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Biomedical subjects

M Pavez

Publications and source records attributed to M Pavez.

At least 37 records · Page 2Linked to original sources
PubMed1988

Clearance of levonorgestrel from the circulation following removal of NORPLANT subdermal implants.

The disappearance of levonorgestrel from plasma after the removal of NORPLANT subdermal implants was studied in 12 women who had been treated from 5.5 to 78 months. The existence of one or two half-lives for the rate of disappearance was assessed. The influence of body weight, body fat and length of treatment upon levonorgestrel clearance was studied through stepwise regression analysis. It was found that the levonorgestrel decay rate after implant removal can be entirely accounted assuming one half-life of 42 +/- 16 h (mean +/- SD; range 13 to 62 h). Stepwise regression analysis showed that levonorgestrel half-life is positively correlated with body weight and not significantly correlated with the length of treatment or body fat. It is concluded that, after long-term administration of levonorgestrel via subdermal implants, the major part of the steroid is cleared from plasma within 96 h and that only trace amounts are detected in the following days.

Adult↗
PubMed1987

Two years of intrauterine contraception with levonorgestrel and with copper: a randomized comparison of the TCu 380Ag and levonorgestrel 20 mcg/day devices.

IUDs releasing 20 mcg/day of levonorgestrel (LNg20) were in randomized trial together with the Copper T, model TCu 380Ag, in seven centers involving 2244 women. Two-year (25 months) gross cumulative pregnancy rates were 0.2 +/- 0.2 and 0.9 +/- 0.3 for the levonorgestrel and copper releasing devices, respectively (P greater than 0.05). There were no ectopic pregnancies in more than 1600 woman-years of use of each device. Removal rates for bleeding and/or pain or for medical reasons other than menstrual problems did not differ significantly between devices. Oligomenorrhea or amenorrhea prompted 10.7 per hundred (gross rate, 8.4 net rate) women using the LNg 20 IUD to request removal in the two-year period, significantly above the 0.2 per hundred rate among women with the Copper IUD (P less than 0.001). At the end of two years an estimated 59.4 per 100 women were continuing use of the LNg 20 IUD, and 67.5 per 100 (P less than 0.001) with the TCu 380Ag. This difference is almost wholly ascribable to a marked reduction in bleeding episodes and days among women using the LNg 20 device with concomitant removal of device. Hemoglobin rose an average of 0.5 g/dl (P less than 0.001) for this group whereas women using the TCu 380Ag experienced a decline of 0.2 g/dl compared with baseline values (P less than 0.001).

Adolescent↗
PubMed1987

Long-term follow-up of women treated with Norplant implants.

This report describes the long-term follow-up of 376 women who received NORPLANT implants in the period October 1974 through May 1979. One-hundred-and-ten subjects received replacement implants after variable lengths of use of the first set. The average levonorgestrel plasma levels declined steadily through eight years of use of NORPLANT capsules (r = -.937). Values were 0.35 ng/ml, 0.29 ng/ml and 0.22 ng/ml at treatment years 1, 5 and 8, respectively. Levonorgestrel plasma levels after replacement with a second set of implants were similar to those observed after the first insertion, either when placed in the same site as the first set or in a different area. Nineteen pregnancies occurred during 18,530 woman-months of use of the first set of implants, eleven of them during years 6 through 8 of treatment. The Pearl Index for the first 5 years of NORPLANT implants use was 0.63. No pregnancy has occurred in 4194 woman-months observed during treatment with a second set of capsules. Fifty-six women (14.9%) out of 376 acceptors of the first implant and 10 (9.1%) out of 110 acceptors of the replacement implants were terminated for other medical reasons, mainly bleeding problems and side effects commonly associated with hormonal contraception. Two women died while using NORPLANT implants, one of a cardiac arrest after surgery for a gallbladder disease and one because of endocranial hypertension originating from the rupture of an aneurism of the median cerebral artery. The bleeding pattern observed in the three months after NORPLANT capsules replacement was similar to that observed in the 90 days before replacement and different from that experienced by the same women in the first 90 days of implant use. This finding can be interpreted as an indicator of adaptive changes experienced by the target organs during long-term continuous administration of levonorgestrel. The prompt recovery of fertility after removal of NORPLANT implants suggests that these changes are reversible.

Adult↗
PubMed1987

Recovery of fertility and outcome of planned pregnancies after the removal of Norplant subdermal implants or Copper-T IUDs.

