Metabolism of norethisterone in the greyhound

RATIONALE

Norethisterone has been used as a successful oral contraceptive in humans for many years. It was recently permitted for use as an oestrus suppressant in racing greyhounds. To monitor the use of norethisterone as part of a routine drug surveillance programme, knowledge of its metabolism was required to enable detection.

METHODS

Gas chromatography/mass spectrometry and selective derivatisation techniques have been used to identify urinary metabolites of norethisterone following oral administration to the greyhound. Metabolites were extracted using solid-phase and liquid-liquid extraction techniques.

RESULTS

Several metabolites were identified, including reduced, mono-, di- and trihydroxylated steroids. The major metabolites observed were 17α-ethynyl-5β-estrane-3α,17β-diol, 17α-ethynyl-5α-estrane-3β,17β-diol, three 17α-ethynylestranetriol stereoisomers and two 17α-ethynylestranetetrol stereoisomers. The major metabolites were predominantly excreted as glucuronic acid conjugates and detection of the administration of norethisterone was possible for up to 8 days post-dose using the methods described. The nandrolone metabolites, 19-norepiandrosterone, estranediol and 19-noretiocholanolone, were also identified in the post-administration samples collected up to 8 h after dosing the treated animals.

CONCLUSIONS

The urinary metabolites identified in this study have further increased the knowledge of steroid metabolism in the greyhound, providing information to support routine drug testing programmes for greyhound racing.

Ozone oxidation of pharmaceuticals, endocrine disruptors and pesticides during drinking water treatment

This study investigates the oxidation of pharmaceuticals, endocrine disrupting compounds and pesticides during ozonation applied in drinking water treatment. In the first step, second-order rate constants for the reactions of selected compounds with molecular ozone (k(O3)) were determined in bench-scale experiments at pH 8.10: caffeine (650+/-22M(-1)s(-1)), progesterone (601+/-9M(-1)s(-1)), medroxyprogesterone (558+/-9M(-1)s(-1)), norethindrone (2215+/-76M(-1)s(-1)) and levonorgestrel (1427+/-62M(-1)s(-1)). Compared to phenolic estrogens (estrone, 17beta-estradiol, estriol and 17alpha-ethinylestradiol), the selected progestogen endocrine disruptors reacted far slower with ozone. In the second part of the study, bench-scale experiments were conducted with surface waters spiked with 16 target compounds to assess their oxidative removal using ozone and determine if bench-scale results would accurately predict full-scale removal data. Overall, the data provided evidence that ozone is effective for removing trace organic contaminants from water with ozone doses typically applied in drinking water treatment. Ozonation removed over 80% of caffeine, pharmaceuticals and endocrine disruptors within the CT value of about 2 mg min L(-1). As expected, pesticides were found to be the most recalcitrant compounds to oxidize. Caffeine can be used as an indicator compound to gauge the efficacy of ozone treatment.

Doping in sport--2. Quantification of the impurity 19-norandrostenedione in pharmaceutical preparations of norethisterone

The finding of measurable amounts of 19-norandrostenedione in norethisterone tablets prompted us to develop an assay to quantify this steroid. 19-Norandrostenedione is an anabolic steroid whose use in sport is prohibited by the World Anti-Doping Agency (WADA). The assay was developed using isotope dilution and liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the quantification of 19-norandrostenedione in norethisterone formulations, with [3,4-(13)C(2)]-19-norandrostenedione as the internal standard. The results showed amounts up to 1.01+/-0.01microg (mean+/-S.E.M.) per tablet in those containing 5mg of norethisterone or norethisterone acetate (0.02%, w/w) and up to 0.5+/-0.01microg (mean+/-S.E.M.) per tablet (0.05%, w/w) in oral contraceptive tablets containing 0.35-1.5mg of norethisterone or norethisterone acetate. No tablet tested exceeded the British Pharmacopoeia limit of 0.1% for this impurity.

