Derivatives of phosphonate and vinyl phosphate analogs of D-ribose 5-phosphate.
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Chemical Phenomena↗
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Effects of the etonogestrel-releasing contraceptive implant (Implanon on parameters of breastfeeding compared to those of an intrauterine device.
Eighty healthy single births born at a gestational age of 259-294 days were studied in an open, non-randomized, group comparative fashion. The mothers were on average 6 weeks postpartum, healthy, and fully breastfeeding at the start of treatment. Forty-two mothers elected to use the etonogestrel-releasing implant, Implanon, while 38 chose use of a non-hormone medicated intrauterine device (IUD). One month after implant placement, the dose of etonogestrel ingested by the infants via breast milk was 19.86 ng/kg/day, which decreased to 10.45 ng/kg/day at the end of the study period (month 4). The volume of breast milk production was not affected by the use of Implanon. There were no significant differences between groups in milk content of total fat, total protein, and lactose. The timing and quantity of supplementary feedings did not differ between the two groups. Growth of the infants was analyzed by treatment and gender. For the girls, no differences between groups were seen for body weight, body length, and head circumference. The same applied to the boys except for a somewhat larger, although not statistically significant, increase in body weight for boys whose mother used Implanon. There was a low incidence of intercurrent illnesses in the infants of both groups. None of the conditions was of a serious nature. From the present study, we conclude that Implanon did not change the volume and composition of breast milk. The low concentration of etonogestrel ingested by the infant was not associated with adverse effects.
Adult↗
Effect of Implanon use on selected parameters of thyroid and adrenal function.
In this article, the effects of Implanon implant use on thyroid and adrenal function was compared with those of Norplant implants. In this 2-year open randomized study of 80 implant acceptors, we found that both implants may induce minimal changes in thyroid hormones and cortisol levels, possibly secondary to alterations in the respective binding globulins in the serum. These alterations in thyroid and adrenal function would have no clinical significance in healthy women. In the Norplant group, sex hormone-binding globulin levels decreased, whereas increased levels were found in the Implanon users at the end of 2 years. These findings lend support to the fact that etonogestrel, released from Implanon implants, is significantly less androgenic than levonorgestrel, released from the Norplant implants.
Adrenal Cortex↗
Implanon contraceptive implants: effects on carbohydrate metabolism.
The objective of the study was to assess the possible differences in effects of Implanon and Norplant implants on carbohydrate metabolism. This is a 2-year open randomized study of 80 implant (Implanon and Norplant) acceptors. Oral glucose tolerance test (OGTT) was performed before implant insertion and at 6, 12, and 24 months after implant insertion. Glycosylated hemoglobin A(1)C was measured in fasting samples and plasma samples during OGTT were tested for glucose and insulin levels. There was a significant increase in the area under the curve for both glucose and insulin during OGTT within each group with increasing duration of use. However, there was no significant change in the fasting plasma glucose values. There was no significant difference in the carbohydrate parameters between the two groups during implant use, except for a minimal but statistically significant rise in fasting glycosylated hemoglobin A(1)C levels at 24 months in the Implanon group. Both implants appear to induce mild insulin resistance but no significant change in serum glucose levels. These alterations in carbohydrate metabolism should have no clinical significance in healthy women.
Adolescent↗
Nonpalpable ultrasonographically not detectable Implanon rods can be localized by magnetic resonance imaging.
Recently, the contraceptive implant Implanon has been introduced in several European countries. In comparison to the six-capsule preparation Norplant, the removal of this single-rod system should be associated with less complications. However, the removal of nonpalpable Implanon rods can be difficult because the implant is not always visible with ultrasound. The aim of this study was to find a radiologic method for the localization of Implanon implants that are nonpalpable and can not be detected by ultrasound. X-ray, ultrasound, computed tomography, and magnetic resonance imaging (MRI) were investigated as methods to localize Implanon in a pig chest preparation and in a woman with a nonpalpable implant. The implant in the woman could be localized unequivocally only by MRI. We conclude that MRI is the best method for the unequivocal localization of nonpalpable, ultrasonographically not detectable Implanon rods. To avoid unnecessary scar tissue formation, it may be appropriate to defer surgery for the removal until definitive localization.
Animals↗
Implantable contraceptives for women.
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Contraceptive Agents, Female↗
Investigation of a novel preparation of testosterone decanoate in men: pharmacokinetics and spermatogenic suppression with etonogestrel implants.
