Sustained-release hormonal preparations XV: release of progesterone from cholesterol pellets in vivo

Single neonatal estrogen implant sterilizes female animals by decreasing hypothalamic KISS1 expression

Reproductive sterilization by surgical gonadectomy is strongly advocated to help manage animal populations, especially domesticated pets, and to prevent reproductive behaviors and diseases. This study explored the use of a single-injection method to induce sterility in female animals as an alternative to surgical ovariohysterectomy. The idea was based on our recent finding that repetitive daily injection of estrogen into neonatal rats disrupted hypothalamic expression of Kisspeptin (KISS1), the neuropeptide that triggers and regulates pulsatile secretion of GnRH. Neonatal female rats were dosed with estradiol benzoate (EB) either by daily injections for 11 days or by subcutaneous implantation of an EB-containing silicone capsule designed to release EB over 2-3 weeks. Rats treated by either method did not exhibit estrous cyclicity, were anovulatory, and became infertile. The EB-treated rats had fewer hypothalamic Kisspeptin neurons, but the GnRH-LH axis remained responsive to Kisspeptin stimulation. Because it would be desirable to use a biodegradable carrier that is also easier to handle, an injectable EB carrier was developed from PLGA microspheres to provide pharmacokinetics comparable to the EB-containing silicone capsule. A single neonatal injection of EB-microspheres at an equivalent dosage resulted in sterility in the female rat. In neonatal female Beagle dogs, implantation of an EB-containing silicone capsule also reduced ovarian follicle development and significantly inhibited KISS1 expression in the hypothalamus. None of the treatments produced any concerning health effects, other than infertility. Therefore, further development of this technology for sterilization in domestic female animals, such as dogs and cats is worthy of investigation.

Cocrystallization of Progesterone with Nitrogen Heterocyclic Compounds: Synthesis, Characterization, Calculation and Property Evaluation

Progesterone injection is oily because of its poor solubility. It is necessary to develop new dosage forms or delivery methods for Progesterone. Six cocrystals of Progesterone with nitrogen heterocyclic compounds (2,6-diaminopyridine, isonicotinamide, 4-aminopyridine, aminopyrazine, picolinamide and pyrazinamide) have been designed and prepared by ethyl acetate-assisted grinding, of which four cocrystals (2,6-diaminopyridine, isonicotinamide, 4-aminopyridine and aminopyrazine) had single crystal data in 1:1 stoichiometry. Metadynamics-genetic crossing was used to search and optimize various cluster structures to explain the reason the other two cocrystals could not be obtained with suitable size for single crystal X-ray diffraction. In contrast to the carboxyl group, the amide group and amino group were good substituents in the pyridine/pyrazine ring for cocrystallization with Progesterone, which meant inductive effect played an important role in nitrogen heterocyclic compounds containing reactive hydrogen. All cocrystals were more soluble than Progesterone in water, and Progesterone-pyrazinamide cocystal featured the best water solubility performance with an approximately six-fold increase over free Progesterone. This successful attempt provides an effective route for designing and manufacturing novel solid states of Progesterone.

Critical Analysis on Characterization, Systemic Effect, and Therapeutic Potential of Beta-Sitosterol: A Plant-Derived Orphan Phytosterol

Beta-sitosterol (BS) is a phytosterol, widely distributed throughout the plant kingdom and known to be involved in the stabilization of cell membranes. To compile the sources, physical and chemical properties, spectral and chromatographic analytical methods, synthesis, systemic effects, pharmacokinetics, therapeutic potentials, toxicity, drug delivery and finally, to suggest future research with BS, classical as well as on-line literature were studied. Classical literature includes classical books on ethnomedicine and phytochemistry, and the electronic search included Pubmed, SciFinder, Scopus, the Web of Science, Google Scholar, and others. BS could be obtained from different plants, but the total biosynthetic pathway, as well as its exact physiological and structural function in plants, have not been fully understood. Different pharmacological effects have been studied, but most of the mechanisms of action have not been studied in detail. Clinical trials with BS have shown beneficial effects in different diseases, but long-term study results are not available. These have contributed to its current status as an "orphan phytosterol". Therefore, extensive research regarding its effect at cellular and molecular level in humans as well as addressing the claims made by commercial manufacturers such as the cholesterol lowering ability, immunological activity etc. are highly recommended.

Beta-Sitosterol: A Promising but Orphan Nutraceutical to Fight Against Cancer

All the currently available cancer therapeutic options are expensive but none of them are safe. However, traditional plant-derived medicines or compounds are relatively safe. One widely known such compound is beta-sitosterol (BS), a plant derived nutrient with anticancer properties against breast cancer, prostate cancer, colon cancer, lung cancer, stomach cancer, ovarian cancer, and leukemia. Studies have shown that BS interfere with multiple cell signaling pathways, including cell cycle, apoptosis, proliferation, survival, invasion, angiogenesis, metastasis and inflammation. Most of the studies are incomplete partly due to the fact that BS is relatively less potent. But the fact that it is generally considered as nontoxic, the opposite of all currently available cancer chemo-therapeutics, is missed by almost all research communities. To offset the lower efficacy of BS, designing BS delivery for "cancer cell specific" therapy hold huge potential. Delivery of BS through liposome is one of such demonstrations that has shown to be highly promising. But further research did not progress neither in the field of drug delivery of BS nor in the field on how BS mediated anticancer activities could be improved, thus making BS an orphan nutraceutical. Therefore, extensive research with BS as potent anticancer nutraceutical is highly recommended.

