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How Long Does “Plan B” Stay In Your System?

“Plan B” is a brand name birth control formulation manufactured in tablets, each of which contains 0.75 mg of the active steroid levonorgestrel. Levonorgestrel is an entirely synthetic progestogen that was synthesized in the 1960s and was included in birth control products by the 1980s.  The levonorgestrel within Plan B functions by inhibiting ovulation or fertilization by modifying tubal transport of sperm and/or ova.

Some speculate that it may also decrease endometrial receptivity to the implantation of a fertilized egg.  Though administration of Plan B is not regarded as a clinically effective intervention post-uterine implantation, it is suggested to work for up to 72 hours following unprotected sex.  In the United States, Plan B is ubiquitously available as an over-the-counter emergency contraceptive for those over the age of 16, and was used by 11% of sexually active women between the years 2006 and 2010.

As a result of its efficacy and popularity, it is regarded as an “essential medicine” by the World Health Organization (WHO).  Though an incredibly useful and practical medication, Plan B can provoke unwanted side effects such as: breast tenderness, headaches, menstrual irregularities, and nausea.  The combination of lingering side effects along with general curiosity has lead many women to ask how long “Plan B” stays in their system after taking it.

  • Source: http://www.cdc.gov/nchs/data/databriefs/db112.htm

How long does “Plan B” stay in your system?

To determine how long “Plan B” is likely to stay in your system, it is necessary to examine the elimination half-life of its principal ingredient Levonorgestrel.  Levonorgestrel is reported to have an elimination half-life of 24.4 hours (+/- 5.3 hours).  This indicates that the average Plan B user will have eliminated 50% of the dosage from systemic circulation in just over a day after ingestion.

Knowing the average half-life of 24.4 hours, we can estimate that it’ll take around 5.59 days to completely clear a single Plan B dose from your system.  However, research has suggested that there’s an approximate 5.3 hour deviation in elimination half-life among most users.  This indicates that some users may exhibit half-lives closer to 19.1 hours, while others may exhibit half-lives closer to 29.7 hours.

Those with faster elimination half-lives of 19.1 hours could clear Plan B from their systems within 4.38 days, while those with slower elimination half-lives could eliminate Plan B within 6.81 days.  In other words, most people taking Plan B will have eliminated the levonorgestrel from systemic circulation within a week after single-dose administration.  Sources other than the Plan B product labeling suggest that the elimination half-life may be slightly longer than 24.4 hours.

Independent research has suggested an elimination half-life of 28 hours (+/- 6.4 hours) and other evidence suggests that from steady state concentrations, 36 hours (+/- 13 hours) may be more accurate.  From the 28 hour half-life with the (+/-) 6.4 hour deviations, we could estimate that elimination may take 6.42 days (on average), but possibly sooner in 4.95 days or later in 7.88 days.  If steady state concentrations were attained, average elimination could take 8.25 days (on average), but possibly less time (5.27 days) or a much longer duration (11.23 days).

Most users of Plan B should therefore conclude that the drug is unlikely to still be in their systems after 2 full weeks.  Even in the extreme cases of users experiencing a prolonged elimination half-life of 49 hours, the drug should have been eliminated in under 12 days.  In summary, most Plan B users will have eliminated the synthetic hormone within 1 week.

  • Source: http://ec.princeton.edu/pills/PlanBLabeling.pdf
  • Source: https://pubchem.ncbi.nlm.nih.gov/compound/Levonorgestrel

Variables that influence how long Plan B stays in your system

Though Plan B’s labeling indicates that most individuals should eliminate the levonorgestrel from their system in 5.59 days (on average), it does suggest that there is usually some variation in half-life.  When contemplating whether Plan B is likely to stay in your system for a shorter or longer duration than average, it is necessary to consider some variables.  Variables that influence how long Plan B stays in your system include: dosage, frequency of administration, individual attributes, and co-administered drugs.

