Pharmacoinformatics study of Piperolactam A from Piper betle root as new lead for non steroidal anti fertility drug development.

Fertility control is a burning problem all over the world to regulate population overflow and maintain ecological balance. This study is an in-silico approach to explore a non-steroidal lead as contraceptive agent in order to avoid several contraindications generated by steroidal analogues. Piperolactam A, an aristolactam isolated from Piper betle Linn. showed binding affinity towards estrogen and progesterone receptor as -8.9 and -9.0Kcal/mol (inhibition constant Ki=0.294µM and 0.249µM) respectively which is even larger than that of reported antagonists such as Rohitukine and OrgC (binding affinity -8.7 and -8.4Kcal/mol; Ki 0.443µM and 0.685µM respectively). The binding site exploration displayed more hydrogen bonding of Piperolactam A (His 524, Leu 346, Thr 347) than Rohitukine and OrgC (Leu 718) with associated receptors which was further confirmed by molecular dynamics simulations. The drug-likeliness of the compound has been proved from its tally with Lipinsky's Rule of Five and lowered toxicity such as cardiac toxicity, liver toxicity, mutagenicity and ecological toxicity. Endocrine disruptome and later docking guided molecular simulations revealed that Piperolactam A has weaker binding affinity and/or lower probability of binding with nuclear receptors especially hERG and cytochrome P450. The high Caco-2 permeability suggested more bioavailability hence more therapeutic efficacy of the drug.

Early adolescent Depo-Provera exposure increases stillbirths in adult sooty mangabeys.

The 3-month injectable contraceptive medroxyprogesterone acetate (MPA; Depo-Provera) is a synthetic progestin that protects against pregnancy by suppressing ovulation. Studies have focused on the resumption of ovulation after MPA-treatment cessation but neglected potential long-term effects of MPA exposure on future successful reproduction. MPA is frequently administered to adolescent girls; however, long-term fertility effects of adolescent MPA exposure have not been explored. We investigated fertility after extended MPA exposure in a species of old world primate, the sooty mangabey (Cercocebus atys). Female sooty mangabeys (n=31) received chronic MPA-treatment for 4-8 years. At MPA-treatment onset, subjects were either parous adults (n=14) or nulliparous adolescents (n=17), with adolescent-treated subjects being further divided into those who had reached first ovulation (n=10) and those who had not (n=7). After MPA-treatment cessation, adolescent-treated females had a significantly higher incidence of stillbirth than did age-matched and parity-matched controls, whereas adult-treated females did not differ from their matched controls. Females placed on MPA-treatment prior to first ovulation had a significantly higher incidence of stillbirth post-treatment than did females placed on MPA-treatment after first ovulation. Diabetic females had an increased incidence of stillbirth as compared to nondiabetic females; however, when controlling for diabetes, MPA exposure prior to first ovulation was still a significant positive predictor of stillbirth. These findings suggest that the post-treatment fertility effects of chronic MPA exposure vary with the developmental timing of treatment onset and raise concern about the use of MPA as a contraceptive for adolescent girls.

A critical examination of the mode of action of quinacrine in the reproductive tract in a 2-year rat cancer bioassay and its implications for human clinical use.

A rat carcinogenicity bioassay (CaBio) of quinacrine was reanalyzed to investigate its mode of tumor induction. Quinacrine's effects in the rat uterus when administered as a slurry in methylcellulose were contrasted with the human clinical experience which uses a solid form of the drug, to determine the relevance of the tumors produced in the rat to safe clinical use of quinacrine for permanent contraception (QS). A review was performed of the study report, dose feasibility studies, and clinical evaluations of women who had undergone the QS procedure. The top three doses of quinacrine in the CaBio exceeded the maximum tolerated dose, and produced chronic damage, including inflammation, resulting in reproductive tract tumors. Chronic inflammation was significantly correlated with the tumors; there was no evidence of treatment-related tumors in animals without chronic inflammation or other reproductive system toxicity. Because such permanent uterine damage and chronic toxicity have not been observed in humans under therapeutic conditions, we conclude that this mode of action for tumor production will not occur at clinically relevant doses in women who choose quinacrine for permanent contraception.

