Objectives (1) To identify pregnancies associated with the use of the contraceptive implants Implanon and Nexplanon in the UK during two 5-year reporting periods. (2) To classify the possible reasons for device failure in cases reported for each implant. (3) To examine any differences between reasons for pregnancies associated with these products.
Study design Extraction of data from the UK spontaneous reporting system for adverse drug reactions in relation to etonogestrel implants. Reports indicating pregnancy were identified for the periods 2005–2009 (Implanon) and 2012–2016 (Nexplanon). Possible reasons for failure of the method in each reported case were assigned to one of eight predetermined categories.
Results After exclusions, 229 Implanon and 234 Nexplanon cases contained sufficient information for analysis. True method failures accounted for a majority of the pregnancies in those using contraceptive implants (58%); the next most common cause was missing implants (26% of pregnancies). In all categories of cases, there was no difference in frequency of pregnancy when the two time periods were compared.
Conclusions There is still potential for greater avoidance of pregnancies associated with etonogestrel implant use.
Implications This study underscores the continuing need for taking a full drug history, timing the insertion on days 1–5 or according to recommended quick starting routines and palpating the arm after implant insertion.
- contraceptive implant
- drug interaction
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Presented at This study was first presented as a poster at the 18th Annual Meeting of the International Society of Pharmacovigilance, Geneva, Switzerland, November 2018.
Contributors SR conceived the idea for this study. All three authors contributed to the study design. EC extracted the data. All three authors were involved in the data analysis. SR wrote the first draft of the manuscript and all the three authors contributed to subsequent drafts. All three authors approved the final manuscript.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Disclaimer The content is solely the responsibility of the authors and does not necessarily represent the official views of the UK Medicines and Healthcare products Regulatory Agency.
Competing interests SR has received fees for acting as a trainer and for giving lectures on behalf of companies that market contraceptive implants.
Patient consent for publication Not required.
Ethics approval Not necessary. All data accessed were anonymised.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement All data relevant to the study are included in the article or uploaded as supplementary information.
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