What it's for (Indications)
- Levonorgestrel is a synthetic progestin primarily indicated as an emergency contraceptive (EC), often referred to as a 'morning-after pill,' for the prevention of pregnancy following unprotected sexual intercourse or a known or suspected contraceptive failure.
- It is intended for occasional, not routine, use.
- For optimal efficacy, levonorgestrel emergency contraception should be administered as soon as possible within 72 hours (3 days) of unprotected intercourse.
- While some data suggest it may retain some effectiveness up to 120 hours (5 days), its effectiveness significantly decreases with increasing time post-coitus.
- Beyond its role in emergency contraception, levonorgestrel is also extensively utilized in various forms of ongoing contraception, including progestin-only oral contraceptive pills (mini-pills), subdermal implants, and intrauterine systems (IUS), where it provides long-term, highly effective pregnancy prevention by different mechanisms.
- The specific indication for a given formulation (e.
- g.
- , Emkit for EC) dictates its precise use.
- It is not indicated for the termination of an existing pregnancy.
Dosage Information
| Type | Guideline |
|---|---|
| Standard | For emergency contraception, the standard dosage of levonorgestrel (e.g., Emkit) is a single oral dose of 1.5 mg, taken as soon as possible within 72 hours (3 days) after unprotected intercourse. Alternatively, some older formulations may consist of two 0.75 mg tablets, with the second tablet taken 12 hours after the first. However, the single 1.5 mg dose regimen has largely become the preferred and most commonly available method due to its comparable efficacy and improved compliance. It is crucial to emphasize that delaying administration beyond 72 hours significantly reduces its effectiveness, although it may still offer some benefit up to 120 hours, with a continuous decline in efficacy over time. This medication is not intended for regular use as a primary method of contraception and should not be used as such. If vomiting occurs within two hours of taking the dose, a healthcare professional should be consulted to determine if another dose is necessary, as the dose may not have been fully absorbed. |
Safety & Warnings
Common Side Effects
- Common side effects associated with levonorgestrel emergency contraception are generally mild and transient, typically resolving within 24 to 48 hours.
- These frequently include nausea, which may be mild to moderate, lower abdominal pain or cramping, fatigue, headache, and dizziness.
- Breast tenderness and irregular menstrual bleeding or spotting are also commonly reported, and the next menstrual period may occur earlier or later than expected, and may be heavier or lighter than usual.
- While rare, more serious adverse effects can occur.
- Persistent or severe lower abdominal pain, especially if accompanied by fainting, weakness, or shoulder pain, should prompt immediate medical evaluation, as it could be a symptom of an ectopic pregnancy (pregnancy outside the uterus), which is a serious medical emergency, particularly if the emergency contraception has failed.
- Allergic reactions, though uncommon, are also possible, characterized by rash, itching, swelling (especially of the face, tongue, or throat), severe dizziness, or trouble breathing, and require immediate medical attention.
Serious Warnings
- Black Box Warning: **Serious Warnings** Levonorgestrel, including emergency contraceptive products like Emkit, does not carry a formal FDA Black Box Warning. However, several critical safety considerations warrant serious attention from users and healthcare providers to ensure its safe and appropriate use. It is imperative to understand that this medication is explicitly designed for *emergency contraception* and is not to be used as a regular or primary method of birth control. Its repeated use within a single menstrual cycle is not advised and may lead to unpredictable menstrual irregularities with uncertain cumulative efficacy. Levonorgestrel offers absolutely no protection against sexually transmitted infections (STIs), including HIV/AIDS; barrier methods remain essential for STI prevention. A significant warning concerns the risk of ectopic pregnancy: if pregnancy occurs despite taking levonorgestrel, the possibility of an ectopic pregnancy must be considered, especially in the presence of severe abdominal pain, fainting, or shoulder pain. Ectopic pregnancies are medical emergencies that require prompt diagnosis and intervention. Furthermore, levonorgestrel does not terminate an existing pregnancy and is not an abortifacient. Patients should be counselled on these critical aspects to ensure safe and appropriate use and to manage expectations regarding efficacy and side effects.
- Levonorgestrel emergency contraception comes with several important warnings that users and healthcare providers must understand.
- This medication is not intended for routine use as a regular birth control method; repeated use within a single menstrual cycle is not recommended due to potential disruption of the menstrual cycle and uncertain cumulative efficacy.
- It does not protect against sexually transmitted infections (STIs), including HIV/AIDS, and alternative barrier methods (e.
- g.
- , condoms) should be used for STI prevention.
- If pregnancy occurs despite taking levonorgestrel, there is a risk of ectopic pregnancy, which can be life-threatening; thus, any persistent or severe abdominal pain post-treatment warrants immediate medical assessment to rule out an ectopic pregnancy.
- Furthermore, levonorgestrel does not terminate an existing pregnancy; it is not an abortifacient.
- Efficacy may be reduced in individuals with higher body mass index (BMI), though research on this is conflicting and ongoing.
- Concomitant use of certain medications, such as potent CYP3A4 enzyme inducers (e.
- g.
- , barbiturates, bosentan, carbamazepine, efavirenz, phenytoin, rifampin, St.
- John’s Wort, topiramate), can significantly decrease the effectiveness of levonorgestrel and should be discussed with a healthcare provider.
- Patients with a history of severe liver impairment or undiagnosed abnormal vaginal bleeding should exercise caution and seek medical advice before use.
How it Works (Mechanism of Action)
Levonorgestrel, as a synthetic progestin, primarily exerts its contraceptive effects by preventing ovulation. When taken as emergency contraception in a high dose, it acts by inhibiting the luteinizing hormone (LH) surge, which is essential for follicular rupture and subsequent release of an egg from the ovary. By suppressing or delaying ovulation, it prevents the sperm from encountering an egg, thus averting fertilization. In addition to its impact on ovulation, levonorgestrel may also induce changes in the endometrium (the lining of the uterus), making it less receptive to implantation, and thicken cervical mucus, which impedes sperm migration through the cervix. It is crucial to understand that levonorgestrel does not work if implantation has already occurred; it is not an abortifacient and will not terminate an established pregnancy. Its mechanism is therefore predominantly pre-fertilization or pre-implantation. For continuous contraception (e.g., implants, IUS, mini-pills), its ongoing presence consistently suppresses ovulation, maintains thickened cervical mucus, and thins the uterine lining to prevent pregnancy.