We have investigated the pharmacokinetics and effects on the male reproductive axis of a novel preparation of testosterone decanoate (TD) with a progestogen implant. Twenty healthy Chinese men were administered TD (400 mg intramuscular 4 weekly) with two subcutaneous (SC) etonogestrel implants. Trough testosterone concentrations rose with repeated administration. Peak concentrations 1 week after the fourth injection were 31 +/- 2 nmol/liter. Both LH and FSH were rapidly suppressed and continued to fall during treatment. Spermatogenesis was also suppressed, to <or=1 x 10(6)/mL in all men with 16 (80%) azoospermic at 12 weeks. Treatment was associated with an increase in weight, and also increases in hemoglobin concentration (9%) and hematocrit (15%). No subjects withdrew from the study, although the study was terminated after subjects had completed 12 to 18 weeks as some men were found to have elevated liver enzyme tests. These data demonstrate that the pharmacokinetics of TD are improved compared to previous injectable testosterone preparations, although peak testosterone concentrations rise briefly into the supraphysiological range. The speed and degree of spermatogenic suppression suggest that this combination has promise as an effective male contraceptive.
Adult↗
The combined contraceptive vaginal ring, NuvaRing: an international study of user acceptability.
The acceptability of the combined contraceptive vaginal ring, NuvaRing, was assessed during two trials conducted in North America and Europe. Women completed a questionnaire about the ring's clarity of instructions, ease of use, sexual comfort, cycle-related characteristics and satisfaction after 3, 6 and 13 cycles of use. A total of 1,950 women (82% of those recruited) completed a questionnaire at cycle 3. At baseline, 66% of participants preferred oral contraceptives, but after three cycles of ring use 81% preferred the ring. On study completion, 97% agreed that the instructions for use were clear; 85% of women and 71% of their partners never/rarely felt the ring during intercourse and 94% of partners never/rarely minded that the woman was using the ring. Overall acceptance was high, 96% were satisfied with the ring and 97% would recommend the ring. Similar responses were seen for women who prematurely discontinued from the studies, except that slightly fewer women were satisfied (60%) and would recommend the ring (75%). Reasons for liking the ring included 'not having to remember anything' (45%) and 'ease of use' (27%). In conclusion, there is a high level of user and partner acceptability for the contraceptive ring.
Adolescent↗
The combined contraceptive ring NuvaRing and spermicide co-medication.
The effects of nonoxynol-9 on etonogestrel and ethinylestradiol release and absorption from NuvaRing were studied in 12 subjects for two cycles: one control and one interaction cycle (nonoxynol-9 was administered on day 8). Nonoxynol-9 had no effect on release or absorption and, consequently, serum levels. Therefore, nonoxynol-9 did not compromise the contraceptive efficacy of NuvaRing.
Administration, Intravaginal↗
Effects on the hemostatic system and liver function in relation to Implanon and Norplant. A prospective randomized clinical trial.
In this prospective randomized clinical trial, two long-term contraceptive implants were studied with respect to hemostasis and liver function in 86 healthy young women. The two implants used were Implanon, containing the progestagen etonogestrel (the biologically active metabolite of desogestrel) and Norplant, the implant containing the progestagen levonorgestrel. The results of the trial showed that both implants had similar small effects on the hemostatic system that are not suggestive of a tendency towards thrombosis. The effect on liver function was characterized by increases in total bilirubin and gamma-glutamyl transferase and decreases in alanine aminotransferase and aspartate aminotransferase.
Adult↗
Twenty-four month comparison of apolipoproteins A-1, A-II and B in contraceptive implant users (Norplant and Implanon) in Birmingham, United Kingdom.
A 2-year prospective, randomized study of 60 implant users was performed to evaluate fasting serial serum apolipoprotein A-I, A-II, and B levels before insertion and every 3 months in users of two contraceptive implants releasing levonorgestrel (Norplant) and 3-ketodesogestrel/etonogestrel (Implanon) in Birmingham, United Kingdom. All changes in serum apolipoprotein concentrations, irrespective of an increase or decrease, were smaller than one standard deviation of the mean concentration at baseline and did not exceed the normal range for the laboratory, thus implying no evidence of an increased risk of coronary heart disease.
Adolescent↗
Pharmacokinetics of etonogestrel released from the contraceptive implant Implanon.
