In some cases implants may remain active for longer than this - therefore in the absence of withdrawal symptoms measure E2 levels. The recommended dose is 50mg oestradiol implant every 6 months. Most patients respond adequately to this dose. The 20mg implant is not often used for long term management. This is important if significant side effects such as mastodynia or migraines are predicted.
Some practitioners prefer to measure it before all doses.
Others feel that it does not need to be measured each time and that symptoms of hypo-oestrogenicity are a sufficient guide. If there is doubt about the activity of an implant, measurement of the E2 level at 2 - 4 weekly intervals may help in clinical management. This is an uncommon phenomenon with implant therapy. It is more likely to occur if implants have been inserted too frequently before E2 levels fall. Monitoring of plasma oestradiol levels is particularly helpful if symptoms are recurring sooner than expected.