Identification of the human cytochrome P450 enzymes involved in the in vitro biotransformation of lynestrenol and norethindrone

This study examined the cytochrome P450 (CYP) enzyme selectivity of in vitro bioactivation of lynestrenol to norethindrone and the further metabolism of norethindrone. Screening with well-established chemical inhibitors showed that the formation of norethindrone was potently inhibited by CYP3A4 inhibitor ketoconazole (IC(50)=0.02 microM) and with CYP2C9 inhibitor sulphaphenazole (IC(50)=2.13 microM); the further biotransformation of norethindrone was strongly inhibited by ketoconazole (IC(50)=0.09 microM). Fluconazole modestly inhibited both lynestrenol bioactivation and norethindrone biotransformation. Lynestrenol bioactivation was mainly catalysed by recombinant human CYP2C9, CYP2C19 and CYP3A4; rCYP3A4 was responsible for the hydroxylation of norethindrone. A significant correlation was observed between norethindrone formation and tolbutamide hydroxylation, a CYP2C9-selective activity (r=0.63; p=0.01). Norethindrone hydroxylation correlated significantly with model reactions of CYP2C19 and CYP3A4. The greatest immunoinhibition of lynestrenol bioactivation was seen in incubations with CYP2C-Ab. The CYP3A4-Ab reduced norethindrone hydroxylation by 96%. Both lynestrenol and norethindrone were weak inhibitors of CYP2C9 (IC(50) of 32 microM and 46 microM for tolbutamide hydroxylation, respectively). In conclusion, CYP2C9, CYP2C19 and CYP3A4 are the primary cytochromes in the bioactivation of lynestrenol in vitro, while CYP3A4 catalyses the further metabolism of norethindrone.

Structure-activity relationships of synthetic progestins in a yeast-based in vitro androgen bioassay

The recent identification of tetrahydrogestrinone (THG), a non-marketed designer androgen used for sports doping but previously undetectable by established mass spectrometry-based urine drug screens, and its production by a facile chemical modification of gestrinone has raised concerns about the risks of developing designer androgens from numerous marketed progestins. We therefore have used yeast-based in vitro androgen and progesterone bioassays to conduct a structure-activity study assessing the intrinsic androgenic potential of commercially available progestins and their derivatives, to identify those compounds or structures with the highest risk of forming a basis for such misapplication. Progestins had a wide range of androgenic bioactivity that was not reliably predicted for individual steroids by their progestin bioactivity. 17alpha-Hydroxyprogesterone and 19-norprogesterone derivatives with their bulky 17beta-substituents were strong progestins but generally weak androgens. 17alpha-Ethynylated derivatives of testosterone, 19-nortestosterone and 18-methyl-19-nortestosterone such as gestrinone, ethisterone, norethisterone and norgestrel had the most significant intrinsic androgenicity of all the commercially marketed progestins. Facile chemical modification of the 17alpha-ethynyl group of each of these progestins produces 17alpha-methyl, ethyl and allyl derivatives, including THG and norbolethone, which further enhanced androgenic bioactivity. Thus by using the rapid and sensitive yeast bioassay we have screened a comprehensive set of progestins and associated structures and identified the ethynylated testosterone, 19-nortestosterone and 18-methyl-19-nortestosterone derivatives as possessing the highest risk for abuse and potential for conversion to still more potent androgens. By contrast, modern progestins such as progesterone, 17alpha-hydroxyprogesterone and 19-norprogesterone derivatives had minimal androgenic bioactivity and pose low risk.

Tibolone and its delta-4, 7alpha-methyl norethisterone metabolite are reversible inhibitors of human aromatase

Tibolone is used for the treatment of climacteric symptoms and osteoporosis in menopausal women. After ingestion, it is rapidly converted to a number of metabolites including 3alpha- and 3beta-hydroxy derivatives and the delta-4, 7alpha-methylnorethisterone (7alpha-MeNET) metabolite, which is rapidly cleared from circulation. Tibolone and some of its metabolites act in a tissue-selective manner to inhibit steroid sulphatase (STS) and 17beta-hydroxysteroid dehydrogenase Type 1 (17beta-HSD1) activities but also stimulate steroid sulphotransferase and 17beta-HSD2 activities. In the present study we have examined whether the ability of tibolone and its 7alpha-MeNET metabolites to regulate the activities of enzymes involved in oestrogen formation or inactivation extends to another key enzyme involved in oestrogen synthesis, the aromatase, which converts androstenedione to oestrone. Using JEG-3 choriocarcinoma cells, which have a high level of aromatase activity, tibolone and 7alpha-MeNET, but not the 3alpha- or 3beta-hydroxy metabolites, were found to inhibit aromatase activity in intact cells and also lysates prepared from these cells (up to 61% inhibition at 10muM). An investigation into the nature of aromatase inhibition by these compounds revealed that they inhibit aromatase activity by a reversible mechanism. Tibolone and 7alpha-MeNET also inhibited aromatase activity in MCF-7 breast cancer cells, which have a much lower level of aromatase activity than JEG-3 cells. It is concluded that, in addition to inhibiting STS and 17beta-HSD1, tibolone and 7alpha-MeNET may exert some of their tissue-selective effects in regulating oestrogen synthesis by also inhibiting aromatase activity.

