Attitudes towards contraceptive implants and injectables among present and former users in Singapore

In a comparison of present and past users of contraceptive implants (Norplant) or injectables (DMPA) and discontinuers of Norplant or DMPA, information concerning the women's knowledge and perception of, and attitude to, implants and injectable contraceptives, was studied. The long duration of action (5 years) of implants was perceived positively by all groups as compared to the shorter 3-month duration of injectables, though this was seen as an advantage over the pill. It appears that the Norplant system has potential for wider use in Singapore in the future.     

The effect of contraceptive implants on the behavior of female Rodrigues fruit bats,Pteropus rodricensis

This study investigated the effects of a melengestrol acetate contraceptive implant on the behavior of captive Rodrigues fruit bats (Pteropus rodricensis). Eighteen female bats (nine controls and nine implanted animals) were studied over three 4 week periods: prior to implantation, immediately postimplantation, and 6 months postimplantation. The only significant differences found 6 months postimplantation were that time spent hanging alert decreased in both groups and, concurrently, amount of time spent engaged in other activities, most noticeably social interactions, increased. In connection with this, the number of nearest neighbors increased. However, these changes were seen in all bats and were also associated with the increasing size of the resident colony. There were no significant differences between the two groups of bats in the number of nearest neighbors or sexual partners over the course of the study. The physical effects of the contraceptive implants, increased weight gain and retarded hair regrowth above the incision site, were very clearly shown. There was a 22% rate of rejection/loss of the implants. None of the implanted bats produced offspring postimplantation. This study has shown that melengestrol acetate implants are an effective way to limit reproduction in female Rodrigues fruit bats, at least in the short term, and have no effect on the behavior of this highly social species. © 1996 Wiley-Liss. Inc.     

Restoration of reproductive potential after expiration or removal of melengestrol acetate contraceptive implants in Tigers (Panthera tigris)

The need for contraception in the successful management of captive wild animals is becoming increasingly apparent. Because concerns exist regarding the reversibility of the contraceptive implant melengestrol acetate (MGA), reproductive data for 94 female Amur (Panthera tigris altaica) and Sumatran tigers (Panthera tigris sumatrae) were analyzed using survival analyses to evaluate return to reproductive status after implant removal or assumed expiration. Females placed in potential breeding situations after MGA implants were surgically removed showed a 62% return to reproduction by 5.25 years, whereas females with implants that were assumed to have expired showed only a 30% return to reproduction by 6 years. Implanted females did not reproduce as successfully as non‐implanted control females, which showed an 85% probability of reproducing after placement in a new breeding situation by 2.66 years. Parturition increased the probability of reproducing in non‐implanted females, but not in implanted females. Litter size, stillbirths, and offspring survival were not significantly different between non‐implanted, implant‐removed and implant‐expired female tigers. Ten female tigers reproduced both before and after implant placement, and the differences in litter size, stillbirths, and offspring survival were not significant, nor were they significantly different from non‐implanted females. Prior parturition, age when implant was removed, and duration of implantation did not affect the probability of reproducing for females after implant removal. These results show substantial reversibility of MGA implants, leading to 62% successful reproduction after implant removal. The reasons for lower successful reproduction in animals previously treated with the contraceptive compared to non‐implanted females are not known, but a greater delay in reversibility was seen when implants were left in place and only presumed expired. Zoo Biol 26:275–288, 2007. © 2007 Wiley‐Liss, Inc.     

