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Contraceptive implants
Published in Suzanne Everett, Handbook of Contraception and Sexual Health, 2020
In 1993 Norplant was the first implant to be approved for use in the UK as a contraceptive. Norplant was licensed for five years, and is no longer manufactured. Norplant received a great deal of adverse media attention, after some women had problems with insertion and removal of the capsules; as a result Implanon was launched. However, many women were very happy with Norplant. Implanon was a single capsule reducing problems with insertion and removal. However, whilst Implanon was easier to fit and remove, the insertion procedure was slightly complicated; the manufacturers addressed this by developing Nexplanon in 2010. Nexplanon and Implanon are the same implants; however, the applicator and insertion technique for Nexplanon is more straightforward to ensure correct placement of the capsule, which is radiopaque. Nexplanon is now the only licensed implant in the UK. Nexplanon should always be inserted by professionals who have undergone the designated training for this device, to avoid problems with incorrect insertion and as a result difficulties with removal.
Birth control
Published in Frank J. Dye, Human Life Before Birth, 2019
Newer methods of chemical control of fertility use progestins introduced into the body by other routes. Two methods of applying hormonal control of reproduction are (1) intramuscular injections of medroxyprogesterone (Depo-Provera) every 3 months and (2) implants of levonorgestrel (Norplant), in the form of flexible, hormone-containing capsules, surgically placed under the skin of the upper arm. These capsules are effective for 5 years. Norplant was removed from the U.S. market because of serious side effects.
Migraine: diagnosis and treatment
Published in Stephen D. Silberstein, Richard B. Upton, Peter J. Goadsby, Headache in Clinical Practice, 2018
Stephen D. Silberstein, Richard B. Upton, Peter J. Goadsby
NorplantT, a system of subdermal implants that release a steady dose of levonorgestrel (a progestin), is an effective contraceptive that lasts 5 years. The primary side-effects are irregular menstrual bleeding and headaches. Headache, which was the primary reason cited for removal other than menstrual disturbance, occurs in about 5–20% of patients. Recently, Depo-ProveraT (medroxyprogesterone acetate suspension), a long-acting parenteral progestin, has been approved as a contraceptive agent. The exact frequency of headache with use of this drug is uncertain.
Drug delivery across length scales
Published in Journal of Drug Targeting, 2019
Derfogail Delcassian, Asha K. Patel, Abel B. Cortinas, Robert Langer
Implantable polymer devices have been in use since the 1970’s for longer term systemic drug delivery. Early examples included the Norplant® and Jadelle® non-degradable subcutaneous contraceptive implants, which provided controlled release of contraceptive hormones over 5 years. Early devices were composed of an implanted polymer-drug composite coated with a porous ethyl vinyl acetate membrane [42–44]. This membrane facilitated controlled kinetic release of the hormones and similar devices have been used to systemically deliver a range of pharmaceuticals including anti-inflammatory drugs and antibiotics [45–48]. As with the early Norplant® devices, many of these systems are based on non-degradable polymers with a fixed-rate delivery profile, controlled by drug diffusion from within the device. Devices are usually implanted, and removed, via a minor surgical procedure at the end of their delivery lifetimes. To minimise surgical intervention required in the removal of these devices, longer-acting, degradable subcutaneous rod implants are currently in development [49].
Drug eluting implants in pharmaceutical development and clinical practice
Published in Expert Opinion on Drug Delivery, 2021
Ashley R. Johnson, Seth P. Forster, David White, Graciela Terife, Michael Lowinger, Ryan S. Teller, Stephanie E. Barrett
Drug-eluting implants were first introduced for contraception in the 1990s [14]. Contraception is an ideal application of implant technology due to the potency of contraceptive hormones, extended treatment duration, and high risk of non-adherence [6]. An early contraceptive implant system was Norplant®, released by Wyeth Pharmaceuticals in 1991 [14]. Norplant® was a set of six silicone implants that were inserted into the upper arm to deliver medication over the course of five years. Multiple studies indicated that this system improved adherence to birth control and reduced unwanted pregnancies [4,6]. For example, in a study of approximately one hundred adolescents, 43% of participants discontinued oral birth control within six months, resulting in six pregnancies, whereas all Norplant users were adherent to medication and no pregnancies were observed throughout the trial period [6]. Since the release of Norplant®, significant effort has been devoted to reducing the number and size of implants required for sustained coverage. Norplant® was taken off the market partly due to difficulty in removal of the six implants and replaced with Bayer’s Jadelle® in 2008, which enabled five years of coverage with only two implants [15]. Implanon® (MSD) was approved for use in 1998 (in Indonesia) and in 2006 (in the USA) to provide three years of contraceptive coverage with a single implant [16]. The radioopaque second-generation Nexplanon®, including an optimized applicator for insertion, was released in 2011 [17]. Together, these technological improvements have reduced complications on implant removal (from 4.8% incidence for Norplant to <0.2% with Implanon®) [18].
Effects of progestin-only contraceptives on the endometrium
Published in Expert Review of Clinical Pharmacology, 2020
Carlo Bastianelli, Manuela Farris, Vincenzina Bruni, Elena Rosato, Ivo Brosens, Giuseppe Benagiano
Following these pioneering investigations, the effects of Norplant on uterine vasculature were further detailed, in an attempt to correlate its modifications with the occurrence of bleeding episodes. It has been already mentioned that irregular bleeding associated with the slow release of LNG occurs despite relatively high TF levels in the stromal compartment [28]. This increased expression involves both the epidermal growth factor (EGF) and PRs [104,155].