Progestogen-only Subdermal Implants (POSDI)

This is a long acting reversible contraceptive. Etonogestrel contained in a rod is released slowly into the systemic circulation following subdermal insertion in the upper arm.¹

Implanon® is now the only contraceptive implant on the UK market. It is a 4cm flexible rod containing 68 mg etonogestrel (a progestogen). Implanon® must be removed after 3 years when it can then be replaced.²
Norplant®, which consists of 6 small rods, has been available in the past in the UK. Along with Norplant-2 (also called Jadelle®) is still used in some countries.¹

The main mechanism of action of Implanon® is to inhibit ovulation. It also thickens the cervical mucus, inhibiting the passage of sperm to the uterus, as well as thinning the endometrium, preventing implantation were an egg to be fertilised.³

1% of women between the ages of 16 and 49 use the implant.⁴

Implanon® is suitable for those who want a reliable but reversible form of contraception which does not require daily vigilance like oral contraceptives or action at the time of intercourse like barrier contraceptives. It is a useful alternative for women who need a reliable form of contraception but who have contraindications to oestrogen therapy - another alternative is the injectable progestogen only contraception, depo-provera (given every 12 weeks).

All patients should be carefully counselled before insertion - supplemented by a suitable patient information leaflet.

Very low; most studies show no failures. NICE quote a failure rate of less than 1 in 1000 women in 3 years use.^1,5 The main reason for "failure" is incorrect timing of insertion, conception prior to insertion and failure of insertion.^3,6

• Pregnancy. Exclude pregnancy before insertion; a history of recent normal menstruation or reliable use of another contraceptive is adequate. If there is any doubt suggest urine pregnancy test pre-insertion.³
• Unexplained vaginal bleeding.
• Progesterone dependent cancers.
• Current hydatid mole or choriocarcinoma (until hCG undetectable).
• Current severe impairment of liver function (with abnormal LFTs) or history of liver adenoma or steroid induced cholestatic jaundice.
• History of severe arterial disease or very high risk factors. Although there is no evidence of increased risk with Implanon®, the manufacturer advises that it is avoided in those with current active venous thromboembolism.
• Hypersensitivity to any components of Implanon®.
  They share the contraindications of oral progesterone only contraceptives:²
  • Acute porphyria, even if no history of active disease.
  • Liver adenoma
  • Previous breast cancer - it can be used >5 years provided there is no evidence of reoccurrence.
• It may be less effective when given with:
  • Liver enzyme inducing drugs e.g. anti-epileptics.¹
  • Anti-retroviral drugs ™ the efficacy of both may be reduced, although the evidence on this is inconclusive.¹
  • Diabetes, breast feeding, migraine (with or without aura) and BMI >30kg/m² are not contraindications to using Implanon®, but because blood levels of etonogestrel may be lower in the 3rd year of use in women with a BMI >35kg/m², earlier than usual removal/replacement is recommended.

• Studies of women using Norplant® show very low rates of ectopic pregnancy. There are no studies of the effect of Implanon® on rates of ectopic pregnancy but because it inhibits ovulation it is presumed that the rates are very low.¹ It is therefore suitable for women who have a history of ectopic pregnancy.³
• Dysmenorrhoea usually improves while using Implanon®.^1,7
• There is no evidence of delay in return to fertility on removal of Implanon®.¹
• There is no evidence of reduced bone mineral density with Implanon®, unlike the contraceptive injection.³

• No protection is provided against sexually transmitted diseases.
• Unlike many methods of contraception, women cannot stop using an implant without the involvement of a properly trained health care professional. Removal of Implanon® is usually a straightforward minor operation under local anaesthetic. Possible complications include difficulty finding the rod and broken implants (frequency 0.2%). If the implant cannot be palpated, ultrasound examination should be carried out before removal as the implant may have been inserted deeply.
• As with other progesterone-only methods, a change in bleeding pattern (either amenorrhoea, irregular bleeding, menorrhagia ) is common and is the main reason for early removal of Implanon®. These changes do NOT settle with time. 33% of women have Implanon® removed early because of a change in bleeding pattern. If there are no contraindications, short term cyclical oestrogens (either as the combined oral contraceptive or as ethinyloestradiol), mefenamic acid and mifepristone may be of use in treating irregular or heavy bleeding. Counselling prior to insertion is important in decreasing discontinuation rates.^3,8,9,10
• Loss of libido and altered mood are rare side effects of Implanon®. The NICE guidelines recommend that these are not cited as side effects when counselling women.
• Acne may improve or worsen while using Implanon®.
• If pregnancy occurs during use of hormonal contraception, including combined oral contraceptives (COC), there is no evidence of increased risk of congenital malformation.¹¹ There is however a theoretic risk of virilisation of the fetus, so the implant should be removed as soon as possible.
• Nausea, vomiting, dizziness and mastalgia. Breast pain may be caused by Implanon®.
• Breast cancer incidence is slightly raised during and for up to 10 years after use of injectable contraceptives.

There is no evidence that Implanon® causes headaches, weight gain, increased blood pressure, increased risk of venous thromboembolism or changes in lipids or glucose. There is also some evidence of a lesser effect on the reduction in bone mineral density.

Pre-insertion counselling

• Always take a full medical history (family, menstrual, contraceptive and sexual history).¹¹
• Always give full counselling about the risks and benefits of the implant.
• Women should be advised to expect some discomfort and bruising at the site of insertion.
• Technically difficult insertions are unusual (<1 in 100).

Timing

• Implants may be inserted at any time in the menstrual cycle as long as the woman is "reasonably certain" that she is not pregnant. This includes those switching from another hormonal method of contraception.¹
• When switching from a levonorgestrel IUS the implant can be inserted immediately if the IUS was used correctly (or if the clinician is reasonably certain that the woman is not pregnant). The LNG-IUS should be continued for at least 7 days.¹²
• When switching from a copper IUD the implant may be inserted immediately if IUD was
  used correctly (or if the clinician is reasonably certain that the woman is not pregnant). The IUD should be continued for at least 7 days.
• If the patient is amenorrhoeic or if insertion occurs after day 5 of the menstrual cycle, extra, non hormonal contraceptive precautions should be taken for 7 days.^1,2
• After termination of pregnancy (TOP) in the first or second trimester, insertion may take place immediately.^1,12 If implanted > 5 days after abortion or miscarriage, additional contraception is required for 7 days.
• After pregnancy Implanon® should be inserted 21-28 days after delivery or TOP. It may be inserted immediately but this may be lead to an increase in irregular or heavy bleeding. If insertion takes place after day 28, additional contraception should be used for 7 days.¹

Insertion

Practical training is required. Family planning trained doctors will provide this, either in primary care or family planning clinics.

• After injection of local anaesthetic, Implanon® is inserted into the subdermal tissue of the upper arm (flexor surface).
• After insertion both the health professional and the patient should examine the arm and be satisfied that the implant is in place, thus reducing the risk of insertion failures.

Follow-up

• Unless the woman experiences problems, no follow up is required until removal is due 3 years after insertion.¹

EMIS would like to thank Dr Kate Johnson for the original draft of this article.