The synthetic progestin levonorgestrel is a potent androgen in the three-spined stickleback (Gasterosteus aculeatus).

The use of progestins has resulted in contamination of aquatic environments and some progestins have in experimental studies been shown to impair reproduction in fish and amphibians at low ng L(-1) concentrations. The mechanisms underlying their reproductive toxicity are largely unknown. Some progestins, such as levonorgestrel (LNG), exert androgenic effects in mammals by activating the androgen receptor (AR). Male three-spined stickleback (Gasterosteus aculeatus) kidneys produce spiggin, a gluelike glycoprotein used in nest building, and its production is directly governed by androgens. Spiggin is normally absent in females but its production in female kidneys can be induced by AR agonists. Spiggin serves as the best known biomarker for androgens in fish. We exposed adult female sticklebacks to LNG at 5.5, 40, and 358 ng L(-1) for 21 days. Androgenic effects were found at LNG concentrations ≥40 ng L(-1) including induction of spiggin transcription, kidney hypertrophy, and suppressed liver vitellogenin transcription. These are the first in vivo quantitative data showing that LNG is a potent androgen in fish supporting the contention that androgenic effects of certain progestins contribute to their reproductive toxicity.

Disrupted oogenesis in the frog Xenopus tropicalis after exposure to environmental progestin concentrations.

Levonorgestrel is a synthetic progesterone commonly used in pharmaceuticals (e.g., in contraceptives). It is found in sewage treatment plant effluents at concentrations up to 30 ng/L and was recently shown to pose a threat to egg laying in fish. Information on the susceptibility of adult amphibians to progestin toxicity is lacking. The present study aimed to 1) characterize progestogenic effects on the full cycle of oogenesis (egg development) in frogs and 2) determine female amphibians' susceptibility to reproductive impacts from progestogenic compounds in the environment. Sexually mature female Xenopus tropicalis were exposed to levonorgestrel via the surrounding water for 7 days (0, 51, or 307 ng/L) or 28 days (0, 1.3, 18, 160, or 1240 ng/L). Their ovaries were analyzed histologically with respect to frequencies of immature (in early meiotic prophase I), previtellogenic, vitellogenic, mature, and atretic oocytes. The 28-day exposure caused reduced proportions of oocytes at immature, vitellogenic, and mature stages, and increased proportions of previtellogenic oocytes compared with the control. The lowest tested concentration, 1.3 ng/L, increased the proportions of previtellogenic oocytes and reduced the proportions of vitellogenic oocytes, indicating inhibited vitellogenesis. The present study shows that progestin concentrations found in the aquatic environment impaired oogenesis in adult frogs. Our results indicate that progestogenic effects on oocyte development include interrupted germ cell progression into meiosis and inhibited vitellogenesis. Considering the crucial role of oogenesis in female fertility, our results indicate that progestogenic pollutants may pose a threat to reproduction in wild amphibian populations.

The synthetic gestagen levonorgestrel impairs metamorphosis in Xenopus laevis by disruption of the thyroid system.

