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Biomedical subjects

P F Van Look

Publications and source records attributed to P F Van Look.

At least 19 recordsLinked to original sources
PubMed2000

Interventions for emergency contraception.

OBJECTIVES: To determine which emergency contraceptive method following unprotected intercourse is the most effective, safe and convenient for use in preventing pregnancy. SEARCH STRATEGY: The search strategy included electronic searches of the Cochrane Controlled Trials Register, Popline, Chinese biomedical databases and HRP emergency contraception database. In addition, references of retrieved papers were searched and researchers in the field and two pharmaceutical companies were contacted. SELECTION CRITERIA: Randomized or quasi-randomized studies including women attending services for emergency contraception following a single act of unprotected intercourse were eligible. DATA COLLECTION AND ANALYSIS: Data on outcomes and trial characteristics were extracted in duplicate by two reviewers. Results were expressed as relative risk using a fixed-effects model with 95 % confidence interval. MAIN RESULTS: Fifteen trials were included in the review. The majority (8/15) of the trials were conducted in China. Most comparisons between different interventions included one or two trials although some trials were appropriately sized with power calculations. Levonorgestrel appears to be more effective than Yuzpe regimen (2 trials, RR: 0.51, 95 % CI: 0.31-0.84) and causes less side-effects (RR: 0.80, 95 % CI: 0.76 to 0.84). Levonorgestrel was less effective than locally manufactured mifepristone in a single, large Chinese study (RR: 2.17, 95 % CI: 1.00 to 4.77). Effectiveness of different doses of mifepristone seem to be similar but the frequency of delay in onset of the subsequent menstrual period increases with increased dose. REVIEWER'S CONCLUSIONS: Levonorgestrel and mifepristone seem to offer the highest efficacy with an acceptable side-effect profile. One disadvantage of mifepristone is that it causes delays in onset of subsequent menses which may induce anxiety. However, this seems to be dose-related and low doses of mifepristone minimise this side-effect without compromising effectiveness. Future studies should compare the effectiveness of mifepristone with levonorgestrel.

Contraceptives, Postcoital↗
PubMed1997

Multicenter study of the Lactational Amenorrhea Method (LAM): I. Efficacy, duration, and implications for clinical application.

A multicenter study of the Lactational Amenorrhea Method (LAM) was carried out to test the acceptability and efficacy of the method. Additionally, the data are used to test new constructs for improvement of method criteria. A protocol was designed at the Institute for Reproductive Health (IRH), Department of Obstetrics and Gynecology, Georgetown University Medical Center, a World Health Organization (WHO) Collaborating Center, and was reviewed and modified in collaboration with the co-sponsors, the World Health Organization and the South to South Cooperation for Reproductive Health, and the principal investigators from each site. Data were gathered prospectively on LAM acceptors at 11 sites. Data were entered and cleaned on-site and further cleaned and analyzed at IRH, using country-level and pooled data to produce descriptive statistics and life tables. The 98+% efficacy of LAM is confirmed in a wide variety of settings. In addition, the results yield insight on the possibility of continued use beyond 6 months. LAM is found to be highly effective as an introductory postpartum method when offered in a variety of cultures, health care settings, socio-economic strata, and industrial and developing country locales. In addition, LAM acceptance complements breastfeeding behaviors without ongoing breastfeeding support services. The parameters studied yield high efficacy and method continuation. Therefore, the basic tenets of the 1995 Bellagio consensus on LAM is reconfirmed and it is recommended that LAM be reconfirmed and it is recommended that LAM be incorporated into hospital, maternity, family planning, maternal and child health, and other primary health care settings.

Adult↗
PubMed1997

Multicenter study of the Lactational Amenorrhea Method (LAM): II. Acceptability, utility, and policy implications.

A multicenter study of the Lactational Amenorrhea Method (LAM) was carried out to determine acceptability, satisfaction, and utilization in 10 different populations, and to confirm the efficacy of the method. Efficacy data are presented in a companion paper. A protocol was designed at the Institute for Reproductive Health (IRH), Department of Obstetrics and Gynecology, Georgetown University Medical Center, and reviewed and modified in collaboration with the co-sponsors, the World Health Organization, the South-to-South Cooperation for Reproductive Health, and the principal investigators from each site. Data were gathered prospectively on LAM users at 11 sites. Data were entered and cleaned on-site, and further cleaned and analyzed at IRH, using country-level and pooled data to produce descriptive statistics. The overall satisfaction with LAM was 83.6%, and continuation with another method of family planning was shown to be 67.6% at 9 months postpartum, in most cases exceeding previous use of contraception prior to use of LAM. Knowledge and understanding of the method at discontinuation were high, ranging from 78.4 to 88.6% for the three criteria. LAM can be used with a high level of satisfaction and success by women in a variety of cultures, health care settings, socio-economic strata, and industrial and developing country settings. The results confirm that LAM is acceptable and ready for widespread use, and should be included in the range of services available in maternal and child health, family planning, and other primary health care settings.

