the fungicide effect of this fungus. S. levispora represents an agent for biocontrol, and griseofulvin represents a fungicide to S. sclerotiorum.

Exploring the binding sites and binding mechanism for hydrotrope encapsulated griseofulvin drug on γ-tubulin protein

The protein γ-tubulin plays an important role in centrosomal clustering and this makes it an attractive therapeutic target for treating cancers. Griseofulvin, an antifungal drug, has recently been used to inhibit proliferation of various types of cancer cells. It can also affect the microtubule dynamics by targeting the γ-tubulin protein. So far, the binding pockets of γ-tubulin protein are not properly identified and the exact mechanism by which the drug binds to it is an area of intense speculation and research. The aim of the present study is to investigate the binding mechanism and binding affinity of griseofulvin on γ-tubulin protein using classical molecular dynamics simulations. Since the drug griseofulvin is sparingly soluble in water, here we also present a promising approach for formulating and achieving delivery of hydrophobic griseofulvin drug via hydrotrope sodium cumene sulfonate (SCS) cluster. We observe that the binding pockets of γ-tubulin protein are mainly formed by the H8, H9 helices and S7, S8, S14 strands and the hydrophobic interactions between the drug and γ-tubulin protein drive the binding process. The release of the drug griseofulvin from the SCS cluster is confirmed by the coordination number analysis. We also find hydrotrope-induced alteration of the binding sites of γ-tubulin protein and the weakening of the drug-protein interactions.

qNMR for profiling the production of fungal secondary metabolites

Analysis of complex mixtures is a common challenge in natural products research. Quantitative nuclear magnetic resonance spectroscopy offers analysis of complex mixtures at early stages and with benefits that are orthogonal to more common methods of quantitation, including ultraviolet absorption spectroscopy and mass spectrometry. Several experiments were conducted to construct a methodology for use in analysis of extracts of fungal cultures. A broadly applicable method was sought for analysis of both pure and complex samples through use of an externally calibrated method. This method has the benefit of not contaminating valuable samples with the calibrant, and it passed scrutiny for line fitting and reproducibility. The method was implemented to measure the yield of griseofulvin and dechlorogriseofulvin from three fungal isolates. An isolate of Xylaria cubensis (coded MSX48662) was found to biosynthesize griseofulvin in the greatest yield, 149 ± 8 mg per fermentation, and was selected for further supply experiments. Copyright © 2016 John Wiley & Sons, Ltd.

Probing adsorption of DSPE-PEG2000 and DSPE-PEG5000 to the surface of felodipine and griseofulvin nanocrystals

Nanosized formulations of poorly water-soluble drugs show great potential due to improved bioavailability. In order to retain colloidal stability, the nanocrystals need to be stabilized. Here we explore the use of the poly(ethylene glycol) (PEG) conjugated phospholipids DSPE-PEG2000 and DSPE-PEG5000 as stabilizers of felodipine and griseofulvin nanocrystals. Nanocrystal stability and physicochemical properties were examined and the interaction between the PEGylated lipids and the nanocrystal surface as well as a macroscopic model surface was investigated. Using quartz crystal microbalance with dissipation monitoring both mass adsorption and the thickness of the adsorbed layer were estimated. The results indicate that the PEGylated lipids are adsorbed as flat layers of around 1-3nm, and that DSPE-PEG5000 forms a thicker layer compared with DSPE-PEG2000. In addition, the mass adsorption to the drug crystals and the model surface are seemingly comparable. Furthermore, both DSPE-PEG2000 and DSPE-PEG5000 rendered stable drug nanocrystals, with a somewhat higher surface binding and stability seen for DSPE-PEG2000. These results suggest DSPE-PEG2000 and DSPE-PEG5000 as efficient nanocrystal stabilizers, with DSPE-PEG2000 giving a somewhat higher surface coverage and superior colloidal stability, whereas DSPE-PEG5000 shows a more extended structure that may have advantages for prolongation of circulation time in vivo and facilitation for targeting modifications.

Metabolite profiling using liquid chromatography/quadrupole time-of-flight mass spectrometry for the identification of a suitable marker and target matrix of griseofulvin use in bovines

RATIONALE

Griseofulvin is an antifungal agent with potential for misuse in food-producing animals. Little is known about its metabolism in ruminants and hence what are suitable marker residues and target matrices for monitoring purposes.

METHODS

Tissues harvested from cattle treated with the antifungal agent griseofulvin were screened using liquid chromatography coupled to positive and negative electrospray ionization (ESI) quadrupole time-of-flight mass spectrometry (qToFMS) operated in ToF mode.

