IMPLANON NXT IMPLANT ( Etornorgestrel 68mg)

Indications

• Contraception
• Management of heavy menstrual bleeding
• Endometriosis
• Hormonal replacement therapy

Dosage

Children: Refer to the BNF for Children for appropriate dosing recommendations based on age and specific clinical indications.

Adults: Refer to specific guidelines for dosing based on the formulation used, as doses may vary with different contraceptive methods. Continuous use often provides effective contraception when administered according to the manufacturer's instructions.

Mechanism of action

Etornorgestrel functions by binding to progesterone receptors, which leads to changes in gene expression and cellular activity. This results in the inhibition of gonadotropin secretion from the pituitary gland, preventing follicular maturation and ovulation. Additionally, it induces changes in the endometrial lining, making it less suitable for implantation, and thickens cervical mucus, which hinders sperm passage.

Pharmacodynamics

The primary pharmacodynamic effect of etornorgestrel is its ability to prevent ovulation. By suppressing luteinizing hormone (LH) and follicle-stimulating hormone (FSH) release, it prevents the physiological changes necessary for ovulation. Furthermore, it modifies the uterine lining and cervical mucus, enhancing its contraceptive effect. The progestational effects also contribute to menstrual cycle regulation in women using hormonal contraceptives.

Pharmacokinetics

Etornorgestrel is well absorbed after administration and has a bioavailability that varies based on the form of drug delivery. It is metabolized in the liver, predominantly through conjugation with glucuronic acid and sulfates, leading to its active metabolites. The elimination half-life is approximately 24 to 30 hours. It is excreted primarily in urine and feces, and its pharmacokinetic profile may be influenced by factors such as body weight and the use of other medications.

Contra-indications

• Pregnancy
• Active thromboembolic disorders
• History of severe liver disease
• Known or suspected hormone-sensitive malignancies
• Uncontrolled hypertension
• Undiagnosed vaginal bleeding
• Hypersensitivity to etonogestrel or any component of the formulation

Adverse effects

• Nausea
• Headache
• Breast tenderness
• Mood changes
• Weight gain
• Menstrual irregularities
• Acne
• Decreased libido
• Abdominal pain

Interactions

• Anticonvulsants (e.g., phenytoin, carbamazepine, topiramate)
• Antibiotics (e.g., rifampicin, rifabutin)
• St. John's Wort
• HIV medications (e.g., ritonavir)
• Herbal supplements that induce liver enzymes

Precautions

• Monitor for signs of thromboembolism
• Assess for hypertension prior to initiation
• Evaluate liver function before prescribing
• Consider alternative contraceptive methods in patients with gastrointestinal disorders affecting absorption
• Use with caution in patients with a history of depression

Pregnancy

Etonogestrel is contraindicated during pregnancy. If pregnancy occurs during treatment, the device should be removed.

Breast-feeding

Etonogestrel can be used during breastfeeding. It is secreted in breast milk but is considered safe for use.

Storage

Store at room temperature, away from light and moisture. Do not freeze. Keep out of reach of children.

Formulations

• Implant (etonogestrel 68 mg) for subdermal insertion
• Vaginal ring (etonogestrel 0.12 mg/day)