Adult↗
PubMed1996

Effects of two antiprogestins on early pregnancy in the long-tailed macaque (Macaca fascicularis).

The abortifacient effects of mifepristone and HRP 2000 were compared in gravid long-tailed macaques. Thirty-six animals were studied with treatment administered either by the oral (0.5 or 5.0 mg/kg; N = 5 per antiprogestin per dose) or intramuscular (i.m.) routes (0.5 mg/kg; N = 5 per antiprogestin) on gestational days (GD) 23-26; six vehicle controls were included. Blood samples were collected for assay of progesterone (P4) and each of the antiprogestins (pre-treatment, daily GD 23-28, every other day GD 30-40), and animals were monitored sonographically throughout gestation. Results of these studies indicated high rates of abortion with i.m. administration (3/5 mifepristone, 4/5 HRP 2000) and 5.0 mg/kg oral route (4/5, 2/5, respectively), with less effects noted at oral doses of 0.5 mg/kg (2/5, 0/5, respectively). No early abortions were observed in the control groups. Following daily i.m. treatment, peak levels of 8-16 ng/ml mifepristone were detected whereas 6-10 ng/ ml of HRP 2000 were noted (GD 26-27). No serum levels of mifepristone were detected following either of the oral doses whereas serum levels of 2-6 ng/ml HRP 2000 were noted with high dose oral administratation. Results of these studies suggest: (1) both antiprogestins are roughly comparable in terminating early pregnancy although HRP 2000 may be more efficacious when administered i.m. whereas mifepristone may be more effective when administered orally; (2) similar levels of biological activity are seen with the i.m. and high dose oral dosing regimens, with little or no activity with the oral low dose; and (3) infants resulting from surviving pregnancies were not affected by early gestation exposure.

Abortifacient Agents, Steroidal↗
PubMed1995

Clinical uses of antiprogestogens.

Antiprogestogens, which block the action of progesterone at the cellular level through binding to the progesterone receptor, are proving to be one of the most significant developments in endocrinology in recent years. Several hundreds of such compounds have been synthesized, but only a few of them have been evaluated to any significant extent in biological screening models and, to our knowledge, only three compounds, namely mifepristone, lilopristone (ZK 98.734) and onapristone (ZK 98.299) have been given to humans. Most of the clinical research to date has focused on the use of mifepristone given in combination with prostaglandin for termination of early pregnancy, an indication for which the compound is being used routinely in four countries so far, i.e. China, France, the UK and Sweden. The gynaecological and obstetrical applications in which antiprogestogens have been shown to be of value to date include ripening of the pregnant cervix prior to pregnancy termination, sensitization of the uterus to prostaglandins in second-trimester abortion, and induction of labour. Available data suggest that antiprogestogens have no place in the conservative treatment of ectopic pregnancy or in the treatment of premenstrual tension. In fertility regulation, the sequential combination regimen of mifepristone plus prostaglandin as used for inducing abortion has proved to be effective also for menses induction and can be expected to be an efficacious once-a-month contraceptive. Mifepristone alone, without adjuvant prostaglandin, has yielded promising results as an anti-implantation agent and in emergency contraception. Other potential uses include once-a-week contraception, ovulation inhibition (in a sequential regimen with a progestogen), and as a daily mini-pill. Mifepristone, and other antiprogestogens for which biological data have been reported also bind to the cellular receptors for glucocorticoid hormones and, consequently, possess antiglucocorticoid in addition to their antiprogestational activity. Because of this antiglucocorticoid effect, mifepristone has been employed successfully in the palliative treatment of hypercortisolism due to Cushing's syndrome, and its use has been proposed for treating certain forms of depression and of glaucoma, and in wound healing. However, for scientific and practical reasons, it would be preferable if molecules were developed that have only the antiprogestational or the antiglucocorticoid activity rather than both.

Abortion, Induced↗
PubMed1993

Pharmacokinetic study of RU 486 and its metabolites after oral administration of single doses to pregnant and non-pregnant women.

RU 486 and three of its metabolites (RU 42633-monodemethyl, RU 42848-didemethyl, and RU 42698-hydroxymetabolite) were determined by HPLC in plasma from nine non-pregnant and 36 pregnant women. Each non-pregnant subject took an oral dose of RU 486 (25, 100, 400 and 600 mg consecutively) once per menstrual cycle. Six of the nine women also received a dose of 200 mg. The 36 pregnant women were randomized into four groups which were given a single dose of 25, 100, 400 or 600 mg RU 486. Blood samples were taken up to 120 h after dosing. Peak concentrations of RU 486 occurred on most occasions within 2 h. Plasma concentrations at 1 h and at 24 h increased in proportion to log dose. There was a wide variability (up to ten-fold) in the pharmacokinetic parameters within each dose group. Plasma concentrations of RU 42633 were similar to those of RU 486 but concentrations of RU 42848 and RU 42698 were much lower. As with RU 486, the plasma concentrations of the metabolites were maintained at high levels for up to 48-72 h after dosing. The findings were consistent with a rapid metabolism of RU 486 to RU 42633; removal of the second methyl group leading to RU 42698 occurred much more slowly and to a much less extent than removal of the first. There appeared to be no significant differences between the non-pregnant and pregnant women in either the plasma concentrations or pharmacokinetic parameters of RU 486 and its metabolites.