RESULTS

Twenty-five possible metabolites were detected across all tissue types, but two isomeric compounds with accurate masses corresponding to loss of a methyl group from parent griseofulvin were considered to be the best candidate markers. Data from fragmentation experiments enabled a tentative assignment of the structures of the two compounds as 4-demethylgriseofulvin and 6-demethylgriseofulvin. These assignments were confirmed by matching the product ion spectra of incurred residues to those of custom synthesized reference standards.

CONCLUSIONS

4-Demethyl- and 6-demethylgriseofulvin have been identified as potential marker compounds of griseofulvin use in cattle. Liver was identified as the target matrix. Hair was shown to have potential for non-invasive testing.

Absorption and Elimination of Griseofulvin from the Alimentary Tract of the Rat

A new method is described for determining griseofulvin in the alimentary canal of rats dosed orally with the antibiotic: slightly modified, the method was used for measuring faecal griseofulvin. Attempts have been made to correlate the appearance of griseofulvin in the blood stream with its disappearance from the alimentary canal and to assess how much of a single oral dose is absorbed. Lack of griseofulvin at its main absorption sites in the alimentary tract was not responsible for the decline in blood level 4 hr. after oral dosing, because substantial amounts of unabsorbed antibiotic were then still present. Faecal elimination of griseofulvin, as determined by the new assay, is much greater than reported earlier.

The Influence of Sex on the Catabolism of Griseofulvin

Blood griseofulvin levels have been determined on rats given a single oral, subcutaneous, intraperitoneal or intravenous dose and on guinea pigs and human volunteers after oral administration. In rats the blood levels of females were higher than those of males: this applied to all four routes of administration. No differences in blood levels between males and females were observed in guinea pigs or human volunteers. In vitro studies have shown that liver slices obtained from male rats destroy griseofulvin more rapidly than those from females; the sex difference did not apply to rabbits or guinea pigs.

Prediction of oral absorption of griseofulvin, a BCS class II drug, based on GITA model: Utilization of a more suitable medium for in-vitro dissolution study

The in-vivo absorbability of drugs categorized into the biopharmaceutics classification system (BCS) class II is very difficult to be predicted because of the large variability in the absorption and/or dissolution kinetics and the lack of an adequate in-vitro system for evaluating the dissolution behavior. We tried to predict the in-vivo absorption kinetics of griseofulvin, categorized into BCS class II, orally administrated as powders into rats, based on Gastrointestinal-Transit-Absorption model (GITA model), consisting of the absorption, dissolution and GI-transit processes. Using the dissolution rate constants (k(dis)) of griseofulvin obtained with JP 1st solution, JP 2nd solution, FaSSIF, FeSSIF and modified SIBLM as a medium, simulation lines were not able to describe the observed mean plasma profile at all. On the other hand, a calculated line provided by employing k(dis) obtained with MREVID 2 (medium reflecting in-vivo dissolution 2), a new medium, was in better agreement with the observed mean plasma profile than existing media, indicating that the utilization of adequate k(dis) value made it possible to predict the in-vivo absorption kinetics of drugs classified into BCS class II based on GITA model and that MREVID 2 could be a useful medium for describing the in-vivo dissolution kinetics.

Oral absorption of poorly water-soluble drugs: computer simulation of fraction absorbed in humans from a miniscale dissolution test

PURPOSE

The purpose of this study was to develop a new system for computer simulation to predict fraction absorbed (F(a)) of Biopharmaceutical Classification System (BCS) class II (low solubility-high permeability) drugs after oral administration to humans, from a miniscale dissolution test.

METHODS

Human oral absorption of 12 lipophilic drugs was simulated theoretically by using the dissolution and permeation parameters of the drugs. A miniscale dissolution test and a solubility study were carried out in a conventional buffer and a biorelevant medium (pH 6.5). A dissolution parameter, which can simulate in vivo dissolution, was obtained from the in vitro dissolution curve. Human intestinal permeability was estimated assuming that the permeation was limited by diffusion through the unstirred water layer. The F(a) in humans was predicted and then compared with clinical data.

RESULTS

The dissolution and solubility of most model drugs were faster and higher in a biorelevant medium than in a conventional buffer. The simulated absorption was limited by the drug dissolution rate and/or solubility. Predicted F(a) was significantly correlated with clinical data (correlation coefficient r2 = 0.82, p < 0.001) when the dissolution profiles in biorelevant medium were used for the simulation.

CONCLUSIONS

This new system quantitatively simulated human absorption and would be beneficial for the prediction of human F(a) values for BCS class II drugs.

Synthesis and Enhancing Effect of Transkarbam 12 on the Transdermal Delivery of Theophylline, Clotrimazole, Flobufen, and Griseofulvin

PURPOSE

Dodecyl-6-aminohexanoate (DDEAC) is a transdermal permeation enhancer with excellent activity, low toxicity, and no dermal irritation. We hypothesized that DDEAC reacts with air CO2 to form a two-chain ammonium carbamate--Transkarbam 12 (T12)--which is responsible for the enhancing effect.