Synthetic gestagens, including levonorgestrel (LNG), are active compounds in contraceptives, and several studies report their occurrence in surface waters. However, information about endocrine-disrupting effects in nontarget organisms is scarce. The present study investigated effects of LNG exposure on thyroid hormone-dependent metamorphosis of Xenopus laevis. Premetamorphic X. laevis tadpoles at Nieuwkoop and Faber (NF) stage 48 were exposed in a flow-through culture system to four LNG concentrations (10(-11), 10(-10), 10(-9), and 10(-8)M) over the period of metamorphosis. At NF 58 and 66, tadpoles were examined sex specifically. Developmental time and organismal responses were recorded and correlated with molecular and histopathological endpoints. Exposure to 10(-8)M LNG caused an inhibition of metamorphosis resulting in developmental arrest at early climax stages as giant tadpoles or tailed frogs. In brain-pituitary tissue of NF 58 tadpoles, gene expression of thyroid-stimulating hormone (ß-subunit; TSHß), TH receptor ß (TRß), and deiodinase type 3 (D3) was not changed. Instead, prolactin (PRL) messenger RNA (mRNA) was significantly increased by 10(-9)M LNG in females and by 10(-8)M LNG in both sexes. In NF 66 tadpoles, mRNA levels of TSHß mRNA were significantly increased in the 10(-9) and 10(-8)M LNG treatment groups indicating a hypothyroid state. No changes of TRß, D3, and PRL gene expression were detected. Histopathological evaluation of thyroid gland sections revealed no typical sign of hypothyroidism but rather an inactivated appearance of the thyroid. In conclusion, our data demonstrate for the first time a completely new aspect of thyroid system disruption caused by synthetic gestagens in developing amphibians.

Molecular effects and bioaccumulation of levonorgestrel in the non-target organism Dreissena polymorpha.

Bioaccumulation and effects of the contraceptive hormone levonorgestrel were examined in the non-target organism Dreissena polymorpha. Molecular biomarkers of biotransformation, elimination, antioxidant defence and protein damage were analyzed after exposure to increasing concentrations of levonorgestrel in a flow-through system. The lowest concentration (0.312 µg L(-1)) was 100-fold bioconcentrated within four days. A decrease of the bioconcentration factor was observed within one week for the highest test concentrations (3.12 and 6.24 µg L(-1)) suggesting enhanced excretory processes. The immediate mRNA up-regulation of pi class glutathione S-transferase proved that phase II biotransformation processes were induced. Disturbance of fundamental cell functions was assumed since the aryl hydrocarbon receptor has been permanently down-regulated. mRNA up-regulation of P-glycoprotein, superoxide dismutase and metallothioneine suggested enhanced elimination processes and ongoing oxidative stress. mRNA up-regulation of heat shock protein 70 in mussels exposed to the two highest concentrations clearly indicated impacts on protein damage.

Design and synthesis of 3-(azol-1-yl)phenylpropanes as microbicidal spermicides for prophylactic contraception.

We designed a series of 25 3-(azol-1-yl)phenylpropanes which yielded 10 compounds (3, 4, 7, 8, 13, 14, 19, 21, 23, 26) that irreversibly immobilized 100% human sperm at 1% (w/v) concentration in 60s; 12 compounds (8, 9, 15, 16, 19-21, 23-25, 27, 28) that showed potent microbicidal activity at 12.5-50 µg/mL against Trichomonas vaginalis; and 17 compounds (3-11, 13, 15, 19, 21, 23, 26, 28, 30) that exhibited potent anticandida activity with minimum inhibitory concentration (MIC) of 12.5-50 µg/mL. Almost all the compounds exhibited high level of safety towards normal vaginal flora (Lactobacillus) and human cervical (HeLa) cells in comparison to the marketed spermicide nonoxynol-9 (N-9). All the biological activities were evaluated in vitro. Two compounds (4, 8) with good safety profile exhibited multiple (spermicidal, antitrichomonas and anticandida) activities, warranting further lead optimization for furnishing a prophylactic vaginal contraceptive.

Collaborative work on evaluation of ovarian toxicity. 1) Effects of 2- or 4-week repeated-dose administration and fertility studies with medroxyprogesterone acetate in female rats.