Voltammetry and quantification of the contraceptive drug norethisterone in bulk form and pharmaceutical formulation

The electrochemical behavior of norethisterone at the mercury electrode was studied in the universal buffer of various pH values using dc-polarography, cyclic voltammetry and controlled-potential electrolysis. Norethisterone was reduced at the mercury electrode via the consumption of two electrons corresponding to reduction of the 3-keto-delta-4-group in the A-ring of the molecule. The pK(a) value (8.7) of norethisterone was determined from the polarographic and spectrophotometric measurements. A fully validated, simple, sensitive, precise and inexpensive square-wave adsorptive cathodic stripping (SWAdCS) voltammetry procedure was described for trace quantification of bulk norethisterone. The stripping voltammetry peak current of norethisterone in a universal buffer of pH 5 following its accumulation onto the hanging mercury drop electrode (HMDE) at -0.6 V (versus Ag/AgCl/KCl(s)) for 130 s showed a linear response with the concentration over the range 5 x 10(-9) to 3 x 10(-7)M norethisterone. Detection and quantitation limits of 1.5 x 10(-9) and 5 x 10(-9)M bulk norethisterone, respectively, were achieved. The proposed procedure was successfully applied for the assay of norethisterone in Steronate tablets without interference from excipients.

Effects of intranasal versus oral hormone therapy on asymmetric dimethylarginine in healthy postmenopausal women: a randomized study

OBJECTIVE

Oral estrogens reduce asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase, and an independent risk factor for cardiovascular disease. This study was conducted to compare the effect on ADMA between intranasal and oral 17beta-estradiol (E2) combined with norethisterone (acetate) (NET(A)) administration in postmenopausal women.

METHODS

In a two-center, randomized, double-blind, comparative study 90 healthy postmenopausal women (age 56.6+/-4.7 years) received daily continuous combined intranasal E2/NET 175 microg/275 microg (n=47) or oral E2/NETA 1 mg/0.5 mg (n=43) for one year. At baseline, week 12 and 52, plasma concentrations of ADMA, arginine and symmetric dimethylarginine (SDMA) were measured by high-performance liquid chromatography.

RESULTS

Oral E2/NETA reduced ADMA concentrations (-7.4%; 95% confidence interval (CI) -10.4 to -4.4%), while intranasal E2/NET had no effect (-0.8%; 95% CI -3.7 to 2.1%) after 52 weeks. In both groups, arginine was transiently decreased compared to baseline at week 12 (intranasal: -6.1%; 95% CI -9.1 to -3.0%; oral: -6.5%; 95% CI -10.9 to -2.1%). Only oral E2/NETA reduced SDMA concentrations.

CONCLUSIONS

Oral administration of E2/NETA reduced ADMA and SDMA concentrations, whereas intranasal administration did not. Both treatments transiently reduced arginine. The decrease in ADMA by oral estrogens could be a key phenomenon in the modulation of nitric oxide synthesis by postmenopausal hormone therapy.

Biphasic versus monophasic oral contraceptives for contraception

BACKGROUND

Side effects caused by oral contraceptives discourage compliance with, and continuation of, oral contraceptives. Three approaches have been used to decrease these adverse effects: reduction of steroid dose, development of new steroids, and new formulas and schedules of administration. The third strategy led to the biphasic oral contraceptive pill.

OBJECTIVES

To compare biphasic with monophasic oral contraceptives in terms of efficacy, cycle control, and discontinuation due to side effects. Our a priori hypotheses were: (a) biphasic oral contraceptives are less effective than monophasic oral contraceptives in preventing pregnancy; (b) biphasic oral contraceptives cause more side effects, give poorer cycle control, and have lower continuation rates.

