From the Guidelines
The progesterone-only pill (POP) should be taken within 3 hours either side of your usual time (18:00) to maintain its contraceptive effectiveness. This means you can take it as early as 15:00 or as late as 21:00 without compromising protection. The traditional progesterone-only pill works primarily by thickening cervical mucus to prevent sperm from reaching an egg and, in some women, by inhibiting ovulation. According to the U.S. selected practice recommendations for contraceptive use, 2013 1, a dose is considered missed if it has been >3 hours since it should have been taken. Key points to consider when taking the progesterone-only pill include:
- Taking one pill as soon as possible if a dose is missed
- Continuing to take pills daily, one each day, at the same time each day, even if it means taking two pills on the same day
- Using backup contraception (e.g., condoms) or avoiding sexual intercourse until pills have been taken correctly, on time, for 2 consecutive days
- Considering emergency contraception if unprotected sexual intercourse has occurred The importance of taking the pill at approximately the same time each day is highlighted by the fact that peak serum steroid levels are reached about 2 hours after administration, followed by rapid distribution and elimination, such that by 24 hours after administration, serum steroid levels are near baseline 1. If you take your pill outside this 3-hour window, you should use additional contraception (like condoms) for the next 48 hours while continuing to take your pills at the regular time.
From the Research
Effectiveness of Progesterone Only Pill
- The provided studies do not directly address the effectiveness of the progesterone only pill when taken at 18:00 every day 2, 3, 4, 5, 6.
- The studies focus on the comparison of levonorgestrel and copper intrauterine devices for emergency contraception 2, 3, the effects of copper-releasing intrauterine devices or levonorgestrel-releasing intrauterine systems on uterine bleeding and iron status 4, and the continuation of copper or levonorgestrel intrauterine devices initiated at the time of emergency contraception 5.
- There is no information on the specific time frame of effectiveness for the progesterone only pill when taken at a consistent time every day.
Time Frame of Effectiveness
- Since the studies do not provide direct information on the time frame of effectiveness for the progesterone only pill, it is not possible to determine the exact number of hours either side of 18:00 that the contraceptive will be effective 2, 3, 4, 5, 6.
- The effectiveness of the progesterone only pill may depend on various factors, including the individual's hormonal balance and the timing of ovulation, but this information is not provided in the studies.
Conclusion on Available Information
- Based on the available studies, there is no direct information to answer the question about the time frame of effectiveness for the progesterone only pill when taken at 18:00 every day 2, 3, 4, 5, 6.
- Further research would be needed to determine the specific time frame of effectiveness for the progesterone only pill.