As a part of the collaborative study to evaluate the relationship between histopathological changes of the ovary and functional changes in female fertility, 2- and 4-week repeated-dose toxicity studies and a female fertility study were conducted using female Crl:CD(SD) rats using a synthetic progestagen of medroxyprogesterone acetate (MPA) as a test compound. MPA was administered to female rats by gavage at 0, 0.4, 2.0 and 10 mg/kg/day for 2 and 4 weeks to assess the histopathological changes of ovaries and to pregnant rats at the same doses from 2 weeks prior to mating until day 7 of gestation to examine female fertility. The number of non-pregnant female rats with irregular estrous cycle increased in number and there was a decrease in weight of ovaries was observed at doses > or = 2.0 mg/kg in the 2- and 4-week-treatment groups. The histopathological examination revealed an increased number of large atretic follicles and decreases in currently formed corpora lutea and previously-formed large or small ones were observed at the same doses in the 2- and 4-week treatment groups. In female fertility study, the number of animals with an irregular estrous cycle and elongation of mean estrous cycle increased at 0.4 mg/kg, with no changes in fertility. A decreased number of copulating animals and a decreased gestation rate with low preimplantation loss were observed in the 2.0 mg/kg-treatment group and no copulation was observed in the group treated with 10 mg/kg. Based on these results, changes in fertility induced by MPA correlated well with histopathological changes of ovaries after 2 and 4 weeks of treatment, which suggests that a 2 weeks administration period is sufficient to detect ovarian toxicity of MPA with repeated dosing

Preclinical studies of alkylureas as anti-HIV-1 contraceptive.

The HIV-1 epidemic continues to spread at a rate of over 15, 000 new cases daily. HIV-1 transmission through heterosexual contact became the dominant risk for women globally. About half of the over 40 million HIV-1 infected individuals worldwide are now women. The lack of empowerment of women is the fundamental cause for the rampant spread of HIV-1 in women. Topical microbicides applied intravaginally offer an option for female-initiated HIV-1 prevention. There is an urgent need to develop microbicides with and without contraceptive qualities to also address socio-cultural settings where the woman's status is linked to fertility. A safe and efficacious anti-HIV-1 vaginal formulation is not yet available though a large number of candidates are in preclinical or clinical studies. Presently marketed topical microbicides are by and large toxic and damage the vaginal mucosa with frequent use. The microbicidal system of alkylureas evaluated here lends itself to contraceptive and non-contraceptive anti- HIV-1 formulations. Alkylureas are agents that irreversibly disrupt free and intracellular HIV-1, have a wide margin of safety and are spermicidal above their virucidal concentration without any mucosal toxicity. Butylurea, the lead compound is also effective against other sexually transmitted diseases (STDs) while sparing the normal vaginal flora. Alkylureas with longer alkyl chains still have to be explored and may have a greater selective microbicidality.

Progestogen only contraception and endometrial break through bleeding.

Progestogen only contraceptives (POC) provide a safe and effective method of fertility regulation. Unfortunately, they are commonly associated with the problem of endometrial break through bleeding (BTB), often leading to discontinuation of use. An increase in endometrial vascular fragility has been demonstrated as an important mechanism that contributes to BTB but our understanding of the interaction between exogenous steroid use and endometrial vasculature remains incomplete. This review sets out to describe a number of commonly used POC, their effects on endometrial morphology and possible molecular and cellular mechanisms that may lead to unscheduled bleeding.

Phytochemical screening and pharmacological evaluations for the antifertility effect of the methanolic root extract of Rumex steudelii.

The practice of traditional medicine for the control of fertility in most parts of Ethiopia is based on the uses of plant medicines for many years. The fact that herbal medicines have been employed for such a long time does not guarantee their efficacy and safety. The aim of the present study was, therefore, to carry out phytochemical screening, efficacy and safety studies on one of the traditionally used antifertility plants: Rumex steudelii. The secondary metabolites of the root of this plant were determined. The methanolic extract of the roots of this plant were investigated for their antifertility activity in female rats and oral LD50 was determined in mice. The identification of the secondary metabolites showed that the roots of the plant contained phytosterols and polyphenols. It was found that the extract reduced significantly (p<0.01) the number of litters. It also produced antifertility effect in a dose dependent manner and the contraceptive effect was manifested for a definite period of time. Furthermore, the extract prolonged significantly the estrus cycle (p<0.05) and the diestrous phase (p<0.01) of the rats. The wet weights of the ovaries and uterus were shown to be reduced significantly (p<0.01) and (p<0.05), respectively. The oral LD50 of the extract was found to be 5 g/kg in mice. All these observations suggest that the extract has antifertility effect and is safe at the effective antifertility doses employed in this study.

