Question: Does Lamotrigine reduce the effectiveness of Implanon or vice versa?
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Answer: The Faculty of Sexual and Reproductive Healthcare published a statement in January on Antiepileptic Drugs and Contraception.(1) This says:
"Whilst no specific interaction studies have been performed with the etonogestrel-only implant(14) true failures have been reported in women using AEDs(15,16) and the SPC for Implanon® advises that efficacy may be affected."
(Evidence level III)
"There is evidence to suggest that progestogen-only methods do not affect lamotrigine and thus the use of progestogen only methods is not restricted with lamotrigine (UKMEC Category 1). A small trial(26) investigated any interaction between lamotrigine and combined (COC or vaginal ring) or progestogen-only contraception (i.e. POP, implant, DMPA or the LNG-releasing intrauterine system). Mean plasma concentrations of lamotrigine were significantly lower in CHC users (2.0 ± 1.3 mg/L) than controls (5.6 ± 3.1 mg/L) [p<0.001], but there was no statistically significant difference between levels in progestogen-only contraception users (5.4 ± 2.1 mg/L) and controls."
(Evidence level IIb)
Reference:
- Antiepileptic Drugs and Contraception. CEU Statement / Faculty of Sexual and Reproductive Healthcare Clinical Effectiveness Unit. 2010.
Search date: April 2010
Classification of evidence levels
Ia Evidence obtained from meta-analysis of randomised controlled trials.
Ib Evidence obtained from at least one randomised controlled trial.
IIa Evidence obtained from at least one well-designed controlled study without randomisation.
IIb Evidence obtained from at least one other type of well-designed quasi-experimental study.
III Evidence obtained from well-designed non-experimental descriptive studies, such as comparative studies, correlation studies and case studies.
IV Evidence obtained from expert committee reports or opinions and/or clinical experience of respected authorities.
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