METHODS

DDEAC and T12 were synthesized, their structures were confirmed by spectral methods, and their enhancing activity was studied using the Franz diffusion cell and human skin. A high-performance liquid chromatography method was developed for determination of T12, and its biodegradability was evaluated using porcine esterase.

RESULTS

Only the carbamate salt T12 was responsible for the high enhancing activity; DDEAC tested under argon to avoid reaction with CO2 was inactive. T12 enhanced transdermal permeation of drugs covering a wide range of physicochemical properties, including theophylline (enhancement ratio up to 55.6), clotrimazole (7.7), flobufen (5.0), and griseofulvin (24). The activity was pH-dependent, further confirming the importance of the carbamate structure. The metabolization of T12 followed a second-order kinetics with t(1/2) = 31 min.

CONCLUSION

Our results indicate that T12 is a promising biodegradable permeation enhancer for a wide range of drugs, and the structurally novel group of carbamate enhancers warrants further investigation.

Detection of griseofulvin in a marine strain of Penicillium waksmanii by ion trap mass spectrometry

A marine strain of Penicillium waksmanii Zaleski was isolated from a sample of seawater from shellfish-farming area in the Loire estuary (France). The in vitro marine culture showed an important antifungal activity. Bioassay-guided fractionation was used to purify the crude extract. Dereplication by electrospray-ion trap/mass spectrometry (ESI-IT/MS) afforded the identification of the antifungal compound, after a semi-purification consisting of two stages. A comparison of the ionic composition between the active and the non-active fractions allowed the detection of a monocharged ion at m/z 353 containing a chlorine atom, which could be attributed to the antifungal griseofulvin [C17H17ClO6+H]+. Multi-stage fragmentation (MSn) confirmed the identity of the m/z 353 ion of the antifungal fraction as griseofulvin. It is the first description of griseofulvin production by a strain of P. waksmanii and the first chemical study of a strain of this species isolated from marine temperate cold water.

Formation of Mallory body-like inclusions and cell death induced by deregulated expression of keratin 18

Mallory bodies (MBs) are cytoplasmic inclusions that contain keratin 8 (K8) and K18 and are present in hepatocytes of individuals with alcoholic liver disease, nonalcoholic steatohepatitis, or benign or malignant hepatocellular neoplasia. Mice fed long term with griseofulvin are an animal model of MB formation. However, the lack of a cellular model has impeded understanding of the molecular mechanism of this process. Culture of HepG2 cells with griseofulvin has now been shown to induce both the formation of intracellular aggregates containing K18 as well as an increase in the abundance of K18 mRNA. Overexpression of K18 in HepG2, HeLa, or COS-7 cells also induced the formation of intracellular aggregates that stained with antibodies to ubiquitin and with rhodamine B (characteristics of MBs formed in vivo), eventually leading to cell death. The MB-like aggregates were deposited around centrosomes and disrupted the microtubular array. Coexpression of K8 with K18 restored the normal fibrous pattern of keratin distribution and reduced the toxicity of K18. In contrast, an NH(2)-terminal deletion mutant of K8 promoted the formation of intracellular aggregates even in the absence of K18 overexpression. Deregulated expression of K18, or an imbalance between K8 and K18, may thus be an important determinant of MB formation, which compromises the function of centrosomes and the microtubule network and leads to cell death.

[Biosynthesis and microbial transformation of griseofulvin and carcinogenesis and prevention of cancer by estrogens]

In the biosynthetic study of griseofulvin by Penicillium urticae and microbial transformation of (-)- and (+)-dehydrogriseofulvin and their derivatives by Streptomyces cinereocrocatus excellent informations were obtained from 2H-NMR spectroscopy. In the reduction of (-)-dehydrogriseofulvin into (+)-griseofulvin by a partially purified enzyme system of S. cinereocrocatus, the origin of the 6' alpha-hydrogen of (+)-griseofulvin was a hydride ion donated by pro-4R-hydrogen of NADPH. In connection with the study of carcinogenesis, diethylstilbestrol (DES) was proved to disrupt microtubules in vitro. The other synthetic estrogens, E,E-dienestrol, meso-hexestrol, and dl-hexestrol were inhibitors of microtubule assembly in vitro, and induced twisted ribbon structures or ribbon-sheet-microtubules from microtubule proteins. Next, the effects of DES and its methyl ethers on the chromosome of and the cellular microtubule architecture, revealed by fluorescent anti-tubulin antibody, of Chinese hamster V79 cells were examined, and further estradiol-17 beta was proved to exhibit higher microtubule-disruptive activity than DES in V79 cells. Furthermore, cytoplasmic microtubules in the human breast cancer cell lines MCF-7 and MDA-MB-231, estrogen receptor-positive and -negative cell lines, respectively, were disrupted equally by estradiol-17 beta. Then, natural estrogens and their derivatives comprising 30 compounds in total were tested in Chinese hamster V79 cells, proving that 2-methoxyestradiol showed the strongest activity (EC50: 2 microM) to disrupt microtubules. Further, in the assay of indenestrol A, a metabolite of DES, indenestrol B and their monomethyl ethers, the 4'-methyl ether of [(-)-3S]-indenestrol B exhibited both the strongest cytotoxicity in, and greatest disruption of the cellular microtubules of V79 cells, and no correlation with the affinity for estrogen receptors was shown.

