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Dive into the research topics where Margarita Pavez is active.

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Featured researches published by Margarita Pavez.


Contraception | 1991

PROLONGED INTRAUTERINE CONTRACEPTION: A SEVEN-YEAR RANDOMIZED STUDY OF THE LEVONORGESTREL 20 mcg/DAY (LNg 20) AND THE COPPER T380 Ag IUDS

Irving Sivin; Janet Stern; Elsimar M. Coutinho; Carlos E.R. Mattos; Sayed El Mahgoub; Soledad Diaz; Margarita Pavez; Francisco Alvarez; Vivian Brache; Francisco Thevenin; Juan Diaz; Anibal Faundes; Margarita Díaz; Terence McCarthy; Daniel R. Mishell; Donna Shoupe

A levonorgestrel-releasing IUD and the Copper T 380Ag IUD were in randomized comparison for seven years in five clinics. In two other clinics the randomized study was truncated at five years, but use of the Copper T continued. No pregnancies occurred to users of either device in years 6 and 7. Cumulative pregnancy rates were 1.1 per 100 at seven years for the steroid-releasing and 1.4 per 100 for the copper-releasing IUDs. Cumulative rates of PID did not differ between devices. Infection rates appeared to be lowest during the sixth and seventh years of the study. Termination attributable to amenorrhea was the principal contributor to differences in cumulative continuation rates between devices. At the five clinics that carried the comparative study to seven years, cumulative continuation rates were 24.9 per 100 for LNg20 IUD users and 29.4 per 100 for TCu 380Ag users. Women who used either method for periods of five to seven years experienced, on average, marked to mild increases in hemoglobin as compared with levels at admission. The Copper T380 family and the LNg20 IUDs represent the most effective reversible contraceptive methods yet studied in long-term randomized trials.


Contraception | 1990

Long-term contraception with the levonorgestrel 20 mcg/day (LNg 20) and the Copper T 380Ag intrauterine devices: A five-year randomized study

Irving Sivin; Sayed El Mahgoub; Terence McCarthy; Daniel R. Mishell; Donna Shoupe; Francisco Alvarez; Vivian Brache; Elvira Jimenez; Juan Diaz; Anibal Faundes; Margarita Díaz; Elsimar M. Coutinho; Carlos E.R. Mattos; Soledad Diaz; Margarita Pavez; Janet Stern

An intrauterine device, releasing approximately 20 micrograms/day of levonorgestrel (LNg 20), used by 1124 women, was studied in a randomized trial of five years duration in comparison with the Copper T, model TCu 380Agm in 1121 women. At five years, the gross cumulative pregnancy rate of 1.1 +/- 0.5 per 100 among users of the LNg 20 devices was not significantly different from the rate of 1.4 +/- 0.4 per 100 experienced by users of the Copper T 380Ag. The steroid-releasing IUD had significantly higher termination rates for expulsion and amenorrhea, a significantly lower termination rate for other menstrual problems and pain, and a lower continuation rate. The five-year continuation rate among women using the TCu 380Ag was 40.6 per 100 as compared with that of 33.0 per 100 among women randomized to the LNg 20 device (P less than .001). Terminations attributed to amenorrhea with the LNg device primarily account for differences in continuation. These two intrauterine devices are the most effective long-term, reversible IUDs yet reported in the literature. No other contraceptive methods have exhibited such low long-term pregnancy rates in randomized comparative trials.


Contraception | 1982

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

Soledad Diaz; Margarita Pavez; P. Miranda; Dale N. Robertson; Irving Sivin; H.B. Croxatto

Abstract 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.


Contraception | 1990

Clinical assessment of treatments for prolonged bleeding in users of norplantR implants

Soledad Dĺaz; Horacio B. Croxatto; Margarita Pavez; Hedia Belhadj; Janet Stern; Irving Sivin

The effectiveness of three drugs in controlling prolonged bleeding in the first year of NORPLANT implants use was tested. The drugs were levonorgestrel (L-Ng, 0.03 mg twice a day for 20 days), ethinylestradiol (EE, 0.05 mg per day for 20 days) and ibuprofen (Ib, 800 mg three times a day for 5 days) and were given orally. A control group received a placebo (PL, one pill of lactose for 20 days). Treatment should start each time a woman experienced eight consecutive days of bleeding or spotting. The 183 volunteers were not aware of the drug administered. A daily record of bleeding and spotting and of treatment intake was maintained. One-hundred-forty women completed the study period; 60 never used the prescribed treatment. Women treated with the three test drugs had significantly fewer bleeding and spotting days during the treated month and also throughout the study year than women using the placebo. The mean number of bleeding plus spotting days per actually treated subject in the first year was 77, 94, 101 and 129 days for the EE, Ib, L-Ng and PL groups, respectively. The administration of EE might help in the management of prolonged bleeding during the first year of NORPLANT implants use.