The recovery of fertility after discontinuation of NORPLANT implant use was assessed in ninety women who stated a desire for a new child at the time of removal. Three subjects were lost to follow-up after removal. The cumulative probability of conception in the remaining 87 women was 25, 49, 73 and 86 percent at one, three, six and twelve months after removal, respectively. Nine observations were censored either because of the use of a contraceptive method soon after removal of the implants (n = 7) or separation (n = 2). All other cases were pregnant at the end of two years with exception of three subjects where a male factor for infertility was present. There was no significant correlation between the length of NORPLANT use and the length of the interval from removal to conception. A significantly higher frequency of intervals longer than 6 months was observed among women older than 30 years as compared to younger women. Pathology during pregnancy was cholestasia (n = 5), hypertension (n = 1) and gestational diabetes (n = 1). The outcome was term delivery in 59 cases, premature delivery in 4 cases, and spontaneous abortion in 7 cases. One woman is still pregnant and the outcome is unknown in 4 cases. One premature infant died. A contemporary control group of Copper T users enrolled under the same criteria as NORPLANT implant users provided 44 women who had the device removed to become pregnant. The cumulative probability of pregnancy was 27, 69, 84 and 89 at one, three, six and twelve months and all were pregnant by the end of the second year. Six censored observations occurred because of the use of another contraceptive method after removal (n = 3) or loss to follow-up (n = 3). The outcome of pregnancy was term delivery in 23 cases and abortion in 7 cases. Recovery of fertility occurred at a normal rate after NORPLANT implant removal and the incidence of problems detected in the ensuing pregnancy were within the expected range for Chilean women.

Age Factors↗
PubMed1986

Recovery of fertility after use of the levonorgestrel 20 mcg/d or Copper T 380 Ag intrauterine device.

Following use of either the Levonorgestrel 20 mcg/day or the TCu 380 Ag IUD in a randomized comparative study, 110 women stopped contracepting to have planned pregnancies. Pregnancy rates and recovery of fertility have been assessed. Age at acceptance, duration of use, parity and intervals between last pregnancy and IUD insertion or removal were similar for both groups. Life table pregnancy rates at one year were higher than 90 per cent for both device groups; but because some women quickly changed their minds or had been at risk of pregnancy only a short time before the analysis date, only 60.9 percent had actually become pregnant. Median time to planned pregnancy was 3 months for the TCu 380 Ag group and 4 months for the Levonorgestrel 20 group. Neither duration of use nor age at insertion or age at termination affected the pregnancy rates significantly.

Adult↗
PubMed1986

Bleeding pattern, outcome of accidental pregnancies and levonorgestrel plasma levels associated with method failure in Norplant implants users.

The aim of this study was to characterize the bleeding pattern, the outcome of pregnancies and the levonorgestrel plasma levels associated with method failures in Norplant implants users. Nineteen pregnancies are reported in 458 woman and 21,589 woman-months observed during the first eight years of Norplant use. Pregnancy rates increased slightly during the first six years of use, attaining a Pearl Index above three thereafter. All women who became pregnant had experienced a regular bleeding pattern in the six months preceding conception. Levonorgestrel plasma levels observed at different intervals before conception and during the conceptional cycle were similar to those observed in non-pregnant women at comparable intervals after Norplant insertion. The nineteen pregnancies ended in thirteen term deliveries, one premature delivery, three abortions and two ectopic pregnancies. No abnormalities were found in the infants. The two ectopic pregnancies are the only ones reported for Norplant users in The Population Council studies. The overall incidence is less than 0.8 per 1000 woman-years.

Abortion, Spontaneous↗
PubMed1985

Clinical chemistry in women treated with six levonorgestrel covered rods or with a copper IUD.

A group of women treated with six levonorgestrel covered rods participated in a study on general chemistry and blood levels of selected hormones at treatment months 20 and 65. A comparable group of Copper T users served as control. Parameters analyzed were the SMA 12 chemistry profile, estradiol, testosterone, cortisol, T3, T4 and TSH. Samples from treated and control subjects were drawn within the same calendar period and were run simultaneously for the assay of each parameter. The values observed were within the normal limits. Significantly higher values of total protein and albumin and lower levels of estradiol and testosterone were found among implant users when compared to the control group. The results suggests little or no metabolic changes in users of six levonorgestrel covered rods which release a daily dose of approximately 105 micrograms.

Adolescent↗
PubMed1985

Plasma levonorgestrel and progesterone levels in women treated with silastic covered rods containing levonorgestrel.

Levonorgestrel and progesterone plasma levels were measured in women bearing levonorgestrel subdermal implants. Two groups using four or six levonorgestrel covered rods and one group of non-hormonal contraceptors were compared. Blood samples were drawn twice a week for six consecutive weeks at different intervals after treatment administration. The mean levonorgestrel levels (mean +/- S.D.) observed in the four rods group was .49 +/- .13 ng/ml in the first year and decreased to .34 +/- .06 in the fifth year of treatment. The mean values observed in the six rods group were .70 +/- .15 ng/ml in the second year and .43 +/- .11 in the sixth year. The levonorgestrel plasma levels were slightly above those found with Norplantr implants in the four rods group and well above it in the six rod group. The highest plasma progesterone value found in each sampling period was above 9 nmol/l in 7 (14%) out of 50 subjects in the four rods group, in 2 (4.3%) out of 47 subjects in the six rods group and in all the 49 control women. In 4 out of the 7 subjects from the 4 rods group and in the two subjects from the 6 rods group, the highest progesterone value was preceded and followed by values lower than 6 nmol/l. It was concluded that the progesterone levels were seldom compatible with the occurrence of ovulation in women treated with four or six levonorgestrel covered rods which release an estimated daily dose of 70 and 105 micrograms, respectively.