SEARCH STRATEGY

We searched the computerized databases MEDLINE, EMBASE, POPLINE, LILACS and CENTRAL. In addition, we searched the reference lists of all potentially relevant articles and book chapters. We also contacted the authors of relevant studies and pharmaceutical companies in Europe and the USA.

SELECTION CRITERIA

We included randomized controlled trials comparing any biphasic with any monophasic oral contraceptive when used to prevent pregnancy.

DATA COLLECTION AND ANALYSIS

We examined the studies found during the various literature searches for possible inclusion and assessed their methodology using Cochrane guidelines. We contacted the authors of all included studies and possibly randomized studies for supplemental information about methodology and outcome. We entered the data into RevMan, and calculated Peto odds ratios for the incidence of intermenstrual bleeding, absence of withdrawal bleeding, and study discontinuation due to intermenstrual bleeding.

MAIN RESULTS

Only one trial of limited quality compared a biphasic and monophasic preparation. Percival-Smith 1990 examined 533 user cycles of a biphasic pill (500 microg norethindrone/35 microg ethinyl estradiol for 10 days, followed by 1000 microg norethindrone/35 microg ethinyl estradiol for 11 days; Ortho 10/11) and 481 user cycles of a monophasic contraceptive pill (1500 microg norethindrone acetate/30 microg ethinyl estradiol daily; Loestrin). The study found no significant differences in intermenstrual bleeding, amenorrhea and study discontinuation due to intermenstrual bleeding between the biphasic and monophasic oral contraceptive pills.

AUTHORS' CONCLUSIONS

Conclusions are limited by the identification of only one trial, the methodological shortcomings of that trial, and the absence of data on accidental pregnancies. However, the trial found no important differences in bleeding patterns between the biphasic and monophasic preparations studied. Since no clear rationale exists for biphasic pills and since extensive evidence is available for monophasic pills, the latter are preferred.

Lack of aromatisation of the 3-keto-4-ene metabolite of tibolone to an estrogenic derivative

Tibolone is used for the treatment of climacteric symptoms in postmenopausal women. It is metabolised in a tissue-specific manner so that while some metabolites exert estrogenic effects on bone and the CNS, others are thought to protect the breast and endometrium from estrogenic stimulation. Tibolone is a 7alpha-methyl derivative of 19-norethynodrel. Since the introduction of synthetic progestagens for therapeutic use there has been considerable controversy as to whether they can undergo aromatisation to give rise to the potent estrogen, ethinylestradiol. In this study, we examined whether the delta-4-ene (7alpha-methyl norethisterone) metabolite of tibolone, which has a similar delta-4-ene A-ring structure to that of the estrone precursor, androstenedione, could undergo aromatisation to the potent estrogen, 7alpha-methyl ethinylestradiol. For these studies, JEG-3 choriocarcinoma cells were employed as they have a very high level of aromatase activity. TLC and HPLC procedures were developed to separate phenolic from non-phenolic compounds and were initially used to confirm that JEG-3 cells readily aromatised androstenedione to estrogens (up to 74%). The aromatisation of androstenedione to estrogens by these cells could be completely blocked with the potent aromatase inhibitor letrozole. When [(3)H] 7alpha-methyl norethisterone was incubated with JEG-3 cells no evidence for its conversion to [(3)H] 7alpha-ethinylestradiol was obtained. Radioactivity detected on the TLC plate or HPLC fractions where standard 7alpha-methyl ethinylestradiol was located, revealed that similar levels were present when 7alpha-methyl norethisterone was incubated with culture medium alone or with JEG-3 cells in the absence or presence of letrozole. From these investigations, it is concluded that 7alpha-methyl norethisterone does not undergo aromatisation to an estrogenic derivative.

[Study of drug displacement interactions by capillary electrophoresis-frontal analysis]

The interaction between 18-methyl norethindrone and ketoprofen including the displacement of ketoprofen from human serum albumin binding sites was investigated by capillary electrophoresis-frontal analysis method (CE-FA) at room temperature. A very large sample plug was introduced hydrostatically into the capillary (65 cm x 50 microm i.d., effective length of 35 cm) over 80 s at a height difference of 11 cm. The working conditions for CE-FA separation are as follows: operating voltage, 10 kV; running buffer, 67 mmol/L phosphate, pH 7.4. The unbound ketoprofen concentration was directly measured from the height of the frontal peak. When the concentration of 18-methyl norethindrone was increased from 0 to 200 micromol/L, the unbound ketoprofen concentration was found to increase from 22.4 to 26.4 micromol/L at 100 micromol/L total ketoprofen concentration and from 82.1 to 106.2 micromol/L at 200 micromol/L total ketoprofen concentration. From these data, it may be deduced that the administration of high concentration of 18-methyl norethindrone could displace ketoprofen from its secondary binding site.

