Colon-targeting of progesterone using hybrid polymeric microspheres improves its bioavailability and in vivo biological efficacy.

This study aims to enhance progesterone (PG) oral bioavailability via its incorporation into hybrid colon-targeted pectin/NaCMC microspheres (MS) cross-linked with Zn2+ and Al3+. The MS were characterized for particle morphology, encapsulation efficiency, swelling behavior, drug release, mucoadhesivity and colon-specific degradability. Response-surface methodology was adopted to optimize the fabrication conditions. Enhancement of in vivo drug performance was evaluated through pharmacokinetic and pharmacodynamic studies. The optimized formulation was typically spherical with a mean diameter of 1031 µm and drug entrapment efficiency of 88.8%. This formulation exhibited pH-dependent swelling, negligible drug release in simulated gastric fluid and sustained-release pattern in simulated small intestinal fluid with a mean t50% of 26.5 h. It also showed prolonged and preferential adhesion to rat colonic mucosa, as well as expedited degradation in presence of rat caecal contents. The MS significantly increased the area under the curve and mean residence time by 1.8 and 2.3-fold, respectively compared to the free drug. Orally administered MS showed ~10 times increase in myometrial thickness compared with the drug suspension and elicited uterine responses very similar to that obtained parenterally. These results confirm the ability of this new carrier system to improve the oral bioavailability of PG and attain adequate clinical efficacy.

Administration of progesterone BioRelease LA inhibits follicular growth in llamas (Lama glama) regardless of follicle diameter at the start of treatment.

The aims of the study were twofold: first, the comparison of the pharmacokinetics parameters of two doses of Progesterone BioRelease® LA, (BioRelease Technologies, Lexington, KY, USA) one of 300 mg and other of 150 mg and their effects on ovarian dynamics in llamas. Based on the results from the first study, the aim of the second study was to evaluate the effect of the doses of 150 mg of progesterone on follicular activity considering the stage of the largest follicle at the beginning of treatment. The results in Study 1 showed that both doses of the formulation induced plasma progesterone concentrations higher than 1 ng/ml during the first 6 days of treatment in all females, progesterone concentrations steadily decline until Day 5 following by a slowly decrease. The total amount of progesterone released during treatment was higher in Group 300 than in Group 150 (p = 0.045). Mean maximum concentrations were 14.9 ± 2.24 and 14.3 ± 2.16 ng/ml for Group A versus Group B (p = 0.58), and they were registered on Day 1.5 ± 0.22 and 1.7 ± 0.34 days, respectively (p = 0.10). None of the animals of Group A showed progesterone concentration below 1 ng/ml during all studied period. The treatment applied in Study 2 was efficient in inhibiting the ovarian follicular dynamics and to start a superestimulatory treatment. The use of progesterone Biorelease® LA of 150 mg in comparison with the dose of 300 mg could be more effective in the use of synchronization protocols in llamas for AI or prior to the application of an ovarian superstimulatory treatment.

Amidated pectin/sodium carboxymethylcellulose microspheres as a new carrier for colonic drug targeting: Development and optimization by factorial design.

The colon is a promising site for drug targeting owing to its long transit time and mild proteolytic activity. The aim of this study was to prepare new low methoxy amidated pectin/NaCMC microspheres cross-linked by a mixture of Zn(2+) and Al(3+) ions and test their potential for colonic targeting of progesterone. A 2(4) factorial design was carried out to optimize the preparation conditions. High drug entrapment efficiency (82-99%) was obtained and it increased with increasing drug concentration but decreased with increasing polymer concentration. Drug release rate was directly proportional to the microsphere drug content and inversely related to Al(3+) ion concentration. Drug release was minimal during the first 3h but was significantly improved in the presence of 1% rat caecal contents, confirming the microsphere potential for colonic delivery. The microspheres achieved >2.3-fold enhancement of colonic progesterone permeability. These results confirm the viability of the produced microspheres as colon-targeted drug delivery vehicle.

Beads made of cyclodextrin and oil for the oral delivery of lipophilic drugs: in vitro studies in simulated gastro-intestinal fluids.