Adolescent↗
PubMed1984

Intrauterine contraception with copper and with levonorgestrel: a randomized study of the TCu 380Ag and levonorgestrel 20 mcg/day devices.

First year results of a randomized study of 1509 users of the Copper T380Ag with a silver core or of an IUD releasing 20 mcg day of levonorgestrel are reported. The cumulative gross pregnancy rate for each device was 0.3 per 100 at one year, with more than 490 women having one year of use with each device. The levonorgestrel-releasing device was associated with significantly fewer bleeding days and significantly increased hemoglobin levels when compared with pre-admission values or the one year values observed among users of the TCu380Ag. Terminations attributable to amenorrhea were significantly more frequent among users of the levonorgestrel-releasing device. The TCu 380Ag was associated with increased frequency and severity of dysmenorrhea compared with pre-admission levels or with the steroid-releasing device. Hemoglobin levels were somewhat reduced among users of the TCu 380Ag device. Terminations attributable to pain were, however, not significantly different by device. Continuation rates at the end of the first year were not significantly different by device.

Adolescent↗
PubMed1983

Clinical chemistry in women treated with levonorgestrel implants (Norplant) or a TCu 200 IUD.

Two groups of implant users and two groups of IUD users participated in the study at different times. In the first groups, fractionation of lipoproteins was performed on serum samples from 28 subjects who had used the implants for 37 months and from 26 subjects who had used the Copper TCu 200 for 30 months. Users of the implants had significantly lower levels of total cholesterol, triglycerides and LDL-cholesterol than users of the IUDs. HDL-cholesterol levels were not different between the groups. In the other groups of women, general chemistries and selected hormone assays were carried out on samples from 30 subjects who had used implants for 51 months and from 24 subjects who had used the TCu 200 IUDs for 43 months. The parameters studied were the SM-12 chemistry group profile, estradiol, cortisol, testosterone, triiodothyronine, thyroxine and thyroid stimulating hormone. In the implant group, mean serum glucose levels were statistically significantly elevated and inorganic phosphorus levels were significantly reduced as compared to the IUD group. In both cases all individual measurements were within the normal range for the population. Testosterone and triiodothyronine levels in the implant group were significantly lower than in the IUD group, but no individual values were outside the normal range for the population. Mean values for all other parameters were not significantly different between the groups.

Adult↗
PubMed1982

A five-year clinical trial of levonorgestrel silastic implants (Norplant TM).

Silastic implants containing the progestin, levonorgestrel, were tested as a long-term contraceptive system in 101 women. During five full years of use, no pregnancies occurred. The 5-year continuation rate was 54%. Menstrual irregularities were the most frequent reason for termination of use but only during the first year. More than half of the terminations for this reason were in the first year. Some of the subjects elected to continue use of the implants beyond 5 years, allowing release rate data to be obtained through 6 years. From the second through the sixth year of use, the implants delivered a constant 30 micrograms per day of levonorgestrel to the subjects, and even after six years 57% of the original steroid content remained in the capsules. Return of fertility following removal was essentially immediate and not related to time of use. Medical reasons for removal were infrequent and no pattern was discernible.

Adult↗
PubMed1982

Plasma progesterone levels during long-term treatment with levonorgestrel silastic implants.

Plasma progesterone levels were measured in 113 women using a subdermal implant containing 200 mg levonorgestrel (NORPLANT) in an attempt to assess the roles of anovulation and inadequate luteal function in the contraceptive action of this method. Twenty-two women using an IUD (Copper T 200) served as a control group. Blood samples were taken twice a week for 6 consecutive weeks. This was done one to four times in each subject during the first 7 years after insertion of NORPLANT. Plasma progesterone was measured by a specific RIA and criteria based upon normal values in this laboratory were used to define each set of samples as ovulatory, uncertain or anovulatory. The rate of anovulation varied between 25 and 80% throughout the 7 years. The highest rate was observed during the first year of treatment of treatment. The rate of anovulation was significantly correlated with the plasma levels of levonorgestrel. Varying degrees of inadequate corpus luteum function were detected among NORPLANT users. All sets of samples in the control group were ovulatory and compatible with normal luteal function. These results clearly show that continuous administration of levonorgestrel by means of NORPLANT interferes with ovulation and/or luteal function in a significant proportion of cycles throughout the first 7 years of use.