Antifungal therapy: potential interactions with other classes of drugs

Combination drug therapy is widely used for the management of many common medical conditions. The concurrent use of more than one drug can significantly alter the therapeutic and side-effect profile of each individual agent. Such drug-drug interactions are generally classified either as pharmacokinetic or pharmacodynamic. Oral agents used for the management of superficial fungal infections can have both types of interactions. This article describes common drug-drug interactions observed with amphotericin B, flucytosine, griseofulvin, ketoconazole, fluconazole, and itraconazole.

Labelling in vivo and chirality of griseofulvin-derived N-alkylated protoporphyrins

1. We have compared the response to griseofulvin of rats and mice and, in mice, the effect of griseofulvin itself with that of two of its analogues. The severity of protoporphyria shows a correlation with the accumulation of both types of N-alkylated porphyrins previously described after treatment with this drug, namely N-methylproptoporphyrin and the N-griseofulvin protoporphyrin adduct. 2. Both N-alkylporphyrins are chiral, are labelled from 5-amino[4-14C]laevulinate, and their liver accumulation can be inhibited by pretreatment with a suicide substrate of cytochrome P-450, which also prevents porphyria. 3. These findings suggest that cytochrome P-450 is involved in the mechanism of griseofulvin-induced protoporphyria by generating N-methylprotoporphyrin. The N-griseofulvin protoporphyrin adduct may also originate from cytochrome P-450, but more work is necessary to elucidate whether it acts as the precursor for N-methylprotoporphyrin.

Drug binding and solubility in milk

The binding and solubility of nitrofurantoin, piroxicam, indomethacin, prednisolone, diazepam, dicumarol, and griseofulvin in milk were determined at 15, 25, and 37 degrees C in bovine milk samples with fat contents of 0.75 and 3.50%. Drug binding to milk components was independent of drug concentration over the drug concentration studied, and the fat content of milk strongly affected binding values of most of the listed drugs. Further, drug binding increased with decreasing temperatures for most of the drugs examined. The solubility of all drugs is greatly enhanced in milk compared to their aqueous solubility (pH 6.5 phosphate buffer). The high solubility cannot be accounted for solely on the basis of drug binding to milk components. An attempt is made to correlate the binding and solubility data with physicochemical properties of the drugs (logP, pKa, aqueous solubility). The potential significance of these findings is discussed with regard to preparation and in vivo delivery of drugs from drug-milk formulations.

Regio- and stereoselective hydrogenation of 2'-demethoxy-2'-methyldehydrogriseofulvin, a symmetrical substrate, to (+)-2'-demethoxy-2'-methylgriseofulvin with a cell-free system of Streptomyces cinereocrocatus

Enzymatic hydrogenation of 2'-demethoxy-2'-methyldehydrogriseofulvin (5) with a cell-free system of Streptomyces cinereocrocatus afforded (+)-2'-demethoxy-2'-methylgriseofulvin (6). The structure of 6 was determined on the basis of comparisons of the proton nuclear magnetic resonance spectrum, mass spectrum, and circular dichroism with those of a standard specimen which was synthesized chemically. The results demonstrated that when the 2'-position of (-)-dehydrogriseofulvin was substituted with a methyl group, its hydrogenation with the cell-free system occurred stereoselectively at the 5',6'-position.

Pharmacokinetics of griseofulvin in blood and skin suction blister fluid of rats

The penetration of griseofulvin to its site of action was investigated in the rat using subepidermal blisters induced by suction as a model. Griseofulvin was administered iv at a dose of 20 mg/kg after which blood, suction blister fluid (SBF), and skin tissue were sampled over a 300-min time period. The blood level/time course can be described by a two-compartment model. During the terminal phase, concentrations of drug in blood, SBF, and cutis declined in parallel, with respective half-lives of 71.0, 70.4, and 74.6 min. In SBF, maximum concentrations (2.35 +/- 0.36 micrograms/ml) were obtained 60 min postinjection, drug levels increased until the concentrations of unbound griseofulvin in SBF and plasma were identical. Time to peak concentration in cutis was shorter (20 min; 13.9 +/- 0.5 micrograms/ml). As the dermatophytes are located in the horny layer, the determination of griseofulvin in SBF seems to be a more suitable assay for determining the griseofulvin level profile at its site of action. In addition, the level of unbound, and thus active, griseofulvin in SBF was severalfold lower than the concentration of total drug in excised skin tissue. Up to now, the latter value has been considered to indicate that the concentration of griseofulvin in the skin is comparable to the in vitro sensitivity of dermatophytes. The present results show that this seems to be no longer justified.