  1. Dosage of Plan B

The dosage of Plan B that you administer can affect how long it stays in your system.  As with most drugs, the greater the dosage you ingest, the longer you can expect it to stay in systemic circulation.  Whereas the lower the dosage of Plan B you take, the quicker you can expect it to leave your system (as a general rule of thumb).

Reports suggest that when levonorgestrel (the active synthetic steroid within Plan B) is administered at low doses such as 0.15 mg or 0.25 mg, its half-life is considerably reduced compared to that of a standard 0.75 mg dose.  Half-lives of 0.15 mg and 0.25 mg doses were reported at 13.2 hours and 9.9 hours, respectively.  Knowing this information we would estimate an average elimination term of 2.27 to 3.02 days following low-dose administration.

If administered at a dosage greater than is medically intended, the half-life of levonorgestrel is likely to exceed its average of 24.4 hours.  In other words, someone taking multiple Plan B pills simultaneously or within a short duration may retain the levonorgestrel in circulation for longer than a standard dose user.  That said, even if a person were to take three Plan B pills, the levonorgestrel is likely to be eliminated in under 2 weeks.

  1. Frequency of administration

The frequency at which you take Plan B will also affect how long it stays in your system.  Someone who takes Plan B every single night is likely to retain the levonorgestrel content for a markedly longer term than a person who takes levonorgestrel only in the case of emergencies.  Therefore if you use Plan B more frequently than “just emergencies,” there’s a chance that it may accumulate within your body to a greater extent, leading to a prolonged elimination term.

On the other hand, a person who uses Plan B only in the case of infrequent emergencies (as is medically intended), the levonorgestrel should be eliminated in under 6 days (on average).  Increased frequency of administration elevates serum concentrations of levonorgestrel, resulting in increased likelihood of levonorgestrel accumulation within bodily tissues.  Should levonorgestrel accumulate in bodily tissues of frequent users, its elimination half-life is likely to be prolonged.

Research already shows that steady state concentrations of levonorgestrel are attained within 9 days of administration and that the steady state half-life is prolonged.  Should you have taken Plan B for over 9 days straight, it’ll likely take between 1 and 2 weeks to eliminate levonorgestrel from your system after discontinuation.  In addition to accumulation in serum and bodily tissue, it is possible that frequent administration is more taxing on hepatic and renal function.

If you were to take Plan B frequently, there’s a chance that hepatic metabolism would be less efficient than usual as a result of the increased quantity of levonorgestrel ingested (as a result of frequent dosing).  This increased quantity of levonorgestrel would likely tax hepatic enzymes and decrease the efficiency of metabolism, leading to prolonged elimination.  Furthermore, increased frequency of administration will yield a greater number of levonorgestrel metabolites circulating throughout your system at a time – all of which will necessitate excretion.

The heighted number of metabolites among frequent users of Plan B may tax the kidneys to a greater extent, thereby diminishing excretion speed.  If you use Plan B on an infrequent basis, the levonorgestrel should be eliminated with efficiency in under 6 days.  However, if you’re a frequent user that may have attained steady state concentrations, expect it to remain in your system for a longer period (possibly up to 2 weeks).

  • Source: http://www.ncbi.nlm.nih.gov/pubmed/1458892
  1. Individual factors

Hypothetically speaking, two women could simultaneously ingest a single-dose of Plan B, yet the exact elimination speed among these women would likely differ.  The difference in elimination speed may be minor (e.g. a matter of minutes), but could also be more significant (e.g. many hours).  These differences in elimination speeds are typically dictated by individual factors such as a person’s body mass, genetics, hepatic function, and renal function.

Body mass + Fat (%): It is understood that levonorgestrel is highly lipophilic, meaning it is soluble in fat.  This makes it increasingly likely to accumulate among users that are obese and/or have a high percentage of body fat, especially when administered frequently over an extended term.  Should woman with a high BMI take levonorgestrel daily for several weeks, her elimination term would likely exceed the elimination term of a woman with a low BMI.