American Journal of Obstetrics and Gynecology | 1992

Rates and outcomes of planned pregnancy after use of norplant capsules, norplant II rods, or levonorgestrel-releasing or copper TCu 380Ag intrauterine contraceptive devices

Irving Sivin; Janet Stern; Soledad Diaz; Margarita Pavez; Francisco Alvarez; Vivian Brache; Daniel R. Mishell; Maria Lacarra; Terence McCarthy; Pentti Holma; Philip D. Darney; Cynthia Klaisle; Sven-Eric Olsson; Viveca Odlind

OBJECTIVES The objectives were to measure rates of planned pregnancy and factors affecting these rates after use of very-long-acting contraceptive methods (Norplant or Norplant II implants, a levonorgestrel-releasing intrauterine contraceptive device, or the copper T (model TCu 380Ag) intrauterine contraceptive device. STUDY DESIGN The design was a concurrent, multicenter prospective study of 372 women who stopped contraception for planned pregnancy. Analysis was by life-table, log-rank, and standard chi 2 methods. RESULTS Pregnancy rates 12 and 24 months after cessation of contraceptive use were 82 and 89 per 100, respectively. Age at removal and family planning intentions at initiation of contraception were both significantly correlated with pregnancy rates (p less than 0.05), but former contraceptive regimen and duration of contraceptive use were not. Pregnancy outcomes did not deviate from normal limits and did not differ by contraceptive formerly used. CONCLUSION Contraceptive implants releasing 30 micrograms/day of levonorgestrel or intrauterine contraceptive devices releasing 20 micrograms/day of levonorgestrel or having copper surface areas of 380 mm2 are associated with normal fertility after use for women seeking pregnancy at termination. Durations of use do not affect pregnancy rates.


Contraception | 1984

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

Irving Sivin; Francisco Alvarez; Juan Diaz; Soledad Diaz; Sayed El Mahgoub; Elsimar M. Coutinho; Vivian Brache; Margarita Díaz; Anibal Faundes; Margarita Pavez; Carlos E.R. Mattos; Janet Stern

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.


Contraception | 1986

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

Hedia Belhadj; Irving Sivin; Soledad Diaz; Margarita Pavez; Ana-Sofia Tejada; Vivian Brache; Francisco Alvarez; Donna Shoupe; Harlene Breaux; Daniel R. Mishell; Terry McCarthy; Veronica Yo

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.


Contraception | 1997

Clinical performance of a new two-rod levonorgestrel contraceptive implant : A three-year randomized study with Norplant® implants as controls

Irving Sivin; Osborn Viegas; Italo Campodonico; Soledad Diaz; Margarita Pavez; Livia Wan; Suporn Koetsawang; Orawan Kiriwat; Manee Piya Anant; Pentti Holma; Kamal el din Abdalla; Janet Stern

In a randomized three-year clinical trial at seven clinics, the performance of levonorgestrel rod (LNG ROD) implants used by 600 women was compared with that of soft tubing NORPLANT implants used by 598 women. No pregnancies occurred in either group of women and, accordingly, body weight did not affect the efficacy of either type of implant. There were neither statistically significant nor important differences in termination rates for any reason over the three years. Complaint and illness rates during use of either of the two implant types were statistically indistinguishable and were attributable to the same set of conditions. Seventy-one per 100 of the women using each implant regimen continued to the three-year point, for an average annual continuation rate of 89 per 100. Removals of LNG ROD implants were accomplished in about half the time required for removal of Norplant capsule implants (p < 0.001).


Contraception | 1987

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

Irving Sivin; Janet Stern; Juan Diaz; Margarita Díaz; Anibal Faundes; Sayed El Mahgoub; Soledad Diaz; Margarita Pavez; Elsimar M. Coutinho; Carlos E.R. Mattos; Terry McCarthy; Daniel R. Mishell; Donna Shoupe; Francisco Alvarez; Vivian Brache; Elvira Jimenez

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).


Contraception | 1983

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

H.B. Croxatto; S. Díaz; Dale N. Robertson; Margarita Pavez

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.

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Francisco Alvarez

State University of Campinas

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Daniel R. Mishell

University of Southern California

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S. Díaz

Pontifical Catholic University of Chile

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Anibal Faundes

State University of Campinas

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