Pre-clinical safety evaluation of novel nucleoside analogue-based dual-function microbicides (WHI-05 and WHI-07).

Compounds WHI-05 [5-bromo-6-methoxy-5,6-dihydro-3'-azidothymidine-5'-(p-methoxyphenyl)-methoxyalaninyl phosphate] and WHI-07 [5-bromo-6-methoxy-5,6-dihydro-3'-azidothymidine-5'-(p-bromophenyl)-methoxyalaninyl phosphate] are aryl phosphate derivatives of zidovudine (ZDV) with anti-HIV and contraceptive activity. WHI-05 and WHI-07 differ fundamentally from currently used surfactant microbicides that are cytotoxic to genital tract epithelial cells at spermicidal concentrations. These drugs were rationally designed to bypass the thymidine kinase dependency of ZDV activation in genital tract secretions, as well as to achieve spermicidal activity. WHI-05 and WHI-07 were formulated via a non-toxic gel-microemulsion for intravaginal use as potential anti-HIV spermicides. Pre-clinical safety studies of intravaginally administered WHI-05 and WHI-07 gel-microemulsions were performed in mice and rabbits to mimic closely the intravaginal application of a microbicidal preparation in women. In addition, systemic toxicity studies were performed in mice and non-human primates. The LD10 doses for WHI-05 and WHI-07 when administered intravenously or intraperitoneally were >500 mg/kg for mice. Female cynomolgus monkeys treated with 20 mg/kg WHI-05 and WHI-07 intravenously developed no grade 2-4 systemic toxicities. Repetitive intravaginal administration of 2% WHI-05 and WHI-07 via a gel-microemulsion to achieve concentrations as high as 6.1 x 10(4) and 5.7 x 10(6) times their respective in vitro anti-HIV IC50 values, and 1200 and 5700 times their spermicidal EC50 values, for up to 13 weeks, was not associated with mucosal, systemic or reproductive toxicity. Furthermore, long-term (2 years) intravaginal administration of 2% WHI-07 gel-microemulsion was not associated with systemic toxicity or increased carcinogenicity in mice. The improved potency, as well as the lack of mucosal, systemic and reproductive toxicity of WHI-05 and WHI-07, means that these compounds have clinical potential as safe, prophylactic contraceptives in addition to their microbicide activity to curb the sexual transmission of HIV.

Toxicology of progestogens of implantable contraceptives for women.

There are currently four progestogens used in implantable contraceptives marketed or tested in clinical trials: levonorgestrel in Norplant and Jadelle, etonogestrel (3-keto-desogestrel) in Implanon, nestorone in Elcometrine, and nomegestrol acetate in Uniplant and Surplant. Each progestogen was evaluated for hormonal activity and for safety in a wide variety of tests in vitro and in animals prior to their use in women. All four progestogens underwent pre-clinical testing that generally followed the format for animal testing of steroidal contraceptives published by the World Health Organization and the US Food and Drug Administration (FDA). Most of the progestogens have been tested for genotoxicity in bacterial and mammalian cultured cells and in rodents. All were tested for toxicity in short- and long-term toxicology studies in rodents and dogs or monkeys, and all were tested for their effects on reproduction and fetal development. In most cases, the progestogens were tested for carcinogenicity in two rodent species, rats and mice. Early clinical trials in small numbers of women provided additional safety data prior to the exposure of large numbers of women in Phase 3 clinical trials. The published data and data submitted to the FDA demonstrate that the implantable progestogens have no significant or unusual toxicities and have a similar safety profile to the progestogens found in the approved oral contraceptives.