This is because the woman with a low BMI will experience altered distribution, protein binding, metabolism, and renal excretion of levonorgestrel compared to the high BMI user.  Furthermore, propensity of levonorgestrel accumulation will be reduced among women with low BMIs because there are fewer fat stores to retain levonorgestrel for an extended duration.  Though differences in half-lives among obese and non-obese Plan B users may not always be clinically significant, they will likely differ.

  • Source: https://books.google.com/books?id=ZjzdazsyRVoC
  • Source: http://www.ncbi.nlm.nih.gov/pubmed/25528415
  • Source: http://www.ncbi.nlm.nih.gov/pubmed/3315402

Genetics: Though the exact pharmacokinetics of levonorgestrel haven’t been elucidated in humans, it is metabolized by CYP450 (cytochrome P450) hepatic enzymes.  Since it is understood that alleles of CYP-genes influence the function of CYP450 enzymes, it is likely that metabolism of levonorgestrel may differ among users based on CYP alleles.  Though researchers initially speculated that CYP3A4*1B and CYP3A5*3 polymorphisms may alter metabolism and elimination of levonorgestrel, no conclusive evidence supports this speculation.

However, researchers did note that there was significant interindividual variability in plasma concentrations of levonorgestrel, some of which is likely a result of allelic polymorphisms.  Therefore it is necessary to consider that certain polymorphisms of CYP450-genes may dictate the metabolism, serum concentrations, and half-life of levonorgestrel.  A poor metabolizer of Plan B as a result of decreased CYP450 function (stemming from allelic expression) would likely exhibit an increase in levonorgestrel half-life, eliminating it at a slower than average pace.

It appears as though levonorgestrel significantly inhibits CYP1A2 function, so perhaps individuals with poorer CYP1A2 function (as a result of alleles associated with their CYP1A2 gene) may retain the drug for a longer duration.  An individual with optimal expression of the isoenzymes required to metabolize levonorgestrel would be classified as a rapid metabolizer, and may excrete the drug at a quicker rate.

  • Source: http://www.ncbi.nlm.nih.gov/pubmed/23715232

Hepatic function: The degree to which your liver is healthy may also impact the duration Plan B is likely to stay in your system.  A person with hepatic impairment as a result of a condition like cirrhosis is unlikely to efficiently metabolize levonorgestrel.  This poor metabolism of levonorgestrel is likely to increase serum concentrations and contribute to prolonged elimination after administration.

Individuals with compromised hepatic function will exhibit reductions in CYP450 enzyme function.  Usually this reduction in enzymatic function of CYP450 is directly proportional to the degree of hepatic impairment.  A person with mild hepatic impairment may retain levonorgestrel for slightly longer than average, whereas an individual with severe hepatic impairment may retain levonorgestrel for substantially longer than average.

Metabolic rate: A person’s BMR (basal metabolic rate) is likely to have a slight influence on how long Plan B stays in their system.  If you have a high BMR, it is known that your body is essentially burning more energy in a resting state than someone with a low BMR.  This increased energy expenditure tends to expedite metabolism and elimination of exogenous substances.

In cases of hyperthyroidism associated with an extremely high BMR, drugs are often eliminated substantially quicker than average.  In cases of hypothyroidism associated with a low BMR, drugs are eliminated slower than average.  Though most users are unlikely to be at the extremes of BMR associated with thyroid dysfunction, whether you have a high or low BMR may have a modest impact on levonorgestrel elimination.

Other drugs: It is well-documented that levonorgestrel interferes with the metabolism of other drugs, but on the flipside, it is important to acknowledge that other agents (whether it be drugs or supplements) could alter the metabolism of levonorgestrel.  Since levonorgestrel is thought to be metabolized by CYP450 isoenzymes such as CYP3A4 and CYP1A2 – any co-administered agent that affects the function of the aforementioned isoenzymes will alter the kinetics of levonorgestrel.