Determination of the physical state of norethindrone acetate containing transdermal drug delivery systems by isothermal microcalorimetry, X-ray diffraction, and optical microscopy

Transdermal drug delivery systems (TDDS) enable a controlled drug delivery to the skin. The low permeability of the stratum corneum necessitates a high drug concentration of the polymeric matrix and often requires supersaturation. This, however, promotes crystallisation of supersaturated systems. Isothermal microcalorimetry at 25 degrees C, polarisation light microscopy, and X-ray powder diffraction (XRPD) were used to characterise the crystal growth of norethindrone acetate (NEA). The solubility of NEA in the patches determined by these methods is about 4%. The crystallisation process could be measured reliably and with a high accuracy by microcalorimetry and microscopy. XRPD was considerably less sensitive but was the only method allowing a semi-quantitative determination of the amounts of crystals formed. The drug-associated heat measured by microcalorimetry increased proportionally with increasing NEA concentration in the concentration range of 4-10% demonstrating a constant crystallisation rate. At a higher supersaturation, such as 12% drug content, the crystallisation process was accelerated. The application of Johnson-Mehl-Avrami kinetics for the analysis of nucleation and crystal growth of the punched patches indicated a site-saturated nucleation mechanism and a one-dimensional crystal growth. The crystallisation enthalpy of NEA was -22.8+/-2.6 kJ/mol. The most specific method to observe the crystal formation is polarisation light microscopy. However, the microscopic analysis requires much longer storage times than microcalorimetry to detect crystallisation.

Not all progestins are the same: implications for usage

Recent clinical evidence showing unexpected side-effects of progestins used in contraception and hormone replacement therapy has highlighted the importance of choice of synthetic progestin. The molecular mechanisms of action of the relatively nonspecific and most widely used synthetic progestins, medroxyprogesterone acetate and norethisterone, are discussed in the context of this recent clinical evidence. Future directions involving a more mechanism-based approach for improved therapeutics, with greater specificity and fewer side-effects, are discussed.

Progesterone Receptor Ligand Binding Pocket Flexibility: Crystal Structures of the Norethindrone and Mometasone Furoate Complexes

Although progesterone, the natural ligand of the progesterone receptor (PR), has a hydrogen atom at the 17alpha position, other potent steroid agonists such as norethindrone and mometasone furoate have larger substituents at this position that are accommodated by the PR ligand binding pocket. Crystallographic analysis of PR ligand binding domain complexes clearly demonstrated that these moieties were accommodated by local shifts of the protein main chain and by adoption of alternative side chain rotamer conformations of ligand-proximal amino acids. These conformational changes imparted a ligand-specific volume to the binding pocket, from 490 A3 in the metribolone complex to 520 A3 in the norethindrone complex, 565 A3 in the progesterone complex, and 730 A3 in the mometasone furoate complex. Despite these marked alterations in binding pocket volume, critical interactions essential for establishment of an active AF2 conformation were maintained.

Use of isothermal heat conduction microcalorimetry, X-ray diffraction, and optical microscopy for characterisation of crystals grown in steroid combination-containing transdermal drug delivery systems