Eight healthy women between 22 and 40 years of age participated in this prospective open study of 2 years' duration. Either on or between days 1 to 7 of a spontaneous menses, an intravenous bolus dose of 150 micrograms etonogestrel (3-ketodesogestrel) was given. During days 1-5 of a subsequent spontaneous cycle, the single-rod contraceptive implant (Implanon) was inserted in the upper arm of the volunteer. One year after placement of the implant, another intravenous bolus dose was given (implant in place), and a third bolus dose was given after 2 years, with the implant removed. Frequent serum sampling immediately after the intravenous dosings of etonogestrel was done to study the primary pharmacokinetic parameters, i.e., volume of distribution and clearance, allowing the calculation of the absorption rate and bioavailability of the implant, as a function of time. Results showed that etonogestrel released from Implanon has an absorption rate of approximately 60 micrograms/day after 3 months, which slowly decreases to 30 micrograms/day at the end of 2 years. The bioavailability over this period of time was constant and close to 100%. The clearance remained around 7.5 L/h. With a bioavailability and clearance that remained constant, it may be concluded that there is no accumulation of etonogestrel.
Absorption↗
RETRACTED: The pharmacodynamics and efficacy of Implanon. An overview of the data.
Implanon is a long-acting reversible contraceptive method, consisting of a single rod that is applied subdermally. Ovulation inhibition was determined by serum progesterone (P) levels and ultrasound scanning (USS) of the ovaries. Ovarian function was further assessed by serum estradiol (E2) levels. The effects of Implanon on serum gonadotropin levels (follicle-stimulating hormone [FSH] and luteinizing hormone [LH]) and on cervical mucus were also investigated, by means of Insler scores and sperm penetration tests. The effect of the endometrium was assessed by endometrial biopsies and USS. The Pearl index was calculated over 13 studies performed according to Good Clinical Practice (GCP), including 1716 women using Implanon. Return of ovulation after implant removal was determined by P levels and USS of the ovaries. The contraceptive efficacy of Implanon was high, with zero pregnancies during 53,530 cycles (4103 woman-years), resulting in a Pearl index of 0.0 (95% confidence interval, 0.00-0.09). This was achieved by inhibition of ovulation, which was reflected by suppressed P levels, as the primary mode of action. Ovulation was inhibited, but otherwise ovarian activity was still present (follicle growth, E2 synthesis). The FSH serum concentrations were only slightly lower than preinsertion levels and LH surges were prevented. The viscosity of the cervical mucus was increased. The endometrium was thin but not atrophic; it showed primarily inactive or weak proliferation. Return of ovulation after removal of Implanon was rapid.
Adolescent↗
RETRACTED: Pharmacokinetics of Implanon. An integrated analysis.
The aims of this paper were to present data on the pharmacokinetics, clearance, bioavailability, and in vivo absorption of etonogestrel (ENG); to present the results of a longitudinal analysis of the plasma concentration-time curves of ENG; and to present the results of a cross-sectional analysis on the association of body weight with serum ENG concentrations. Implanon had an absorption rate of almost 60 micrograms/day after 3 months, which slowly decreased to 30 micrograms/day at the end of 2 years. The bioavailability over this period of time was constant and close to 100%. The clearance remained around 7.5 L/h. With a bioavailability and clearance that remained constant, it was concluded that accumulation of ENG does not occur. After Implanon insertion, serum concentrations increased within 8 h to concentrations associated with ovulation inhibition. Maximum mean serum concentrations (Cmax) amounted to 813 pg/mL and the time (tmax) to reach Cmax was 4 days. After reaching Cmax, ENG serum concentrations declined to about 196 pg/mL at the end of the first year, followed by a slow decline to 156 pg/mL at the end of the third year. After removal of Implanon, serum ENG concentrations declined to levels less than the detection limit of the assay (20 pg/mL) within 1 week. Lower body weight was associated with higher serum ENG concentrations.
Absorption↗
RETRACTED: Insertion and removal of Implanon.
Implanon is a single-rod contraceptive implant containing the progestin etonogestrel. Implants require insertion and removal by medical professionals. Detailed and unbiased counseling before insertion is essential, and should include contraceptive efficacy, insertion and removal procedures, and possible adverse events. Insertion and removal times have been measured in six open studies and in seven comparative studies in which Norplant (the six-capsule levonorgestrel implant) was used as the reference product. In comparative studies, the mean time needed for insertion of Implanon was 1.1 min and removal took 2.6 min. Insertion as well as removal of Implanon was four times faster than with Norplant. Complications with insertion and removal are rare in the hands of medical professionals familiar with the techniques.
Adolescent↗
RETRACTED: An integrated analysis of nonmenstrual adverse events with Implanon.