The aim of this work was to investigate the stability in vitro, in simulated gastro-intestinal fluids, of beads, made of α-cyclodextrin and soybean oil, and to study the release of progesterone, a model of lipophilic drug. This was evaluated over time by the monitoring of the proportion of intact beads, their volume and the percentage of progesterone dissolved. Their incubation in the simulated gastric fluid provoked a moderate reduction of their number (20%) and a decrease of their volume (50%) after 55 min. Whatever the intestinal medium subsequently introduced, bead number and volume decreased more until bead disintegration that appeared faster in sodium taurocholate rich-medium. In such fluid, the amount of progesterone dissolved increased rapidly between 65 and 180 min, with both beads and emulsion to be equal after 85 min. With soft capsules, the increase was more gradual. In sodium taurocholate free-medium, more progesterone was dissolved from the emulsion than from beads or soft capsules. The release of progesterone from beads resulted from the erosion of their matrix and its partition equilibrium between oily micro-droplets and aqueous phase. The original structure of beads confers to this multiparticulate system interesting properties for the oral delivery of lipophilic drugs.

Brain distribution and behavioral effects of progesterone and pregnenolone after intranasal or intravenous administration.

Neurosteroids hold great promise for the treatment of diseases of the central nervous system (CNS). We compared the uptake by 11 brain regions and appearance in blood of tritium-labeled pregnenolone and progesterone after intranasal and intravenous (IV) injection. Both neurosteroids appeared in blood and brain after either method of administration, but with important differences in uptake. Bioavailability based on appearance in arterial serum showed that about 23% and 14% of the intranasal administered doses of pregnenolone and progesterone, respectively, entered the blood. Brain levels were about two fold lower after intranasal administration for the two neurosteroids. With intranasal administration, brain levels of the two steroids did not vary over time (2-120 min), whereas brain levels were higher early (10 min or less) after i.v. administration. With i.v. administration, uptake by brain regions did not vary, whereas the olfactory bulb, hippocampus, and hypothalamus had high uptake rates after intranasal administration. Intranasal administration of prenenolone improved memory, whereas progesterone decreased anxiety, thus demonstrating that therapeutic levels of neurosteroids can be delivered to the brain by intranasal administration. The neurosteroids were rapidly degraded after i.v. or intranasal delivery, but pregnenolone was more resistant to degradation in the brain after intranasal administration and in serum after i.v. administration. These results show that either the i.v. or intranasal routes of administration can deliver neurosteroids to blood and brain, but that the two routes have significant differences with intranasal administration favoring some brain regions.

Progesterone bioavailability with a progesterone-releasing silicone vaginal ring in IVF candidates.

A vaginal ring made of silicone polymers and barium sulfate, and containing 1 g of pure micronized progesterone, was developed for luteal supplementation in women undergoing cycles of in vitro fertilization (IVF). The ring, modeled on the Estring, was designed as a means of providing continuous intravaginal delivery of progesterone. Bioavailability of progesterone in the blood was demonstrated for 24 hours in IVF candidates who had an endogenous progesterone deficiency after treatment with gonadotropin-releasing hormone (GnRH) analogues. After the first 4 h of increasing release of progesterone from the ring (with mean serum levels of 1.39 +/- 0.8 ng/ml after 4 h), only a slight increase in serum progesterone levels (with a mean peak of 1.5 +/- 0.45 ng/ml after 24 h) was observed during the rest of the test period. Gonadotropin levels were not affected after insertion of the ring. The ring was well tolerated by the patients. The maximum serum progesterone level was lower in comparison with other forms of progesterone application, but it should be sufficiently high, due to the uterine first-pass effect. This study demonstrated that progesterone administration through a silicone ring for luteal support is feasible in IVF treatment. As the vaginal ring is very well tolerated by the patients, these findings may encourage the pharmaceutical industry to design an appropriate progesterone ring for luteal support.

Development and in vitro evaluation of a mucoadhesive vaginal delivery system for progesterone.