The combined application of the steroids estradiol (E2) hemihydrate and norethindrone acetate (NEA) is desirable for hormone replacement therapy. Transdermal drug delivery systems (TDDS) enable a controlled delivery of these drugs to the skin. However, in order to attain high skin permeation rates the concentration of the dissolved drugs in the TDDSs has to be high. This often results in supersaturated systems with a high crystallisation tendency. The combination of NEA and E2-hemihydrate in the acrylic matrix of patches yields crystals that are different from single drug systems. A new crystal phase showing additional X-ray powder diffraction peaks and a new feather-like crystal shape appeared. The crystal formation was considerably accelerated and enhanced by increasing E2 contents in the patches. The new crystal phase seems to be kinetically favoured compared with crystals appearing from pure E2-hemihydrate or NEA. A crystallisation enthalpy of -7.9+/-0.95 kJ/mol in the matrix containing a 1:3 mixture of E2-hemihydrate and NEA was determined by isothermal microcalorimetry. The crystallisation rate increased with higher drug concentrations. In addition, the influence of patch pre-treatment at 80 degrees C prior to storage on crystallisation was investigated. This treatment enabled a slight reduction of the crystallisation in the TDDSs. Microcalorimetry enabled the classification of various additives according to their influence on the crystallisation process.

Chemical and analytical characterization of related organic impurities in drugs

A system is proposed for the classification of related organic impurities in drugs and drug products including among others (separated and non-separated) intermediates, various kinds of by-products, among them products of different side reactions, epimeric/diastereomeric, enantiomeric impurities, impurities in natural products, and finally degradation products. Examples are taken mainly from the author's own experience and from among the named impurities in the European Pharmacopoeia with focus on impurities in hydrocortisone, prednisolone, enalapril maleate, lisinopril, ethynodiol diacetate, pipecuronium bromide, cimetidine, and ethynylsteroids. The methodological aspects of impurity profiling from the detection to the identification/structure elucidation and quantitative determination of impurities are briefly summarized.

All progestins are not created equal

A variety of progestins are available for therapeutic use. It is convenient to classify them into those related in chemical structure to progesterone or testosterone. Progestins related to progesterone can be subdivided into pregnanes and 19-norpregnanes, whereas those related to testosterone can be subdivided into those with and without a 17-ethinyl group. 17-Ethinylated progestins consist of the families of norethindrone (estranes) and levonorgestrel (13-ethylgonanes). Progestins administered orally undergo extensive hepatic first pass metabolism primarily by reduction and conjugation, and in most instances, relatively high progestin doses are required for therapeutic use. There are limited reliable data on the pharmacokinetics of most progestins. Some progestins are prodrugs, requiring transformation prior to exhibiting progestational activity. Qualitative and quantitative tests utilizing either human or animal species have been used to establish progestin potency. However, profound differences in progestational activity are often observed between human and animal tissues. Also, there is a misconception about androgenicity of progestins due largely to extrapolation of data from rat studies to the human. Progestins differ widely in their chemical structures, structure-function relationships, metabolism, pharmacokinetics, and potencies; they are not created equal.

Ab initio electronic structure of the progestogen norethisterone and its 5 alpha-derivatives

The steroid 17 alpha-ethynyl-19-nor-4-androsten-17 beta-ol, 3-one (Norethisterone; NET) and its 5 alpha-dihydro (5 alpha-NET), 3 alpha- and 3 beta-tetrahydro derivatives (3 alpha,5 alpha- and 3 beta,5 alpha-NET), were comparatively studied by the ab initio quantum mechanics theory. Additionally, 5 alpha-androstan-3 beta,17 beta-diol (ADIOL) was also studied. The Hartree-Fock method and the 6-31G(*) basis set were used to obtain the lowest energy conformation, geometries, electronic structure and physicochemical properties of the steroids. The results showed bond distances and valence angles similar among all steroids, but some differences in dihedral angles in the A-B-ring system were observed. The electronic structure analysis showed that NET has both frontier orbitals that is, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) located at the C4-C5 pi-bond. In A-ring reduced derivatives, the HOMO was found at the 17 beta-OH and ethynyl groups. In the case of 5 alpha-NET, the LUMO was confined to the A-ring and its C3 carbonyl group while the two NET tetrahydro-reduced derivatives showed the LUMO at the 17 beta-OH and ethynyl groups. The energy changes of the rotational barrier of the 17 beta-OH group suggest that its movement is somewhat restricted by the 17 alpha-ethynyl group. Interestingly both groups at C17 form a single electrostatic potential with high electronic density. On the other side, the 19-nor condition increases the A-ring mobility. However, the 3 beta-OH group of 3 beta,5 alpha-NET may rotate without significant energy differences as compared to the same group in ADIOL. The electronic structure of NET and its A-ring reduced derivatives explains in some extent their interaction with androgen and progesterone receptors as well as their selectivity for the estrogen alpha-receptor.