This integrated analysis evaluates nonmenstrual adverse events, blood pressure, and body weight changes during the use of the single-rod etonogestrel-containing contraceptive implant, Implanon; these aspects are compared for Implanon and Norplant, the six-capsule implant containing levonorgestrel. Overall, 47% of Implanon users had drug-related adverse events, whereas in the comparative studies the figure for those using Implanon (61%) was slightly lower than that for Norplant users (69%). In all Implanon studies, 12 of 1716 women (0.7%) were affected by serious adverse events that were considered drug related. In comparative studies three of the 689 Implanon users (0.4%) and one of 689 Norplant users (0.1%) had such experiences. The most frequently reported drug-related adverse events were acne, breast pain, headache and weight gain. The adverse events that most often caused discontinuation of Implanon were weight gain and acne. The development or aggravation of acne was a frequent adverse event (in 18.5% of Implanon and 22.3% of Norplant users in the comparative studies) but individual studies indicated that there were also many subjects whose acne improved during implant use. There were gradual increases in body weight over time but these may be only partly attributable to implant use and partly attributable to normal increases over time.
Acne Vulgaris↗
RETRACTED: An integrated analysis of vaginal bleeding patterns in clinical trials of Implanon.
The vaginal bleeding patterns observed during the use of the single-rod progestin-only implant, Implanon, compared with those seen during the use of the six-capsule implant, Norplant, have been analyzed. The acceptability of these bleeding patterns was also assessed. An integrated analysis of 13 different trials was done, studying reference periods (RP) of 90 days. These trials included totals of 1716 Implanon users and 689 Norplant users. There were statistically significant lower mean values over RP 2-8 the range over RP 2-8 is presented) for Implanon, for the number of bleeding-spotting days (15.9-19.3 vs 19.4-21.6; p = 0.0169), the number of bleeding days (7.5-10.0 vs. 11.7-13.1; p < 0.001), and the number of bleeding-spotting episodes (2.2-2.7 vs. 3.1-3.3; p < 0.0001). The bleeding patterns of Implanon users appeared to be more variable than those observed with Norplant: Implanon users had more amenorrhea, and slightly more infrequent bleeding, frequent bleeding, and prolonged bleeding than Norplant users. The difference was only statistically significant for amenorrhea (17.9%-24.8% with Implanon compared with 2.0%-7.0% for Norplant over RP 2-8). There were no statistically significant differences in the acceptability of the two products as indicated by the discontinuation rates, which were 30.2% and 0.9% in Europe and Southeast Asia, respectively, for Implanon, and 22.5% and 1.4%, respectively, in the two regions, for Norplant. The individual bleeding pattern was not predictable. However, in general, it can be stated that women initially without bleeding or with infrequent bleeding have only a small chance of becoming frequent bleeders, and vice versa. Dysmenorrhea clearly improved during use of both Implanon and Norplant. Neither Implanon nor Norplant caused anemia.
Adolescent↗
RETRACTED: A pilot efficacy study with a single-rod contraceptive implant (Implanon) in 200 Indonesian women treated for < or = 4 years.
In this 4-year open-label, noncomparative, single-center pilot efficacy study, the contraceptive efficacy, safety, bleeding pattern and acceptability of Implanon was studied in 200 sexually active women of proven fertility in Indonesia. All subjects received the single-rod subdermal implant Implanon, which contains 68 mg etonogestrel (3-keto-desogestrel), with an initial release rate of 67 micrograms etonogestrel/day. Contraceptive efficacy was analyzed by calculation of the pregnancy rate, bleeding patterns were determined by the 90-day reference period method, and acceptability by the discontinuation rate. No in-treatment pregnancies were reported during 658.4 women-years of exposure, resulting in a Pearl Index of 0.0 (95% CI 0.0-0.6). The overall bleeding pattern was acceptable, with no discontinuations because of irregular bleeding. Incidence of irregular bleeding was highest during the first two reference periods and decreased thereafter. Amenorrhea was experienced by 7%-12% of subjects during years 1 and 2, by 5%-7% during year 3, and by 2%-5% during year 4, with one discontinuation because of amenorrhea. No clinically significant changes were reported for systolic and diastolic blood pressure, body mass index, and hemoglobin level. Three adverse experiences were related to treatment and resulted in discontinuation (two headaches and one dyspnea). One difficult implant removal was reported. In conclusion, this pilot efficacy study indicates that Implanon provides excellent contraceptive reliability and an acceptable bleeding pattern. Overall safety and acceptability are good, as suggested by the low incidence of adverse experiences and the low discontinuation rate.
Adolescent↗