**5.2 Types**

There are several types of contraceptive implants on the market:


Of the various types of contraceptive implants available, the Implanon NXT®/ Nexplanon® is the most commonly used and is registered in approximately 80 countries worldwide [106]. It is radio-opaque (visible on X-ray) and has an improved insertion device.

#### **5.3 Mechanism of action**

Contraceptive implants have two primary mechanisms of action: inhibition of ovulation and restriction of sperm penetration [107]. The anti-estrogenic effect of the progestin causes the cervical mucus to become more viscous and scanty, thereby stopping sperm penetration and egg fertilization [108]. Furthermore, high doses of progestin diminishes gonadotropin secretion, inhibiting follicular maturation and ovulation. While progestin also suppresses endometrial activity by causing the endometrial thinning and atrophy, thereby impeding implantation, these two actions remain the major mechanisms of action in preventing fertilization [109]. There is no evidence of embryonic development among implant users, indicating that progestin implants have no abortifacient properties [81].

## **5.4 Effectiveness**

The etonogestrel implant (Implanon NXT®/Nexplanon®) is among the most effective and long-lasting contraceptives available and is as good as or better than sterilization procedures, with pregnancy protection rates of >99% for both typical and perfect users [88, 110]. If inserted within the first 5 days of the menstrual cycle, the implant is effective immediately after insertion, with peak serum levels occurring within 4 days [111]. The failure rate is negligible at <1 pregnancy per 100 women in the first year (or 1 per 1000 women). Beyond the first year of use, a small risk of pregnancy remains and continues as long as the client is relying on the implant as the only form of contraception.

The efficacy of implants is based on correct sub-dermal insertion and removal of the device. All healthcare providers should receive instructions and training prior to the insertion or removal of the implant. Women taking efavirenz for HIV should be advised to use condoms along with implants, as this medication may reduce the effectiveness of contraceptive implants.

### **5.5 Advantages**

Contraceptive implants are a highly effective, long-acting form of userindependent, non-coitus-related contraception that provides protection against pregnancy without the need for repeated adherence. Moreover, they have few side-effects and are rapidly reversible [100, 101]. Implants are a good option for adolescents, as they do not require the user to do anything after insertion and there is no need for routine follow-up visits, as well as for adult women who desire highly efficient, easy-to-use, long-term protection. Implants can be inserted without the need for a pelvic examination, breast examination, blood tests, or any other laboratory tests, barring another indication for doing so. Moreover, implants do not interfere with intercourse and clients are ensured of a complete return of fertility after removal.