Influence of bile salts and lipids on intestinal absorption of griseofulvin in man

The influence of bile salts and lipids on the intestinal absorption of griseofulvin has been studied in 11 healthy male volunteers by the intestinal perfusion technique. The drug in a nutrient solution (Realmentyl) was perfused into the second part of duodenum at 5 ml/min. Intestinal samples were taken continuously at 1 ml/min, 20 cm (at the angle of Treitz) and 45 cm distal to the perfusion point. To study the effect of lipids on griseofulvin absorption, the drug was perfused with solutions A and B, of which B contained a total lipid and caloric load three times that of A. The influence of bile salts on griseofulvin absorption was examined by perfusing the drug on Day 1 with bile salts and again on the following day after bile salt depletion. Bile salts and a varying quantity of lipid perfusate had no significant influence on the duodeno-jejunal griseofulvin absorption rate per cm of intestine. Lipids, however, may still play a role in griseofulvin absorption along the entire intestine.

Analysis of drug-tubulin interaction by trypsin cleavage: comparison for colchicine, podophyllotoxin, griseofulvin, vinblastine and taxol

Trypsin preferentially cleaves the alpha subunit of depolymerized tubulin or vinblastine induced aggregates (in which longitudinal interactions between tubulin molecules could take place). No cleavage was found for tubulin polymerized into microtubules (containing lateral and longitudinal tubulin interactions), in the presence of taxol. In the presence of colchicine or podophyllotoxin the alpha subunit was partially protected from proteolytic digestion. Trypsin digestion pattern varied upon the addition of different concentrations of griseofulvin. At the higher concentration used, in which microtubules assembly was inhibited, both tubulin subunits were cleaved.

The in vitro liberation and the bioavailability of different brands of griseofulvin in plasma and urine in man

The bioavailability of griseofulvin in three different brands, two microfine forms (Gricin = G, Likuden = L), and one ultramicrofine form (Gris-PEG = GP), was determined in plasma and urine in six healthy volunteers in a crossover study and compared with in vitro liberation data. GP shows a higher AUCo infinity (140 +/- 24 mumol . h . l-1) and Cmax (4.5 +/- 0.1 mumol . h-1) than the microsize brands of griseofulvin (AUCo infinity:58 +/- 7, and 45 +/- 6 mumol . h . l-1; Cmax:1.7 +/- 0.2, and 1.5 +/- 0.2 mumol . l-1; G and L, resp.), but the same tmax at the third hour. There results correspond with the in vitro liberation data. Contradictory results of the bioavailability are found by determining the amount of 6-Demethylgriseofulvin eliminated in urine. The elimination of this main metabolite after dosing with L is lower (0.18 +/- 0.02 mmol) than those of the other two brands, which do not differ (0.31 +/- 0.04; 0.32 +/- 0.02 mmol, G and GP, resp.). It is concluded that the determination of bioavailability only by means of the eliminated amount of a metabolite in urine may produce false results.

Fat contents of meals and bioavailability of griseofulvin in man

The bioavailability of griseofulvin was followed in twelve healthy volunteers by measuring the urinary excretion of the major metabolite 6-demethylgriseolfulvin, after each volunteer had ingested one 500 mg griseofulvin tablet under (1) fasting conditions, (2) immediately after a typical low-fat and (3) high-fat Nigerian meals. An increase of about 70 and 120% absorption occurred with the ingestion of the low-fat and high-fat meals respectively compared to the fasting state (P less than 0.01). The maximum excretion rates of the free metabolite (Vmax.) were also significantly increased (P less than 0.01) following consumption of low and high fat meals. Our results thus suggest that the higher the fat content of the meals the higher the enhancement of the bioavailability of griseofulvin in man.