A drug that serves to interfere with CYP3A4, CYP3A5, or CYP1A2 function would be classified as an “inhibitor.”  Examples of respective inhibitors of CYP3A4 and CYP1A2 include: Ritonavir and Luvox.  If you were to take a CYP3A4 or CYP1A2 inhibitor along with Plan B, there’s a chance that the drug would remain in your system for longer than usual as a result of altered metabolism.

Conversely, a drug that enhances function of these various isoenzymes would be considered an “inducer.”  Examples of respective inducers of CYP3A4 and CYP1A2 include: Modafinil and tobacco.  Should you have taken an inducer along with Plan B, it may expedite metabolism of levonorgestrel leading to faster elimination.

Renal function: A majority of each Plan B dosage is excreted via the kidneys.  If you have compromised renal function, it is possible that you may retain levonorgestrel metabolites for a longer duration than usual.  Renal impairment is known to cause accumulation of exogenous substances prior to their elimination, potentially contributing to reabsorption and redistribution throughout the body.

The extent to which your kidney function is impaired may be reflective upon how long Plan B stays in your system.  Someone with a mild form of renal impairment may eliminate levonorgestrel with relative efficiency compared to someone with more significant impairment.  If your kidney function is optimal, excretion of levonorgestrel metabolites should remain efficient.

Plan B: Absorption, Metabolism, Excretion (Details)

Following oral administration of Plan B, its synthetic steroid “levonorgestrel” is rapidly absorbed with a bioavailability of approximately 100%.  In around 1.6 hours after ingestion, plasma concentrations of levonorgestrel peak at approximately 14.1 ng/ml.  Up to 99% of levonorgestrel binds to plasma proteins, particularly sex hormone binding globulin (SHBG) and albumin, and is distributed at a volume of 1.8 liters per kilogram.

Unlike many pharmaceutical drugs, it is not subject to extensive hepatic first-pass metabolism.  However, some of the levonorgestrel is broken down by CYP450 isoenzymes and undergoes reduction of the delta-4 and 3-oxo group, as well as hydroxylation at 2-alpha, 1-beta, and 16-beta positions.  This is followed by conjugation at the 17-beta-OH position to facilitate formation of sulfates and (to a lesser extent) glucuronides.

In humans, the notable metabolites within plasma derived from levonorgestrel include (conjugated and unconjugated) sulfates:

  • 3-alpha,5-beta-tetrahydrolevonorgestrel
  • 3-alpha,5-alpha-tetrahydrolevonorgestrel
  • 16-beta-hydroxynorgestrel

The combination of these three metabolites is equal to less than 10% of parent (levonorgestrel) levels within the plasma.  These metabolites are then subject to renal excretion, with 45% being eliminated within urine and 32% within feces.  Systemic plasma elimination of Plan B should take around 5.59 days, but complete excretion via urine and feces may exceed this duration.  Most users taking Plan B once should expect to have fully excreted the drug in under 2 weeks.

Tips to clear Plan B from your system

If you’re looking to eliminate Plan B from your system as soon as possible, there may be some tricks that can be used.  It is necessary to caution that none of these tips should be implemented immediately after taking Plan B.  Furthermore, should you consider implementing any of the strategies below as a means of detoxification, you should first confirm safety and alleged efficacy with a medical professional.

  1. Physical exercise: Perhaps the least harmless suggestion here is to ramp up physical exercise in attempt to burn body fat. Though short-term fat burning is unlikely to have significant implications for the pharmacokinetics of Plan B, it may slightly expedite the elimination of levonorgestrel and its metabolites. This may be especially helpful for women who have a high percentage of body fat that may have taken Plan B for a long duration (as to accumulate levonorgestrel within adipose tissue).
  2. Calcium-d-glucarate: The supplement calcium-d-glucarate may aid in the renal excretion of Plan B, providing your kidneys with extra support. Calcium-d-glucarate acts as a beta-glucuronidase inhibitor which essentially allows for the clearance of molecules within detoxification pathways. Though this may not dramatically improve renal excretion speed of Plan B, it will likely aid in general detoxification.
  3. Activated charcoal: Another supplement to consider whenever discontinuing any drug that you believe is still in your system is to take activated charcoal. Should any Plan B have accumulated within your body to a significant extent, activated charcoal will bind to it and/or toxins that it may have created. Always ask your doctor when it is safe to take activated charcoal as this supplement can interfere with absorption of other medications you may be taking.
  4. Modification of pH: The degree to which Plan B is acid labile is unknown. However, it could be hypothesized that acidification of urinary pH may expedite the elimination of levonorgestrel from your system. Acidification of urine can be accomplished via dietary modifications and/or ingestion of supplements to deliberately increase pH.  If Plan B happens to be acid labile, much of the drug may be destroyed in an acidic environment and urinary excretion may be expedited.

