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Comparative Study
. 2020 Dec;102(6):403-405.
doi: 10.1016/j.contraception.2020.08.011. Epub 2020 Aug 26.

Comparison of plasma etonogestrel concentrations sampled from the contralateral-to-implant and ipsilateral-to-implant arms of contraceptive implant users

Alida M Gertz  1 , Ian J Bishop  2 , Boikhutso Simon  3 , Kwana Lechiile  4 , Opelo Badubi  3 , Aamirah Mussa  3 , Carolyn L Westhoff  2 , Chelsea Morroni  5
Affiliations
Comparative Study

Comparison of plasma etonogestrel concentrations sampled from the contralateral-to-implant and ipsilateral-to-implant arms of contraceptive implant users

Alida M Gertz et al. Contraception. 2020 Dec.

Abstract

Objective: To compare plasma etonogestrel concentrations sampled from the contralateral- versus ipsilateral-to-implant arm.

Study design: Sub-analysis of a cross-sectional study in Botswana in 33 participants who provided contralateral and ipsilateral blood samples.

Results: Plasma etonogestrel concentrations in contralateral and ipsilateral specimens were highly correlated (correlation coefficient = 0.99; p < 0.0001). Bland-Altman analysis of agreement showed that etonogestrel levels were on average 5.9 pg/mL higher (2.1%) in ipsilateral compared to contralateral specimens (95% confidence interval: -4.1, 15.9 pg/mL).

Conclusions: We found no meaningful differences in plasma etonogestrel concentrations between samples taken from the contralateral- versus ipsilateral-to-implant arm.

Implications: Our data suggest that etonogestrel plasma concentrations are unlikely to be meaningfully different between samples drawn from the ipsilateral- versus the contralateral-to-implant arms in etonogestrel contraceptive implant users.

Keywords: Contraceptive implant; Contralateral arm; Etonogestrel; Ipsilateral arm; Pharmacokinetics.

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Figures

Fig. 1A.
Fig. 1A.
Plot of plasma etonogestrel concentrations (pg/mL) in contralateral versus ipsilateral arm samples in a sub-analysis of 33 participants in a pharmacokinetic study of the etonogestrel implant in Botswana. Each point on the plot represents an individual participant. The dotted line on the plot represents the hypothetical line of equality, where the ipsilateral concentration is exactly equal to the contralateral concentration for each participant. ENG, etonogestrel.
Fig. 1B.
Fig. 1B.
A Bland-Altman Plot for difference in plasma etonogestrel concentrations (pg/mL) comparing ipsilateral-to-implant to contralateral-to-implant samples in 33 participants in a pharmacokinetic study of the etonogestrel implant in Botswana. The Bland-Altman Plot is a plot of the difference between ipsilateral-to-implant and contralateral-to-implant etonogestrel concentrations against their mean. The mean difference was 5.9 (95% CI: −4.1, 15.9 pg/mL). The limits of agreement (i.e., −1.96sd to +1.96sd) are shown by the grey lines and range from −50.9 to 62.6 pg/mL. ENG, etonogestrel.
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