Progestogen-Only Implant

The progestogen-only implant is a small (4cm) flexible plastic rod that is placed in the upper arm, beneath the skin and above the subcutaneous fat. It slowly releases progestogen into the systemic circulation. It lasts for three years and then needs replacing.

The progestogen-only implant is more than 99% effective with perfect and typical use. Once in place, there is no room for user error. It needs to be replaced every three years to remain effective.

The progestogen-only implant has very few contraindications and risks. The only UKMEC 4 criteria for the implant is active breast cancer.

Nexplanon is the implant used in the UK. It contains 68mg of etonogestrel. It is licensed for use between the ages of 18 and 40 years.

 

Mechanism

The progestogen-only implant works by:

  • Inhibiting ovulation
  • Thickening cervical mucus
  • Altering the endometrium and making it less accepting of implantation

 

Insertion and Removal

Inserting the implant on day 1 to 5 of the menstrual cycle provides immediate protection. Insertion after day 5 of the menstrual cycle requires seven days of extra contraception (e.g. condoms), similar to the injection.

Specific qualifications are required to insert the implant. It is inserted one-third the way up the upper arm, on the medial side. Local anaesthetic (lidocaine) is used prior to inserting the implant. A specially designed device is used to insert the implant horizontally, beneath the skin and above the subcutaneous fat. It should be palpable immediately after insertion. Pressing on one end of the implant should make the other end pop upwards against the skin.

Specific qualifications are also required to remove the implant. Lidocaine is used as a local anaesthetic. The device is located, and a small incision is made in the skin at one end. The device is removed using pressure on the other end or forceps. Contraception is required immediately after it has been removed (but not immediately before).

 

Benefits

  • Effective and reliable contraception
  • It can improve dysmenorrhoea (painful menstruation)
  • It can make periods lighter or stop all together
  • No need to remember to take pills (just remember to change the device every three years)
  • It does not cause weight gain (unlike the depo injection)
  • No effect on bone mineral density (unlike the depo injection)
  • No increase in thrombosis risk (unlike the COCP)
  • No restrictions for use in obese patients (unlike the COCP)

 

Drawbacks

Several factors may limit the appeal of the implant:

  • It requires a minor operation with a local anaesthetic to insert and remove the device
  • It can lead to worsening of acne
  • There is no protection against sexually transmitted infections
  • It can cause problematic bleeding
  • Implants can be bent or fractured
  • Implants can become impalpable or deeply implanted, leading to investigations and additional management

 

Rarely the implant can become impalpable or deeply implanted. Women are advised to palpate the implant occasionally, and if it becomes impalpable, extra contraception is required until it is located. An ultrasound or xray may be required to locate an impalpable implant. They may need referral to a specialist removal centre. The manufacturer of Nexplanon adds barium sulphate to make it radio-opaque so that it can be seen on xrays.

In very rare cases there are reports of devices entering blood vessels and migrating through the body, including to the lungs. If the implant cannot be located even after an ultrasound scan, a chest xray may be considered to identify an implant in a pulmonary artery.

 

Bleeding Pattern

The FSRH guideline on the implant (2014) state approximately:

  • 1/3 have infrequent bleeding
  • 1/4 have frequent or prolonged bleeding
  • 1/5 have no bleeding
  • The remainder have normal regular bleeds

 

Problematic bleeding is managed similarly to the progestogen-only implant. The FSRH guidelines suggest the combined oral contraceptive pill (COCP) in addition to the implant for three months when problematic bleeding occurs, to help settle the bleeding (provided there are no contraindications).

 

Last updated August 2020
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