Adult↗
PubMed1981

A multicenter study of levonorgestrel-estradiol contraceptive vaginal rings. II-Subjective and objective measures of effects. An international comparative trial.

Comparative clinical trials of 2 sizes of contraceptive vaginal rings and of an oral contraceptive were undertaken at 8 investigational sites (9 clinics). More than 500 women enrolled on each of the 3 study regimens. Side effects of the rings and of Nordette, the oral contraceptive, were evaluated by noting spontaneous complaints, by recording medications taken and by physical examination. Inquiries about changes in the frequency of specific conditions were made at the end of the subjects participation in the first year of the study. The incidence of spontaneous complaints was similar among users of the 2 different-sized rings and of the pill.

Adolescent↗
PubMed1981

A multicenter study of levonorgestrel-estradiol contraceptive vaginal rings. III-Menstrual patterns. An international comparative trial.

Menstrual events among users of contraceptive vaginal rings (CVRs), releasing levonorgestrel and estradiol, were studied in comparison with a combined oral contraceptive, Nordette, in multicentered trials. CVRs were made with outside diameters of 50 and 58 mm and released about 250 micrograms and 290 microgram of levonorgestrel and 150 microgram and 180 microgram of estradiol per day, respectively. The CVRs were used continuously for 3 weeks and then removed for 1 week. Both the CVRs and Nordette were perceived to reduce menstrual flow and days of menstrual bleeding. Twenty to 25% of CVR users perceived increased intermenstrual bleeding or spotting. Diaries indicate, however, that on average, CVR users experienced about 1 day per month of bleeding or spotting with the ring in place. CVRs and Nordette produced approximately the same total number of bleeding and spotting days during 6 cycles of use, 27-29, but the small (50-mm OD) ring was associated with somewhat more spotting. This ring was also associated with somewhat more prolonged bleeding and spotting runs and with more prolonged nonbleeding intervals than reported by users of the larger (58-mm OD) ring or of Nordette. Differences among regimens, however, tended to be small even when statistically significant. Evidence from menstrual diaries indicates that these CVRs, and in particular 58-mm ring, provide control over the menstrual cycle comparable to the Nordette.

Adolescent↗
PubMed1980

Ectopic pregnancies associated with low dose progestagen-releasing IUDs.

Dimethyl-polysiloxane capsules containing pure progestagens were attached to Tatum's T IUDs and tested in 594 fertile women for contraceptive performance. The control group was represented by 71 women who received identical devices containing barium sulphate instead of steroid and 100 women who received a Copper T-200. The progestagens and the doses tested were megestrol acetate (4.8, 19.2, 26 and 32 micrograms/day; levonorgestrel (2.1, 3.4 and 8.5 micrograms/day); norethindrone (18 micrograms/day); R2323 (28.6 and 45 micrograms/day); and norgestrienone (26 micrograms/day). Twelve pregnancies were diagnosed during 5201 woman-months of exposure accumulated within the first year of use among users of the steroid-bearing IUDs. Five of these were ectopic gestations. Ten pregnancies, all uterine, were detected during 1701 woman-months of exposure in the control group. Intrauterine delivery of progestagens by means of a carrier IUD is effective in decreasing the pregnancy rate but it might effect postovulatory events in a way which increases the rate of tubal implantation. Because of this property, progestagen-releasing IUDs should be limited to doses that assure maximal effectiveness to avoid increasing the risk of ectopic pregnancy.

Adolescent↗
PubMed1979

A three-year clinical trial with levonorgestrel silastic implants.

Silastic implants containing the progestin, levonorgestrel, were tested as long-term contraceptives in 101 women. After three full years of exposure and 2,998 woman-months of use, no pregnancies had occurred. The continuation rates were 87% at 12 months, 79% at 24 months and 66% at 36 months. The most important side effect was excessive or irregular bleeding during the first year. No treatment was offered for this side effect other than vitamins and iron or change of method, with the exception of 3 cases where ethinyl estradiol was used one time for 2 weeks each. Bleeding disturbances led 8 patients to ask for removal of implants. Other side effects were headache, acne and lower abdominal pain. Blood and urine analysis tested 17 different parameters and all but plasma cortisol remained within normal limits throughout the study. A general tendency toward lowered cortisol values was observed and two subjects had more than one value below the normal limit for the population during the study. Glucose tolerance tests during the second year were abnormal in two women with familial diabetes but they returned to normal values spontaneously at the next test. It is concluded that levonorgestrel implants offer effective protection against pregnancy during the first three years of continuous use. Their acceptability and few side effects justify larger trials, especially if treatment of bleeding irregularities is introduced.

Abdomen↗