Note: The prescribing information of concomitant medications should be consulted to identify potential interactions.
Influence of other medicinal products on Implanon NXT: Interactions between hormonal contraceptives and other medicinal products may lead to breakthrough bleeding and/or contraceptive failure.
The following interactions have been reported in the literature (mainly with combined contraceptives but occasionally also with progestagen-only contraceptives).
Hepatic metabolism: Interactions can occur with medicinal or herbal products that induce microsomal enzymes, specifically cytochrome P450 enzymes (CYP), which can result in increased clearance, reducing plasma concentrations of sex hormones and may decrease the effectiveness of Implanon NXT. These products include phenytoin, barbiturates, primidone, bosentan, carbamazepine, rifampicin, and possibly also oxcarbazepine, topiramate, felbamate, griseofulvin, some HIV protease inhibitors (e.g. ritonavir) and non-nucleoside reverse transcriptase inhibitors (e.g. efavirenz), and the herbal remedy St. John's wort.
Enzyme induction can occur after a few days of treatment. Maximum enzyme induction is generally observed within a few weeks. After drug therapy is discontinued, enzyme induction can last for about 28 days.
When co-administered with hormonal contraceptives, many combinations of HIV protease inhibitors (e.g. nelfinavir) and non-nucleoside reverse transcriptase inhibitors (e.g. nevirapine), and/or combinations with HCV medicinal products (e.g. boceprevir, telaprevir), can increase or decrease plasma concentrations of progestins, including etonogestrel. The net effect of these changes may be clinically relevant in some cases.
Women receiving any of the previously mentioned hepatic enzyme-inducing drugs or herbal products should be advised that the efficacy of Implanon NXT may be reduced. If it is decided to continue using Implanon NXT, women should be advised to also use a non-hormonal contraceptive method during the time of concomitant drug administration and for 28 days after discontinuation.
Concomitant administration of strong (e.g. ketoconazole, itraconazole, clarithromycin) or moderate (e.g. fluconazole, diltiazem, erythromycin) CYP3A4 inhibitors may increase the serum concentrations of progestins, including etonogestrel.
Influence of Implanon NXT on other medicinal products: Hormonal contraceptives may interfere with the metabolism of other drugs. Accordingly, plasma and tissue concentrations may either increase (e.g., cyclosporin) or decrease (e.g., lamotrigine).
Laboratory parameters: Data obtained with combined OCs have shown that contraceptive steroids may affect some laboratory parameters, including biochemical parameters of liver, thyroid, adrenal and renal function, serum levels of (carrier) proteins, e.g., corticosteroid binding globulin and lipid/lipoprotein fractions, parameters of carbohydrate metabolism and parameters of coagulation and fibrinolysis. The changes generally remain within the normal range. To what extent this also applies to progestagen-only contraceptives is not known.
Magnetic Resonance Imaging (MRI) Safety Information: Implanon NXT is MR safe.