Nexplanon is a long-acting reversible contraceptive (LARC) implant designed to prevent pregnancy for up to three years. This small, flexible rod, about the size of a matchstick, is placed discreetly under the skin of the upper arm. For individuals considering this method, a common question involves understanding how quickly Nexplanon begins to offer protection against pregnancy.
When Nexplanon Becomes Effective
The timeline for Nexplanon’s effectiveness depends on when it is inserted during a person’s menstrual cycle. If placed within the first five days of your menstrual period (day one is the first day of bleeding), protection against pregnancy begins immediately. If Nexplanon is inserted at any other point, a seven-day waiting period is necessary for it to become fully effective, as it takes this time for the implant to establish sufficient hormone levels. During this seven-day period, use a backup method of contraception. Healthcare providers will offer specific guidance based on your individual circumstances and the timing of the insertion.
How Nexplanon Prevents Pregnancy
Nexplanon works by continuously releasing a low dose of etonogestrel, a synthetic progestin hormone, into the bloodstream, preventing pregnancy through multiple mechanisms. One of its primary actions is to stop ovulation, preventing the ovaries from releasing an egg. Without an egg available for fertilization, pregnancy cannot occur. The progestin also significantly thickens the cervical mucus, creating a physical barrier that makes it challenging for sperm to travel through the cervix and reach an egg. Additionally, Nexplanon causes changes to the lining of the uterus, making it thinner and less receptive to the implantation of a fertilized egg, making Nexplanon a highly effective form of contraception, with an effectiveness rate of over 99%.
Situations That May Delay Effectiveness
Certain circumstances can potentially alter or delay Nexplanon’s expected effectiveness.
Insertion Timing
Insertion outside the recommended window during the menstrual cycle necessitates a seven-day backup contraception period. Failing to use backup contraception during this time can increase the risk of pregnancy.
Medication Interactions
Interactions with certain medications can also reduce the implant’s efficacy. Some antibiotics, specifically rifampin and griseofulvin, can cause the body to break down etonogestrel more quickly, leading to lower hormone levels and potentially reduced protection. Similarly, some anti-seizure medications, such as carbamazepine, topiramate, and phenytoin, can interfere with Nexplanon’s hormone metabolism. The herbal supplement St. John’s Wort is another known substance that can diminish Nexplanon’s effectiveness. It is important to inform your healthcare provider about all medications, supplements, and herbal remedies you are taking to assess for potential interactions.
Using Backup Contraception
When Nexplanon is inserted outside the first five days of your menstrual period, using a backup method of contraception is necessary for the initial seven days. During this week, consistent use of a barrier method, such as condoms, provides protection against pregnancy while the implant reaches its full effectiveness. This minimizes the risk of an unintended pregnancy during the transition period. If you are switching from another hormonal birth control method, your healthcare provider will advise on whether to continue your previous method for a short period or use backup contraception. Always follow your provider’s specific instructions for using backup contraception, and should you have any concerns about the implant’s effectiveness or if you cannot feel the implant in your arm, contact your healthcare professional immediately and use a non-hormonal birth control method.