Species-specific differences in toxicity of antimitotic agents toward cultured mammalian cells

Toxicities of various microtubule inhibitors, namely, colchicine, podophyllotoxin, maytansine, vinblastine, nocodazole, griseofulvin, and steganacine, toward numerous independently established cell lines from three different species, namely, human, mouse, and Chinese hamster, were examined. Some of these inhibitors (namely, colchicine, vinblastine, taxol, and maytansine) were found to exhibit large (between tenfold and fiftyfold) differences in their toxic and antimitotic concentrations toward various cell lines and these differences appeared to be species related inasmuch as all cell lines from a particular species showed similar sensitivities toward these inhibitors. Of the three species examined, cells of human origin exhibited maximum sensitivity toward these inhibitors while Chinese hamster cells were found to be most resistant. The reduced cellular transport of [3H]colchicine and [3H]vinblastine in Chinese hamster cells as compared to the cellular transport in human cells and the equivalent binding of [3H]colchicine and [3H]vinblastine to microtubule proteins in cell extracts from both these lines provided strong evidence that the observed differences in toxicity to these inhibitors were most likely caused by differences in the cellular transport of these drugs. In contrast to the toxicities of the above compounds, the toxicities of other microtubule inhibitors such as podophyllotoxin, steganacine, griseofulvin, and nocodazole were found to be very similar for cells from all three species, indicating that the cellular transport of these 2 groups of microtubule inhibitors differed in some important respect. Some implications of the observed species-specific differences in drug toxicity to clinical studies are discussed.

Human plasma and skin blister fluid levels of griseofulvin after its repeated administration

Griseofulvin was administered orally to 6 healthy volunteers for 6 days. The subjects received 500 mg of a microsize formulation and 330 mg of an ultramicrosize formulation, according to a cross-over design. The drug was determined in plasma, suction blister fluid (SBF) and cantharides blister fluid (CBF) following the last dose. Urinary excretion of the main metabolites 6-demethylgriseofulvin (6-DMG) and its glucuronic acid conjugate was also measured. The pharmacokinetic parameters were compared with those obtained from a recent single dose experiment. On repeated administration, the bioavailability of griseofulvin was significantly lower from the microsize formulation; the urinary recovery of total 6-DMG was 33.8% versus 53.6% on administration of the ultramicrosize material. Bioavailability was reduced as compared to ingestion of a single dose. The reduction was more prominent following the microsize (36%) than the ultramicrosize (17%) formulation. Penetration into skin blister fluid was not altered as compared to the single dose experiment. Relative areas under the blister fluid-time curves amounted to 51% (SBF) and 80% (CBF) of the area under the plasma level-time curve. The concentration of unbound griseofulvin in these body fluids was identical throughout the entire dosage interval. Unbound griseofulvin levels were low in comparison with the minimum inhibitory concentrations for strains of trichophyton and microsporum.

Human plasma and skin blister fluid levels of griseofulvin following a single oral dose

Griseofulvin and 6-demethylgriseofulvin (6-DMG) in plasma, suction blister fluid (SBF) and cantharides blister fluid (CBF) and urinary excretion of 6-DMG, were evaluated following administration of single oral doses of an ultramicrosize and a microsize formulation of griseofulvin to 6 healthy volunteers. The bioavailability of griseofulvin was higher following the ultramicrosize formulation when 64% of the dose was recovered (via metabolites) versus 52% after the microsize preparation. Penetration into skin blister fluid was delayed as compared to plasma levels; the peak concentration in plasma was observed at 3-4 h, whereas griseofulvin in CBF increased up to 6 h. The terminal half-live was calculated from plasma levels to 9.3 h. The half-lives calculated from SBF and CBF concentrations were 9.2 and 9.8 h, respectively, (n = 5). In plasma 84% of griseofulvin was bound to proteins, predominantly to albumin; binding in SBF and CBF was 72 and 82%, respectively. 3 h after drug administration the free concentration in plasma significantly exceeded the free concentrations in SBF and CBF. Distribution equilibrium between plasma and skin blister fluid was observed after 27 h. Thus, during chronic administration, the plasma griseofulvin level should reflect its concentration in the target organ.

Bioavailability of griseofulvin plain tablets in stomach-emptying controlled rabbits and the correlation with bioavailability in humans

Bioavailability after giving oral doses of 62.5 mg griseofulvin tablets having different dissolution rates to stomach-emptying controlled rabbits, was estimated and compared with that in humans receiving 125 mg dose of the same griseofulvin preparations. The relative differences in Cmax and AUC infinity between the product with the highest availability and others tended to be greater in rabbits than in humans. The in vivo parameters correlated well between the two species. However, power analysis indicated a larger variability of Cmax in rabbits than in other species (dogs, minipigs and humans). Water volume (5 and 50 ml) coadministered with the drug did not significantly influence the bioavailability. The rabbits which were not given food after oral dosing with griseofulvin exhibited a lower Cmax than those which were fed immediately after dosing. The bioavailability of an ultramicronized formulation in rabbits was higher after the postprandial dose than after the preprandial dose. Food intake just after the drug administration seems to be an important factor for controlling the passage rate of the drug through the gastrointestinal tract in stomach-emptying controlled rabbits.

