Plan B One-Step: Uses, Side Effects, Precautions, And More

plan b one step

What Is Plan B One-Step?

Plan B One-Step is an emergency contraceptive pill (“morning-after pill”) used to prevent unintended or unwanted pregnancy.

The active ingredient of this pill is levonorgestrel, a kind of synthetic progesterone (progestin), which inhibits ovulation, alters cervical mucus, and prevents the uterine lining from thickening.

Plan B pill is available for purchase as an over-the-counter (OTC) medicine for adult women. Minor girls or girls below the age of 17 might require a doctor’s prescription in some areas.

The original Plan B includes two contraceptive pills containing 0.75 mg of levonorgestrel each. These are to be taken either together or as two separate doses at an interval of 12 hours.

Plan B One-Step, however, consists of just one oral pill containing 1.5 mg of levonorgestrel, which is why it is aptly named One-Step. It is meant to be taken as soon as possible after unprotected sex but can be taken within a maximum of 72 hours.

A single pill is better than a two-pill combination as there is no chance of forgetting to take the second pill or of taking the pills too far apart.

Let us take a look at the uses, side effects, dosage, precautions, and drug interactions associated with Plan B One-Step.

Plan B One-Step Uses

Oral emergency contraceptives like Plan B One-Step are used to prevent pregnancy after unprotected sex or failure of other forms of birth control.

The indications for their use include:

1. Unprotected intercourse

The risk of pregnancy following a single act of unprotected coitus around the time of ovulation is approximately 8 percent.

2. Condom rupture or slippage

While condoms are the easiest form of barrier contraception and offer STD protection advantages, they are not fail-safe. Sometimes, the condom might tear or rupture during intercourse, exposing the female to the risk of getting pregnant.

3, Missed pill

Sometimes a woman might forget to take a pill and have intercourse without using any other protection. In such a case, the only option left with her is to take an emergency pill, such as Plan B One-Step.

4. Delay in taking progesterone-only pills for more than three hours

POP pills or progesterone-only pills have to be taken regularly and at the same time of the day, every day. A delay of more than three hours in taking the pill greatly amplifies the risk of unwanted pregnancy.

5. Sexual assault or rape

In case of a sexual assault, emergency contraception is the only recourse left to the victim, as pregnancy is a potential eventuality.

6. First-time intercourse, as known to be almost always unplanned

Unplanned or unexpected intercourse most often happens without any protection, thus necessitating the use of emergency contraceptive pills.

Side Effects of Plan B One-Step

Like with any other medication, there are side effects associated with Plan B One-Step Use. However, they are not long-lasting and disappear within a few days.

Side effects include:

  • Menstrual changes such as bleeding becoming heavier or lighter
  • Pain in the pelvic region
  • Nausea
  • Lower abdominal pain
  • Unusual fatigue
  • Headache
  • Feeling faint or dizzy
  • Breast pain or tenderness
  • Unexplained diarrhea
  • Vomiting

Out of these, the most commonly observed side effect is nausea. Nausea, or an urge to vomit, is experienced by one in four women taking emergency contraceptive pills.

If vomiting occurs within two hours of taking the pill, it is advisable to take a doctor’s opinion on whether you need to take another dose.

Precautions to Be Observed While Taking Plan B One-Step

The following precautions need to be observed when you take a morning-after pill:

  • Take Plan B One-Step as soon as possible or at least within 72 hours after unprotected sex.
  • Do not use this as a routine method of preventing pregnancy. It is only to be used as a backup in cases of emergency.
  • If you have ever had an unusual reaction to this medicine or other similar medicines, you should consult your health care provider before taking Plan B One-Step.
  • This pill is not recommended for use before the onset of your first-ever period (menarche). Similarly, it is not advisable to use Plan B in elderly women.
  • Plan B One-Step does not terminate an existing pregnancy and should not be used for abortions. It is only effective at preventing fertilization of an egg with sperm as it stops or delays ovulation (the release of eggs from the ovary). For this reason, it is rightly called interception.
  • Although no significant studies have been conducted to show its risks in breastfeeding women, consulting a doctor before taking the pill is advisable.
  • If you are obese, Plan B One-Step might not be as effective in the prevention of pregnancy as it is in women with normal weight. Consult your gynecologist about this.
  • This medicine may change the date of your next expected period. If, however, menses is delayed beyond one week, it is better to get a pregnancy test done and follow up with a doctor. There might also be some spotting or bleeding before the next period arrives.
  • Ectopic pregnancy should be considered when a woman complains of lower abdominal pain after taking Plan B One-Step.
  • Since one of the side effects is dizziness and fatigue, do not drive or operate heavy machinery until you know how this medicine affects you.
  • Plan B will not protect you against HIV or any other sexually transmitted diseases (STDs).

Drug Interactions of Plan B One-Step

Certain medications are contraindicated with the morning-after pill. An example of such a drug is tranexamic acid, which is used to treat heavy bleeding during a menstrual period.

Drugs or herbal products that affect the activity of some liver enzymes which cause the breakdown of drugs may reduce the effectiveness of Plan B One-Step.

These include:

  • Amoxicillin (an antibiotic used to treat various bacterial infections)
  • Barbiturates (used to treat insomnia, seizures)
  • Rifampicin (anti-tubercular drug)
  • St. John’s wort (used in depression)
  • Carbamazepine (anticonvulsant)
  • Cefixime (antibiotic)
  • Cyclosporine (immunosuppressant used in organ transplantation)
  • Dexamethasone (anti-inflammatory)
  • Phenytoin (anticonvulsant)

Some other medicines that Plan B might interact with include amitriptyline (tranquilizer), diazepam (tranquilizer), and warfarin (anticoagulant).

This is not an exhaustive list. For more information, visit Medscape Drug Interaction Checker.


Plan B One-Step is a single dose tablet containing 1.5 mg of levonorgestrel. Only one dose is sufficient to gain effective contraception.

The pill must be taken within 72 hours of unprotected sex or birth control failure. Having said that, the sooner you take it, the better it is.


Plan B One-Step is a popular morning-after pill. Taken orally, it is a safe and highly effective way of preventing unintended pregnancy. Additionally, using this pill strictly as an emergency contraceptive method will not impact your chances of getting pregnant in the future.

In this article, we have discussed the uses of the pill, the side effects that can occur with use, dosage, precautions while taking the pill, and the potential drug interactions.

Having an understanding of the above will help women be more comfortable regarding the pill’s use without worrying about either an accidental pregnancy or their health.


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