Toxicology of polymers for implant contraceptives for women.

This article reviews the toxicology of polymers that are used in contraceptive implants. The two main classes of synthetic, nondegradable polymers used in the delivery of female contraceptives are silicone elastomers (e.g., Silastic) and ethylene co-vinyl acetate (EVA; ELVAX). The controversies surrounding the silicone breast implants have prompted several studies to evaluate the toxicity of silicones. The epidemiologic data obtained thus far have overwhelmingly concluded that no correlation exists between certain chronic symptoms, such as arthritis, in patients and silicone prosthesis. This conclusion has been echoed by the expert panel report by the Institutes of Medicine. Although the IOM report focused on the safety of silicone breast prosthesis, data emerging from the joint reconstruction area also suggests that Silastic is safe for in vivo use. The toxicological studies on EVA are few, and the conclusion thus far is that they elicit no adverse local or systemic response over extended periods in vivo. In conclusion, the prognosis for Silastic and ELVAX as of now is excellent. However, any future implant development using these polymers should place an emphasis on processing parameters to minimize potential small molecule leachants and establish safety as a function of both site and duration of implantation.

The development and regression of deciduosarcomas and other lesions caused by estrogens and progestins in rabbits.

A series of experiments were conducted to study the histopathological effects of a combination of exogenous estrogens and progestins in mature rabbits. Estradiol (14-45 microg/day) and levonorgestrel (30-233 microg/day) were administered by intravaginal or subdermal Silastic devices for various time intervals to study the development of lesions with time and to determine if lesions regressed following withdrawal of the steroids. The origin of splenic decidual tumors (primary or metastasis from the uterus) was determined by administering the same steroid combination to castrated male rabbits. It was determined that uterine decidualization is present after 7 days of steroid treatment and that neoplasms of decidual cells may appear in the uterus after only 30 days of steroid administration. Decidual changes were observed frequently in uterine arteries, often concurrent with infarct-like areas of necrosis of the uterine wall. Withdrawal of contraceptive steroids for 14-120 days after 60 days' administration resulted in atrophy and disappearance of decidual cells and decidual tumors. Decidual neoplasms developed in the spleen of all castrated male rabbits given subdermal steroids, demonstrating that these tumors can arise as primary neoplasms of the spleen. The foregoing lesions appear to be peculiar to the rabbit and, together with previous data, suggest the rabbit to be a poor model for evaluating the effects of contraceptive steroids in other species.

[Contragestational effects of dihydroartemisinin and artesunate].

In experiments carried out in mice, hamsters, guinea pigs and rabbits both dihydroartemisinin and artesunate showed contragestational effect. In mice and rabbits they caused embryo absorption whereas in hamsters and guinea pigs they induced abortion. The contragestational ED50 of dihydroartemisinin given sc on d 7 of pregnancy in mice and d 5 of pregnancy in hamsters were 32.8(27.7-38.9) mg.kg-1 and 6.1(5.6-6.7) mg.kg-1 respectively. The ED50 of this drug given im on d 18 of pregnancy in guinea pigs was 18.3(13.9-24.2) mg.kg-1. Dihydroartemisinin also showed mid-pregnancy terminating effect in hamsters. The contragestational ED50 of artesunate given sc on d 5 of pregnancy in hamsters and the ED50 of sodium artesunate given sc on d 5-8 of pregnancy in hamsters were 12.2(10.3-14.4) mg.kg-1 and 1.0(0.9-1.2) mg.kg-1 daily respectively. Results of light microscopic examination revealed that dihydroartemisinin was selectively toxic to embryo sac. At dose levels sufficient to induce embryo sac necrosis, dihydroartemisinin did not injure the uterus and ovary of the maternal animals. On the ground of the foregoing observations we consider that dihydroartemisinin, artesunate and their analogous drugs should not be used to treat malaria in pregnant women and there is the possibility to exploit intentional abortion agents from artemisinin derivatives.