Progestin-only contraceptive rings

Several progestin-only long acting contraceptives are currently available in the form of implants or injectables. Vaginal rings are another contraceptive option in the final stages of development. These steroid-containing polymer rings are placed in the vagina, providing relatively constant drug release, thus allowing for lower effective doses. Vaginal rings have the advantage of being user-controlled and non-provider dependent, and their use is non-coital related. The first clinical study with medroxyprogesterone acetate vaginal rings was published in 1970. Since then numerous clinical trials testing different steroids and doses have followed. A large Phase III multicenter clinical trial with a levonorgestrel ring, releasing 20 microg/day, was coordinated and sponsored by WHO. The cumulative one-year pregnancy rate was 4. 5%. The principal reasons for discontinuation were menstrual disturbances (17.2%), followed by frequent expulsion of the ring (7. 1%), and vaginal symptoms (6.0%). The finding of erythematous lesions in the vagina in some women has led to the development of a more flexible device. Collaboration with industry should facilitate the manufacture of a redesigned levonorgestrel ring with a higher release rate. The Population Council is also developing a vaginal ring containing Nestorone for 6 months of continuous use. Ovulation inhibition was achieved in over 97% of the segments studied, with rings releasing either 50, 75, or 100 microg/day. No pregnancies occurred in women using the low-dose ring, while one pregnancy each occurred in the intermediate- and high-dose ring groups for a 6-month cumulative pregnancy rate of 0.0, 1.9, and 2.1%. Bleeding irregularities were common. Nestorone is orally inactive; therefore this ring is also excellent for use in lactating women.     

Norethisterone contraceptive microspheres

Two formulations of polylactic and polyglycolic acid microcapsules containing 75 and 100 mg of NET respectively were studied for a 90-day period of anticipated contraceptive effect in two groups of five women. A 200 mg dose of NET preparation was also studied for a 180-day period of anticipated contraceptive effect in 19 women. Alteration in menstrual cycle, with tendency to short bleeding episodes, spotting days, and amenorrhea were the most important collateral effects. In the majority of cases, ovulation was inhibited. No cases of pregnancy were presented. The obtained NET circulating levels were very stable during the period of anticipated contraceptive effect.     

Sulphation of contraceptive steroids

The sulphation of a number of contraceptive steroids by rabbit tissue in vitro was investigated. With liver tissue the three synthetic gestagens (norethisterone, norgesterel and lynestrenol) were sulphated at different rates and none was sulphated as rapidly as dehydroepiandrosterone; sulphation occurred at the tertiary 17 beta-hydroxyl group. The synthetic oestrogen ethynyloestradiol was sulphated more rapidly than dehydroepiandrosterone, both mono and disulphates being formed. Of the other tissues studied, sulphation occurred with stomach and lung but not with heart, spleen, muscle, kidney or adipose tissue. These in vitro studies provide confirmation of in vivo findings regarding sulphate conjugates of the synthetic steroids.     

Ligula intestinalis--a tapeworm contraceptive

Human contraceptives are 'big business', but might the real breakthrough come out from the pharmaceutical industry but from a tapeworm? Ligula intestinalis can induce infertility in infected fish of the carp family - both males and females. If the mechanism for this can be discovered, this humble flatworm could drastically change contraceptive practices with one pill for all.     

Progestin implants

Progestin implants for contraception are highly effective, safe, and the most convenient choice for many women. Progestin implants currently on the market, preparing for launch, or under investigation are reviewed here. Their basic galenic and pharmacokinetic features, as well as their contraceptive effectiveness, are described. The first progestin-only contraceptive implant placed on the market was Norplant, a multiunit system. Since then, several single- and double-rod implants have been developed, each using one of four different progestins: levonorgestrel, etonogestrel, Nestorone and nomegestrol acetate. Jadelle is similar to Norplant but consists of only two, rather than six, Silastic rods to simplify insertion and removal; nevertheless, levonorgesterel serum levels are identical, and performance is the same for both systems. The single implant systems reviewed here are: Implanon with a 3-year duration; Nestorone implants for breast feeding and non-breast feeding women lasting up to 2 years; and Uniplant, which is effective for 1 year. The advantages and disadvantages of progestin implants, the importance of counseling for increasing user satisfaction, and the future outlook for this contraceptive method are also discussed.     

The intrauterine contraceptive device.

This presentation brings into perspective the most recent information on intrauterine contraceptive devices. A comprehensive review of the literature is presented in a manner meaningful to the clinician. The advantages and disadvantages of this method of contraception, the problems that arise and the recommended methods of management are discussed. An updated review of the literature with regard to bleeding, pain, expulsion of the device, infection, uterine perforation and pregnancy is also presented.