Administration, Oral↗
PubMed1993

Tamoxifen as an antifertility agent in the long-tailed macaque (Macaca fascicularis).

The potential use of tamoxifen, a nonsteroidal antiestrogen, as an antifertility agent was studied in the long-tailed macaque (Macaca fascicularis). Twenty-six cycling females were bred, then treated with a single oral dose of tamoxifen (5 mg/kg) (N = 13) or vehicle (N = 13) on day 4 post-ovulation. Serum progesterone (P4) and tamoxifen concentrations were evaluated on post-ovulation days 4, 8, 12, 16, and 18. No effects of treatment were observed on P4 concentrations or on the fertility rate--pregnancy was achieved in 4/13 controls (31%) and 6/13 treated females (46%). Analysis for serum tamoxifen concentrations in samples collected during the fertility and a supplemental pharmacokinetic study (N = 3; single oral dose of 10 mg/kg; urine and serum evaluated) failed to reveal any detectable tamoxifen levels. It was concluded that (1) absorption of tamoxifen may be negligible under the described treatment regimens or (2) tamoxifen metabolism/clearance occurs at a rapid rate.

Administration, Oral↗
PubMed1993

Emergency contraception.

The term 'emergency contraception', as employed in this paper, refers to methods that are used as emergency procedures to prevent pregnancy following unprotected intercourse. Alternative, less appropriate, terms are postcoital and 'morning-after' contraception. References to postcoital preparations can be found as far back as 1500 BC in Egyptian papyri, but it was not until fairly recently that contraceptive research has been able to at least partially fulfill that need. The development of hormonal methods of emergency contraception goes back to the 1960s when the first human trials of postcoitally administered high-dose oestrogens were undertaken. Combined oestrogen- progestogen combination therapy (the so-called Yuzpe regimen) was introduced in the early 1970s, while the postcoital insertion of an intrauterine contraceptive device (IUD) for emergency contraception was first reported in 1976. Other compounds that have been tested more recently include levonorgestrel, the antiprogestogen mifepristone, and danazol. Although there is some debate about the magnitude of the protective effect, few people question the important role that emergency contraception can play in preventing unwanted pregnancy and hence maternal mortality and morbidity resulting from unsafe abortion. Given that the most often used methods of emergency contraception, namely the Yuzpe regimen and postcoital insertion of an IUD, rely on technology that has been available for some 30 years, family planning programmes that claim to be concerned with improving women's reproductive health, cannot really be excused if they do not provide emergency contraception as part of their routine services.

Contraception↗
PubMed1993

Population growth.

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Contraceptive Agents↗
PubMed1991

A multicenter clinical study on two types of levonorgestrel tablets administered for postcoital contraception.

Contraceptive efficacy, cycle control and side effects of two types of 0.75 mg levonorgestrel tablets taken postcoitally during the periovulatory period of one cycle were studied in a multicenter trial involving 361 women. No significant differences were found between the two types of levonorgestrel pills in terms of contraceptive efficacy, cycle control and side effects. The failure rate observed (1.4% per treated cycle) was similar to that reported for other hormonal approaches to emergency postcoital contraception. Intermenstrual bleeding or spotting occurred in 11.5% of the cycles and anovulation as assessed from BBT charts in 14.4% of cycles. One or more side effects were reported by 22.2% of subjects. The relatively frequent occurrence of cycle disturbances and subjective side effects make it unlikely that the repeated postcoital use of levonorgestrel would be an acceptable routine method of contraception for most women.

Adult↗
PubMed1990

Comparative cross-over pharmacokinetic study on two types of postcoital contraceptive tablets containing levonorgestrel.

A pharmaceutical and pharmacokinetic study was carried out on levonorgestrel tablets from two different sources (Hungarian- and Chinese-made). Both preparations contained 0.75 mg levonorgestrel and had been shown to have similar contraceptive efficacy and side effects when used for postcoital contraception. Absorption and bioavailability of the Hungarian-made tablets were greater as evidenced by higher serum concentrations of levonorgestrel, a greater area under the concentration-time curve during the first 24 hours, and a more marked suppressive effect on SHBG levels. These differences most probably reflect differences in their pharmaceutical formulation, in particular the extent of tablet dissolution and the degree of micronisation of levonorgestrel.

Absorption↗