Anticoncepción con implantes subdérmicos en mujeres adolescentes: observaciones preliminares en 174 casos

Se presentan resultados de 174 mujeres adolescentes, usuarias de primera vez del Norplant. Se encontró que la edad promedio fue de 17.7 años; 39.9 por ciento eran nulíparas. La tasa acumulada de emabarazos a 2 años fue de 0 por ciento. El 48 por ciento tuvieron ciclos irregulares( 9 por ciento manchando, 20 por ciento sangrando y 19 por ciento amenorrea). Otros efectos adversos reportados fueron: mareos (6 por ciento), cefalea (4 por ciento) y aumento de peso (4 por ciento). La tasa de retiro fue de 6.8 por ciento. Las restantes usuarias están satisfechas con el método. Los anteriores datos nos permiten sugerir el uso del Norplant como método contraceptivo en este etario. Sin embargo, un estudio prolongado (5 años), es necesario para corroborar estos hallazgos

Animal toxicity studies performed for risk assessment of the once-a-month injectable contraceptive Mesigyna.

Results from toxicity studies performed for risk assessment of the combined injectable hormonal preparation Mesigyna are reviewed. Both components of Mesigyna, i.e., estradiol valerate (E2Val) and norethisterone enanthate (NET-EN), have been thoroughly investigated as individual compounds and some limited toxicity data have been obtained for the combination. Most findings which were gathered in these studies from different animal species occurred in the gonads, accessory genital and endocrine organs and can be related to the known species-specific pharmacological activity of a typical estrogen or progestin, respectively. No additional or unexpected information which might indicate a possible estrogen/progestin interaction was gained from the administration of the combined preparation to animals. Based on the results from toxicity testing, there were no objections to the long-term therapeutic use of Mesigyna for hormonal contraception. The predictive value of the effects (including the tumorigenicity) observed in the common laboratory animals with regard to human safety is critically discussed, taking the vast amount of previous experience with hormonal contraceptives into consideration. The conclusion is drawn that there is no animal model for safety assessment of sex steroids that adequately represents the human situation. Quantitative extrapolations from animal toxicity findings to humans, therefore, are not possible. Especially, the value of long-term studies and of toxicity studies on estrogen/progestin combinations is put into question. Like endocrine pharmacology studies, the toxicity studies with these steroid hormones are useful for the characterization of the possible endocrine pharmacological profile only.

PIP: Considerable research has been conducted on the 2 steroid components of the once-a-month injectable contraceptive, Mesigyna. These steroids are estradiol valerate and norethisterone enanthate. Most findings from the limited toxicity studies of the combined injectable in different animal species were limited to the gonads and accessory genital and endocrine organs. The steroids have a toxicological activity profile in each of the species, which indicate that they act as a typical steroidal estrogen or progestin. They are no different than comparable compounds as used in oral contraceptives. Other than these findings, researchers did not acquire any more or unexpected information that would suggest a possible estrogen/progestin interaction from administering the combined preparation to animals. The findings of the toxicity testing do not suggest problems with the long-term use of Mesigyna for hormonal contraception. Yet, the fundamental species differences in endocrinology, metabolism of compounds, and pharmacokinetics make it virtually impossible to quantitatively extrapolate from findings of animal toxicity studies to human, e.g., those on tumorigenicity. A critical review of in vitro and animal toxicity studies of both compounds individually and combined lead to the conclusion that no animal model for safety assessment of sex steroids exists that correctly replicates the human environment. Toxicologists with Schering AG even question the value of long-term studies and toxicity studies on estrogen/progestin combinations. Animal models can be used, however, to characterize a possible endocrine pharmacological profile of newly developed steroids. Any such animal studies need not last any longer than 6 months.