The purpose of the present study was to design a novel carrier system based on a mucoadhesive polymer exhibiting improved properties concerning drug delivery to the vaginal mucosa. This was reached by the covalent attachment of L-cysteine to commercially available polyacrylic acid (Carbopol 974P). Mediated by a carbodiimide, increasing amounts of L-cysteine were covalently linked to the polymer. The resulting thiolated polyacrylic acid conjugates (NaC974P-Cys) displayed between 24.8 and 45.8 micromol thiol groups per gram of polymer. Because of the formation of intra- and/or intermolecular disulfide bonds, the viscosity of an aqueous thiolated polymer gel (3%) increased about 50% at pH 7.0 within 1 h. In oscillatory rheological measurements, it was shown that this increase in viscosity is mainly due to the increase in elasticity. Tensile studies carried out on freshly excised cow vagina demonstrated a significant (P<0.05) increase in the total work of adhesion (TWA) compared to the unmodified polymer. An amount of 24.8 micromol thiol groups per gram of polymer resulted in a 1.45-fold increase in the TWA, whereas an amount of 45.8 micromol showed an even 2.28-fold increase. These improved mucoadhesive properties can be explained by the formation of disulfide bonds between the thiolated polymer and cysteine rich subdomaines of the mucus layer. The release rate of the model drug progesterone from tablets based on microcrystalline cellulose serving as the reference was approximately 1% per hour, whereas it was 0.58% per hour for the unmodified polymer (NaC974P) and 0.12% per hour for the thiolated polymer (NaC974P-Cys). Therefore, this thiolated polymer is a promising carrier for progesterone providing a prolonged residence time and a controlled drug release.

Management of the extremely preterm infant: is the replacement of estradiol and progesterone beneficial?

This review presents data to suggest that postnatal estradiol and progesterone replacement therapy may be beneficial in preterm infants. During pregnancy, maternal plasma levels of estradiol and progesterone increase up to 100-fold compared to the nonpregnant status. The fetus is also exposed to these increasing hormone levels. After delivery, estradiol and progesterone levels drop by a factor of 100 within 1 day. Whereas this is a physiological condition for an infant born at term, preterm delivery means withdrawal from the placental supply of these hormones at an earlier developmental stage. Seventy years ago, the idea was raised that preterm infants may benefit from the replacement of estrogens. Studies in which estrogen was injected subcutaneously showed only a slightly better bodyweight gain compared to placebo-treated controls and therefore routine use was not established. The effective treatment of postmenopausal osteoporosis with hormone replacement therapy led to a pilot study of estradiol and progesterone therapy to prevent osteopenia of prematurity. The highest median bone mineral accretion rate was found in the replacement group when the supplementation with calcium and phosphorus was also sufficient. None of the previous studies dealing with estrogen replacement controlled for achieved plasma levels of estradiol in the infants. In our controlled randomised pilot study with 30 preterm infants (15 in each group), we aimed to maintain intra-uterine plasma levels of estradiol and progesterone. Preterm infants with replacement of estradiol and progesterone for 6 weeks postnatally showed trends to higher bone mineral accumulation. In addition, a trend towards a lower incidence of chronic lung disease was found. Neurodevelopmental follow-up showed normal psychomotor development in infants given estradiol and progesterone, whereas the untreated infants (controls) showed a trend towards delayed development. Recent research emphasises that estradiol and progesterone may be important for brain development. Thus, while there is data indicating that postnatal estradiol and progesterone replacement therapy may be beneficial in preterm infants, experience with this new therapy is limited and extensive research is needed to address the potential benefits and to rule out adverse effects.

Progesterone administration by nasal spray in menopausal women: comparison between two different spray formulations.

The aim of the study was to compare the bioavailability of progesterone dissolved in almond oil or dimethicone, and administered by nasal spray. Twenty healthy menopausal women were randomly allocated to treatment by four doses of intranasal spray either of a progesterone solution in almond oil, 2 mg/0.1 ml, corresponding to a total dose of approximately 11 mg of progesterone, or a progesterone solution in dimethicone 5 mg/0.1 ml corresponding to a total dose of approximately 28 mg of progesterone. Circulating progesterone levels were calculated at various time intervals following administration. The formulation with almond oil yielded a maximum progesterone concentration (Cmax of 3.75 ng/ml at Tmax = 60 min, and the area under the curve (AUC0-720) value was 1481.6 +/- 343. The formulation with dimethicone yielded a mean Cmax of 1.049 ng/ml at Tmax = 30 min; the AUC0-720 value was 302.06 +/- 37.5. Therefore, bioavailability of progesterone dissolved in almond oil proved to be largely superior compared to the solution in dimethicone. The crucial role of the carrier in the spray formulations is discussed; in addition to ensuring clinical safety, it must have good solubility for progesterone, be fluid enough to enable efficient 'spraying' and also must allow progesterone to be absorbed through the nasal mucosa.