How long has Plan B stayed in your system after stopping?

If you took Plan B, share a comment mentioning how long you believe it stayed in your system.  Do you think that the levonorgestrel component lingered in your system for longer than 6 days?  Or do you think that you were able to eliminate most of it in a shorter duration?  Many women speculate that Plan B stays in their body for longer than is medically reported due to the side effects that are experienced.

While there is some variation in elimination time among users (possibly by several days), in the vast majority of Plan B users, it should be out of the plasma within 1 to 2 weeks after cessation.  In the event that a woman were to ingest high doses of Plan B frequently for a long-term, it could take longer than 2 weeks to eliminate from the plasma.  Since most women take standard dosages within proper medical guidelines, elimination shouldn’t be protracted.

If you suspect that Plan B may still be in your system due to the fact that you’re still experiencing side effects from its administration, realize that side effects can linger after a drug has been eliminated.  The levonorgestrel can induce neurophysiologic changes and it may take your body awhile to readjust itself back to homeostasis – even though the drug is no longer in your plasma.  Should you have any further concern about Plan B staying in your system for an abnormally long duration, consult a medical professional.

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{ 4 comments… add one }
  • Stephanie June 2, 2016, 12:32 pm

    It has been two weeks since I took the drug. The crimson lady came and went and I’m having side effects similar to early pregnancy but then again I usually respond badly to most synthetic hormones (bad reaction to the pill years ago). I’m having morning anxiety, lethargy, vivid dreams and experienced a little nausea yesterday.

    Same reaction I had to birth control pills years ago. I will try the charcoal though. Thanks for the tips! :) Excellent article by the way. Very informative.

  • Johanna Barclay August 16, 2016, 6:04 pm

    Ugh, I took it six weeks ago and had my period on time (was crankier than usual) but I’ve just felt terrible very since. Nausea, feeling tired and irritable. I’ve done 2 pregnancy tests and they were negative. Will try charcoal too.

  • Noshin S August 20, 2016, 10:52 am

    I took the 1.5mg version exactly a week ago, and after about a day or so after administration I started noticing I’ve been losing a bit more hair than I normally do. How long does this last for? And how long until it stops? The medicine, I assume, should clear by next week at the latest.

  • Syreeta October 16, 2016, 4:39 pm

    I took Plan B a week and a half go. 4 days after I experienced an anxiety attack and then nervousness daily there after. Two days from that anxiety attack I experienced another one along with having up and down spills of nervousness and depression. I then got my period the following day. This period was very early coming two weeks to the date after my last period and was heavier than normal.

    Now it’s 10 days later and I’m starting to feel better emotionally. I’ve been staying in nature and using EFT to deal with the anxiety. It dawned on me just today that I took this pill and it may have had some side effects. As I’ve been doing some research and I realize what side effects occur from taking the pill and I’m putting two and two together. I want to mention too that I have low magnesium and potassium and my kidneys may be overworked.

    I’m definitely gonna use the Activated Charcoal as I thought about that the other day. Seeing it on this site was pretty much a synchronicity for me. :) If you have any physical limitations like kidney failure, acute or other. I HIGHLY recommend consulting with your doctor prior to taking Plan B. I hope my experience is helpful for someone.

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