Norethindrone acetate (NA) and ethinyl estradiol (EE) related oxidative transformation products in stability samples of formulated drug product: synthesis of authentic references

Preparative chemical methods for the synthesis of eight oxidative transformation products of ethinyl estradiol (EE) and norethindrone acetate (NA) are described. The prepared materials are useful as reference materials and standards for pharmaceutical analysis of EE and NA as bulk chemical or in formulated product. All eight products result from oxidation of the A and/or B rings of the parent compounds. Oxidation of the heteroannular 3,5 dienyl acetate derivative of NA resulted in the 6 alpha-hydroxy, 6 beta-hydroxy and 6-keto NA. Oxidation of 6-keto NA led to the preparation of 6 alpha-hydroxy, 6 beta-hydroxy, 6-keto- and Delta(6) EE. Delta(11) EE was prepared from estrone.

Influence of the substitution of 11-methylene, delta(15), and/or 18-methyl groups in norethisterone on receptor binding, transactivation assays and biological activities in animals

The profile of norethisterone and newly developed derivatives thereof were assessed by in vitro binding and transactivation assays on progesterone (PR) as well as on androgen (AR) receptors and by subcutaneous treatment in in vivo models. The following in vivo models were performed: A McPhail test for progestational activity in immature rabbits, an ovulation inhibition test in cycling rats and a Hershberger test for androgenic activity in immature orchidectomised rats. The compounds tested were: norethisterone (NET), 11-methylene-NET (11-NET), Delta(15)-NET (15-NET), 18-methyl-NET (18-NET, Levonorgestrel, LNG), 11-methylene-Delta(15)-NET (11, 15-NET), 11-methylene-18-methyl-NET (11,18-NET, 3-keto-desogestrel, Etonogestrel, ETG), (Delta(15)-18-methyl-NET (15,18-NET, Gestodene, GSD) and 11-methylene-Delta(15)-18-methyl-NET (11,15,18-NET). Compared to the non-substituted compound NET, the binding to and agonistic activity via PR was increased for all the three mono-substituted compounds, although the stimulatory effect of 15-NET was only twofold. Compounds with 18-methyl in combination with Delta(15) (GSD), with 11-methylene (ETG) or with both combined showed clear synergistic effects, leading to equipotent compounds. If the 18-methyl group was lacking as in 11,15-NET, potency was lower than for ETG or GSD, but higher than for 18-NET (LNG). A correlation coefficient of 0.9 was found between binding affinity and agonistic potency. With respect to the AR binding and transactivation activities, the 18-methyl group potentiated androgenic in vitro activity (LNG). The 11-methylene group increased relative binding affinity in NET, but reduced androgenic activity clearly when also other substituents were present (11,15-NET, ETG and 11,15,18-NET). The Delta(15) bond alone did not change the binding in NET, but decreased androgen binding, induced by the 18-methyl substituent, in GSD and 11,15,18-NET. Transactivation activity was also diminished in the compounds having a Delta(15) bond. In the McPhail test mono-substitution of NET increased the progestagenic in vivo activity three to five times. Bi- and tri-substitution enhanced the activity further. With respect to ovulation inhibition mono-substitution of NET resulted in three to nine times more potent compounds, whereas bi- and tri-substitution increased potency further, except for 11,15-NET, which was as active as 11-NET. The relative progestagenic potencies in the McPhail and ovulation inhibition tests, correlated significantly with those of the relative binding affinity values (correlation coefficient of 0. 91 and 0.93, respectively) and relative transactivation activity values (0.88 and 0.81) for the PR. In the Hershberger test, all the compounds increased androgenic activity with respect to growth of ventral prostate weight compared to NET, with the exception of 11, 15-NET and 11,15,18-NET. The androgenic activity was negligible for these latter compounds. The androgenicity of both 18-NET (LNG) and 15,18-NET (GSD), on the other hand, was significantly higher than that of 11,18-NET (ETG). The results of this in vivo test are in line with the AR binding and transactivation activity values (correlation coefficients of 0.86 and 0.88). In addition, selectivity indices were calculated by dividing the progestational potencies by androgenic potencies for both in vitro and in vivo assays. ETG and GSD had clearly higher in vitro and in vivo indices than the other compounds with NET and LNG having the lowest indices. Because the androgenicity of 11,15-NET and 11,15,18-NET was very low, no exact selectivity ratios could be calculated for these compounds. From these experiments we may conclude that small structural modifications exert enhancement of progestational activity and a clear reduction in androgenicity leading to very selective progestagenic compounds. The influence of bi-substitution is additive over mono-substitution, whereas tri-substition is not additive. (ABSTRACT TRUNCATED)