The effect of an oral therapeutic single-dose of griseofulvin on polymorphonuclear leukocyte migration in a casein gradient

In a previous study, polymorphonuclear (PMN) leukocyte chemotaxis in vitro was inhibited by therapeutic concentrations of griseofulvin. In the present investigation, PMN migration in a casein gradient was studied in a cell suspension containing serum collected before and after a therapeutic peroral single-dose of griseofulvin. The PMN migration in vitro was not influenced significantly by the presence of griseofulvin-containing serum. It is suggested that peroral griseofulvin treatment has negligible effect on PMN chemotaxis in vitro.

Use of PKM-MULTI program for fitting discontinuous absorption profiles using a microcomputer

The programs for the pharmacokinetic models with discontinuous absorption, written in BASIC, were connected to MULTI, which had been proposed for nonlinear least squares for a microcomputer by Yamaoka et al. Using this program (designated as PKM-MULTI), the same data sets previously calculated by HFCM, FITSI2 and NONLIN were fitted and the finally obtained estimates were in close agreement with those obtained previously. The plasma data of nalidixic acid were also fitted to the pharmacokinetic model with discontinuous absorption, which were suggested to be more valid compared with one compartment model with continuous absorption.

Bioavailability of griseofulvin from plain tablets in Göttingen minipigs and the correlation with bioavailability in humans

Intravenous administration of 125 mg of griseofulvin to G ottingen minipigs showed biexponential elimination of the drug from plasma, in which the half lives of the initial and terminal phases were 0.2-0.6 h and 4.3-6.6 h, respectively. The bioavailability of four griseofulvin tablets used in a human bioavailability study was investigated in the pigs and compared with the human results. The differences of Cmax and AUC between the standard product and the others were smaller in the pig than in humans, however, the correlations of Cmax and AUC between humans and minipigs were high for the four products. The differences of Tmax among the products were small, and the Tmax of the standard product was large in the pigs compared with that in humans. In addition, delayed onset of drug absorption was observed in some of the pigs. The findings suggest slow gastric emptying of the drug in the pigs. The statistically small powers for the in vivo parameters observed in the pig, seem to indicate variable absorption of the drug in the animal.

Use of metzler's NONLIN program for fitting discontinuous absorption profiles

An alternative to the use of integral hybrid flow/compartmental model (HFCM) equations in fitting cases I and II discontinuous absorption profiles is presented. It is proposed that HFCM-integral equations be replaced by a system of differential equations in which sequential sets of equations describe the absorption profile from time zero to infinity. The required sets of differential equations for these two cases are presented as they apply to a two-compartment drug, potentially undergoing multiple absorption steps. It was shown that the use of the NONLIN program in the differential equation mode provides good fits for some unusually shaped absorption profiles of buformin, sulfisoxazole, and griseofulvin. The values of the parameter estimates and the sum of squared deviations, sigma SD, obtained with NONLIN were almost identical to those obtained with the FITS12 program utilizing HFCM equations. While HFCM-integral equations required less computer time, they introduced the potential for negative absorption times. This problem is avoided by use of the differential equations method.

Bioavailability of griseofulvin from tablets in beagle dogs and correlation with dissolution rate and bioavailability in humans

The bioavailability of four griseofulvin tablets in beagle dogs, including an ultramicrosize tablet used previously in a human bioavailability study, was investigated on the basis of the plasma 6-demethyl-griseofulvin concentration. The relations with the in vivo findings in humans and the in vitro dissolution rates also were examined. Contrary to the lower bioavailability of the ultramicrosize formulation in humans, it provided the best bioavailability in beagles. The microsize griseofulvin formulations showed similar in vivo results to those in humans. Poor correlation of in vivo parameters between humans and beagles was attributed to the discrepancy of the availability of the ultramicrosize formulation between the two species. The dissolution rates determined by the pretreatment method using plastic beads were correlated more with the in vivo findings than those determined by the other methods. Beagles were a useful animal model for bioavailability studies of certain griseofulvin formulations but not ultramicrosize ones.

Bioavailability of griseofulvin from tablets in humans and the correlation with its dissolution rate

Dissolution rates of 10 commercial microsize griseofulvin tablets and one ultramicrosize griseofulvin tablet were preliminarily determined in 18 liters of pH 7.2 phosphate buffer and in 900 ml of 40% dimethylformamide as test media. Addition of dimethylformamide affected the dissolution behavior of the formulations. The products, three microsize and one ultramicrosize, were selected for further studies on the bioavailability in humans and dissolution. Significant differences among the formulations were found in serum levels Cmax, and AUC47.5 hr, but not in AUC infinity and tmax. The maximum difference of Cmax was approximately 40%. The ultramicrosize product showed lower Cmax and serum levels at earlier sampling times than two microsize products. The dissolution rates determined under sink and nonsink conditions without pretreatment significantly correlated with the serum level at 1 hr but not with the other in vivo parameters. Only the dissolution rate determined by the sink method with pretreatment with a small quantity of water (1.0 ml) and plastic beads significantly correlated with serum levels at 3 and 5 hr, Cmax, and AUC 47.5 hr.