Contraception with progestogens and progesterone during lactation.

The growth and development of breastfed infants whose mothers used the contraceptive implants Norplant containing levonorgestrel and the injectable containing norethisterone enanthate were studied. Each group comprised of 120 women who initiated the use during the 5th to 7th week postpartum and were compared with a similar number of IUD using mothers. The breastfeeding performance did not differ between groups. The infants of the three groups performed similarly as regards their physical growth and health as well as the time of acquisition of the various milestones of psychomental development. A vaginal ring releasing 10 mg of the "natural" progesterone per 24 h was tested in breastfeeding mothers. The continuous use of the ring produced a serum level of progesterone around 4 ng/ml. This was effective in augmenting lactational infertility even through the later phases of breastfeeding when such an effect starts to wane off. The use of the ring proved to be acceptable and had no ill-effect on breastfeeding or infant growth or health. Using the natural progesterone as a contraceptive adds a new measure of safety, since the amount of the steroid secreted in the mother's milk will not be effectively absorbed from the infant's gut. These studies suggest the possibility of using two new methods for breastfeeding mothers; Norplant and the progesterone vaginal contraceptive ring. These can be initiated early postpartum, whenever this is considered needed.

PIP: Weight gain and psychomotor development of breastfed infants of Egyptian mothers using Norplant, Cu T-380A IUDs, norethisterone enanthate injectables (NET-EN), Depo Provera and a levonorgestrel minipill were compared in 2 trials. First, groups of 120 women using Norplant and NET-EN were compared to a control group using IUDs, beginning 5-7 weeks postpartum. There were no differences in infant weight gain, mid-arm circumference, triceps-skin-fold thickness, or timing of motor milestones. The mean growth curve of all 3 groups were close to that of the 50th percentile for Egyptian infants. While timing of initiation of supplements was similar in the 3 groups, complete weaning occurred first in the IUD group, second in the Norplant group, and last in the NET-EN users. A second trail compared progesterone implants injected with a trocar that resulted in a blood level of 3 ng/ml for 5 months, with Population Council vaginal rings releasing 10 progesterone/24 hours, and CuT-380A IUDs. Serum progesterone in the ring users averaged 5.2 ng/ml for the 1st 2 weeks, then leveled off at about 4 ng/ml for about 2 months, falling to about 3 ng/ml for the last 3 weeks of use. Each women used 4 rings per year. Evidence of ovulation by ultrasonic vaginal probe and assay of estradiol and progesterone was apparent in 25% of vaginal ring users, compared to 55.9% of controls in the 2nd 6 months postpartum. There was 1 pregnancy in a ring users. The continuation rates were 66.6% for rings and 85.5% for IUDs. The reasons for discontinuation in vaginal ring continuation were logistical problems and unfamiliarity.

Autoradiographic localization of [3H]RU 486 and [3H]progesterone in the uterus, pituitary and hypothalamus of the rat.