O-(fluoresceinylmethyl)hydroxylamine (OFMHA): a reagent for the preparation of fluorescent O-(fluoresceinylmethyl)oxime (FMO)-steroid conjugates

The 5 and 6-isomers of O-(fluoresceinylmethyl)hydroxylamine reacted with a representative sample of oxo-steroids (6-oxoestradiol, estrone, norethindrone, cortisol, progesterone, and digitoxin-dialdehyde) to produce O-(fluoresceinylmethyl)oxime conjugates in a single step in 24-84% yield after preparative high performance liquid chromotography.

Induction of micronuclei and of enzyme-altered foci in the liver of female rats exposed to progesterone and three synthetic progestins

Progesterone (PG) and three structurally similar synthetic progestins-norethisterone (NE), allylestrenol (AE), and dydrogesterone (DG)-have been compared for their ability to induce the formation of micronuclei and of enzyme-altered foci in the liver of female rats. In the micronucleus assay, carried out in rats given a single p.o. dose of 100 mg kg-1 3 days before partial hepatectomy and sacrificed for cell sampling 2 days later, the frequency of micronucleated hepatocytes was 3.5-fold higher than in controls with PG, 2.8-fold with DG, 2.2-fold with NE and 2.1-fold with AE, but the increase was statistically significant only for PG. In the liver foci assay, performed to evaluate the tumor initiating activity of p. o. dosing with 100 mg kg-1 once a week for 6 successive weeks, the values of the number and area of gamma-glutamyltranspeptidase-positive foci were, as compared to controls, 15.9- and 100-fold higher with NE, and 13.9- and 52-fold higher with AE, but only the increase of area produced by NE was statistically significant; PG and DG did not display in this test any activities. Considered together with previous findings, these results suggest that NE might be biotransformed in the liver into reactive species and thus behave as a weak genotoxic agent.

Quantitative determination of norethisterone acetate in human plasma by capillary gas chromatography with mass-selective detection

An analytical method for the determination of norethisterone acetate (NETA) in human plasma by capillary gas chromatography-mass-selective detection (GC-MS), with testosterone acetate as internal standard, was developed and validated. After addition of the internal standard, the compounds were extracted from plasma at basic pH into diethyl ether-dichloromethane (3:2, v/v), which was then evaporated to dryness. The compounds were converted into their pentafluoropropionyl derivatives which were determined by gas chromatography using a mass selective detector at m/z 486 for NETA and m/z 476 for the internal standard. Intra-day and inter-day accuracy and precision were found suitable over the range of concentrations between 0.10 to 10 ng/ml. The method was applied to clinical samples.

Steroids 49. Investigations on the dehydration of 17 alpha-ethynyl-17 beta-hydroxysteroids

The acidic dehydration of 17 alpha-ethynyl-17 beta-hydroxysteroids (1-3) was investigated. On reaction with thionyl chloride, phosphorus oxychloride, and formic acid, the desired dehydration was accompanied by chlorination, Wagner-Meerwein rearrangement, and D-homoaromatic rearrangement. The structure of the product from the transformation of 17 beta-hydroxypregn-20-yne derivative (3) on reaction with formic acid was misjudged. It was regarded as a pregn-16-en-20-yne (10) instead of the actually rearranged D-homoaromatic compound (11). As a consequence, physical data corresponding to this latter structure have been cited in the literature as those of pregn-16-en-20-yne derivative (10). This confusion prompted us to prepare compounds of both types (4, 9, 10, and 11), the characterization of which is here described.

Steroids 51. An improved synthesis of ORG 2058 and the synthesis of [3H]ORG 2058

16 alpha-Ethyl-21-hydroxy-19-norpregn-4-ene-3,20-dione (ORG 2058) is a ligand widely used in progesterone receptor assays. An improved synthesis of the compound is reported, starting from norethisterone acetate. The preparation of the tritiated radioligand [3H]ORG 2058 is also described.