Effect of food on the bioavailability of griseofulvin from microsize and PEG ultramicrosize (GRIS-PEG) plain tablets

Effect of food on the bioavailability of griseofulvin from its two plain tablets, a commercial microsize product and a PEG ultramicrosize (GRIS-PEGR) one, was investigated. The drug was dissolved at a slower rate from ultramicrosize formulation than from microsize one in 18 1 of pH 7.2 buffer but at a little faster rate in 40% dimethylformamide. When administered to fasting subjects, the microsize product showed higher serum levels and peak serum level than ultramicrosize one but the extent of the bioavailability was nearly the same. A standard breakfast enhanced the rate of absorption of the drug from both the products, especially from ultramicrosize one, and those products were equivalent in the rate and extent of bioavailability after food ingestion. The peak serum level of ultramicrosize product in nonfasting was about twice higher than that in fasting subjects. The different intensities of food effect on the bioavailabilities from two dosage forms suggest that formulation factors should be considered for the evaluation of food effect.

Percutaneous absorption of griseofulvin and proquazone in the rat and in isolated human skin

Ointments containing griseofulvin and proquazone, respectively, were made up of monoglycerides of medium chain length and an aprotic solvent, glycerinformal. The ointments were applied topically on the back of bile cannulated rats. The total amount absorbed percutaneously and the permeability constants of both drugs were considerably higher for the ointments than for simple solutions of the drugs without monoglycerides. Distribution of the labeled drugs in rat skin has been demonstrated by microautoradiography. Concentrations of the drugs in the different layers of human skin together with the medium flow rates have been determined 16 h after administration of the ointments onto isolated human skin. Monoglycerides of medium chain length enhance significantly the permeability of the stratum corneum for solutes.

Influence of high fat diet on GI absorption of griseofulvin tablets in man

A controlled crossover study was carried out on five volunteers to substantiate reported effects of fat intake on the bioavailability of griseofulvin. The urinary excretion of 6-demethylgriseofulvin was monitored for 24 h following the administration of 125-mg griseofulvin tablets in the fasting state and after a fatty diet. Statistical analysis of excretion data indicated a significant increase in both rate and extent of absorption of griseofulvin as a result of fat intake. Excretion rate profiles obtained permitted insight into mechanisms possibly involved in the observed drug-diet interaction.

Bioavailability of microsize and ultramicrosize griseofulvin products in man

The relative bioavailability of ten marketed dosage forms of griseofulvin was evaluated in two separate crossover studies. Each study utilized 12 healthy subjects, with eight of the subjects being common to both studies. Plasma griseofulvin concentrations were determined 1, 2, 3, 4, 6, 8, 10, 25, 34, 49, and 73 hr after dosing, using a high-pressure liquid chromatographic method. The "high-dose" study compared four microsize dosage forms administered as 500-mg doses and two ultramicrosize formulations given as 250-mg doses. The "low-dose" study employed four 250-mg microsize products and two 125-mg ultramicrosize products. The individual plasma level-time profiles for the majority of doses suggested prolonged absorption of microsize griseofulvin. The ultramicrosize dosage forms exhibited peak concentrations which were not significantly different (p > 0.05) from those of the microsize products administered as twice the dose. In the high-dose study, the two 250-mg ultramicrosize dosage forms exhibited areas under the plasma level-time curve (AUC) which were significantly (p < 0.05) less than the AUCs for all but one of the 500-mg microsize products. In the low-dose study the AUCs for the ultramicrosize products were significantly lower than the AUCs for all of the microsize dosage forms. Significant differences were also noted among the AUCs for the microsize products, although the maximum difference was less than 20% in both studies. A comparison of the AUCs observed in the high- and low-dosage studies revealed that the AUCs for two of the 500-mg microsize dosage forms were only approximately 75% the AUC predicted from the 250-mg dose for the eight subjects common to both studies. All other formulations exhibited a dose proportionality for AUC.

Bioavailability of different brands of griseofulvin tablets and its correlation to dissolution data

A bioavailability study was carried out in man on five brands of griseofulvin tablets. Urinary excretion of free and total 6-demethylgriseofulvin was monitored for 24 h after single 125 mg doses. The bioavailability information, deduced from metabolite excretion data, pointed to inter-brand differences in rate but not extent of griseofulvin absorption. Correlations were sought between in vivo data and previousely determined dissolution parameters using a two phase system. Based on the correlation coefficients obtained, dissolution data proved predictive of absorption rates of griseofulvin tablets. Meaningful correlation between dissolution rate and extent of griseofulvin absorption was not observed.