Absorption of oral ethinylestradiol is delayed by its eutectic mixture with cholesterol

A solid dispersion of ethinylestradiol-cholesterol (EE & CHOL; eutectic 1:4 W/W) was prepared by melting and rapid cooling. The fused material was then mixed with lactose as vehicle. Soft gelatin capsules were filled with 50 mg of the final mixture to give 0.050 mg of ethinylestradiol. Six female volunteers received, one capsule of the eutectic combination of EE:CHOL or one 50 micrograms tablet of ethinylestradiol (Dianor, Syntex), in a cross-over study and in fasting state. Venous blood samples were drawn at 0, 10, 20, 30, 40, 50, 60, 90, 120, 240, 360, 480, 720, 1440 minutes after dosing. Immunoreactive EE was measured by radioimmunoassay to assess the serum concentration-time course. All subjects exhibited a significant increase in EE levels after oral administration. Mean peak EE levels, 1350 pg/ml vs 91 pg/ml (p less than 0.001), were achieved 360 minutes and 90 minutes (p less than 0.01), after administration of the eutectic and reference formulation, respectively. Eutectic mixture showed a greater area under the serum concentration-time curve, longer mean residence time of the drug in the body, and four times the value of the elimination half-life of the reference formulation. It is concluded that the combination of ethinylestradiol with cholesterol forming an eutectic mixture, when administered orally to normal women, modulates the absorption and the bioavailability of the EE. This approach may be suitable for long-acting oral treatment with sex steroids.

Compressed poly(vinyl alcohol)-polycaprolactone admixture as a model to evaluate erodible implants for sustained drug delivery

An implant may release a drug either by diffusion concurrent with dissolution of the polymeric implant material without depolymerization (Type A) or by bioerosion involving depolymerization (Type B). The Type A material may induce immune response, while the erosion of Type B polymer releases fragments which could cause toxicity problems. It is proposed that a combination of the two types of polymers may attenuate the intensity of immune response and toxicity, because the presence of one in an implant of the same weight reduces the amount of the other. However, it is important to determine first, if sustained delivery may be achieved by such an implant. In this study, partially hydrolyzed poly(vinyl acetate) (PVA) and polycaprolactone (PCL) were chosen as the model Type A, and B polymers, respectively, to evaluate this objective in vitro. Pellet discs were prepared to assess the effects of compression, proportion of PVA to PCL, acetyl content of PVA, PCL hydrolysis catalyst and drug loading, using methylene blue (MB) as a model drug. Results showed that sustained delivery could be effected, but PCL erosion did not occur as planned. Therefore, PCL served only as a passive component of the implant, while PVA was eroded with the release of MB. Consequently, it was inferred that a polymer may not be required as a passive component, which suggested the use of other compounds of known biocompatibility. Tests with insulin in a compressed solid admixture with cholesterol showed that reduction of hyperglycemia in diabetic Wistar rat could be effected reproducibly for at least 2 weeks. Thus, the present study, originally planned to test a proposed concept, indicates that many nonpolymeric materials of known biocompatibility may be suitable for drug delivery implants as well.

Norethisterone-cholesterol eutectic mixture as an oral sustained-release hormonal preparation: bioequivalence study in humans

A solid dispersion of norethisterone and cholesterol (NET:CHOL; eutectic 1:4 w/w) was prepared by melting and rapid cooling. The fused material was then mixed with lactose as vehicle. Soft gelatin capsules were filled with 55 mg of the final mixture to give 0.35 mg of NET. One control formulation prepared with fused NET and lactose (NET:LAC) was capsuled with the same NET dosage, and one commercial tablet (Dianor, Syntex) with 0.35 mg NET were used as reference formulations. In a cross-over study, five female volunteers received, one month apart, in fasting state, each one of the three formulations. Blood samples were drawn at O,O.5,1,1.5,2,4,8,12,24 and 36 hours after dosing. Immunoreactive plasma NET was measured by RIA to assess pharmacokinetic parameters. The NET:CHOL formulation showed a greater area under the serum concentration-time curve, lower peak concentrations and a smaller release rate constant as compared to the reference preparations. It is concluded that the NET:CHOL eutectic mixture is a modified release dosage form and a sound approach in regulating the drug access rate to the body's central compartment.

In vivo release of testosterone from vinyl polymer composites prepared by radiation-induced polymerization

Polymer-testosterone composites with long periods of controlled slow release were made by radiation-induced polymerization in a supercooled state at low temperature using glass-forming monomers. The in vitro release of testosterone from various vinyl polymer composites was found to follow a matrix-controlled process (Q-t1/2). The rate of drug delivery was accelerated with increasing water content of polymers. In experiments in vivo, the composites were implanted subcutaneously in the back of castrated rats during the 30 day test period. The in vivo release rate of testosterone was a little smaller than in vitro. This difference between two releases also increased with the increase of hydrophilicity of polymer. The physiological response in rats was investigated by measuring the weight of ventral prostate and serum testosterone concentration with testosterone-containing composites. The weight of ventral prostate increased linearly with increasing rate of drug release and the serum testosterone concentration could be correlated with the release and with the weight increase of ventral prostate. It was found from microscopic observation that the used polymer carriers had relatively good biocompatibility to cause little foreign body reaction.

Controlled release of biologically active compounds from bioerodible polymers

This article reviews the controlled release of biologically active agents by the erosion or chemical degradation of a polymer matrix into which the agent is incorporated. Chemically bound active agents and work on steroid release from cholesterol implants are not covered. The mechanisms of polymer erosion discussed are: cross-linked scission; hydrolysis, ionization or protonation of pendant groups; backbone cleavage. Drug release studies are dealt with under each of these headings.