Twenty-one castrated oestrogen-primed Wistar rats, which were 2-months-old, were injected via the jugular vein with 100 mu Ci/100 g body weight of [3H]RU 486 or [3H]progesterone. Some of these received unlabelled compounds for competition studies. Samples of reproductive tract, pituitary and hypothalamus were excised after 15 min. The 4-microns frozen sections were processed for thaw-mounted autoradiography. The exposure time of the autoradiogram was approximately 6 months. After the injection of [3H]RU 486 and [3H]progesterone, the nuclear concentration of radioactivity was most distinct in muscular and stromal cells of the uterus, and the epithelial nuclei of lumina and glands showed weak labelling. Nuclear localization was also observed in muscle cells of the vagina, cervix and oviduct. After injection of [3H]progesterone, the radioactivity was found in the nuclei and cytoplasm of anterior pituitary cells and some cells showed a preferential nuclear concentration of radioactivity. The distribution of [3H]RU 486 in the anterior pituitary was more extensive than that of [3H]progesterone. In the hypothalamus, specific localization of [3H]RU 486 and [3H]progesterone existed in neurones accumulated in the preoptic nucleus, preoptic suprachiasmatic nucleus and the periventricular nucleus. No localization was found in the diaphragm. Pretreatment with RU 486, but not with dexamethasone, reduced the nuclear concentration of radioactivity of [3H]progesterone in the vagina, uterus, oviduct, pituitary and hypothalamus. The nuclear concentration of radioactivity after injection of [3H]RU 486 was also decreased by preinjection with progesterone. The autoradiographic results suggest that RU 486 and progesterone competed for the specific binding site (possibly a progesterone receptor) in the target cells at the levels of the uterus, pituitary and hypothalamus in vivo.

Serum disposition of exogenous progesterone after intramuscular administration in bitches.

Progesterone was administered IM to 6 adult anestrous bitches at a dosage of 2 mg/kg of body weight. Serum progesterone concentrations were measured prior to progesterone administration and for 72 hours thereafter. The serum progesterone concentration time data were analyzed by use of a pharmacokinetics modeling computer program. The mean (+/- SD) peak serum progesterone concentration (34.3 +/- 7.8 ng/ml) was reached at 1.8 +/- 0.2 hours after progesterone administration. The mean serum progesterone concentration was 6.9 +/- 1.4 ng/ml at 24 hours and 2.0 +/- 0.4 ng/ml at 48 hours after progesterone administration. By 72 hours after administration, mean serum progesterone concentration was 0.9 +/- 0.2 ng/ml, which was comparable to serum progesterone concentrations prior to injection. The mean half-life of the absorption phase was 0.5 hours (range, 0.3 to 0.7 hours). The mean half-life of elimination was 12.1 hours (range, 9.5 to 13.8 hours). By analysis of the data, it was established that a dosage of 3 mg/kg, when the hormone was given IM to dogs once a day, would maintain serum progesterone concentration greater than 10 ng/ml.

Autoradiographic localization of [3H]RU 486 and [3H]progesterone in the uterus, pituitary and hypothalamus of the rat.

Twenty-one castrated oestrogen-primed Wistar rats, which were 2-months-old, were injected via the jugular vein with 100 microCi/100 g body weight of [3H]RU 486 or [3H]progesterone. Some of these received unlabelled compounds for competition studies. Samples of reproductive tract, pituitary and hypothalamus were excised after 15 min. The 4-micron frozen sections were processed for thaw-mounted autoradiography. The exposure time of the autoradiogram was approximately 6 months. After the injection of [3H]RU 486 and [3H]progesterone, the nuclear concentration of radioactivity was most distinct in muscular and stromal cells of the uterus, and the epithelial nuclei of lumina and glands showed weak labelling. Nuclear localization was also observed in muscle cells of the vagina, cervix and oviduct. After injection of [3H]progesterone, the radioactivity was found in the nuclei and cytoplasm of anterior pituitary cells and some cells showed a preferential nuclear concentration of radioactivity. The distribution of [3H]RU 486 in the anterior pituitary was more extensive than that of [3H]progesterone. In the hypothalamus, specific localization of [3H]RU 486 and [3H]progesterone existed in neurones accumulated in the preoptic nucleus, preoptic suprachiasmatic nucleus and the periventricular nucleus. No localization was found in the diaphragm. Pretreatment with RU 486, but not with dexamethasone, reduced the nuclear concentration of radioactivity of [3H]progesterone in the vagina, uterus, oviduct, pituitary and hypothalamus. The nuclear concentration of radioactivity after injection of [3H]RU 486 was also decreased by preinjection with progesterone. The autoradiographic results suggest that RU 486 and progesterone competed for the specific binding site (possibly a progesterone receptor) in the target cells at the levels of the uterus, pituitary and hypothalamus in vivo.