Levonorgestrel

Benjamin Clanner-Engelshofen is a freelance writer in the medical department. He studied biochemistry and pharmacy in Munich and Cambridge / Boston (USA) and noticed early on that he particularly enjoyed the interface between medicine and science. That is why he went on to study human medicine.

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The active ingredient levonorgestrel is an artificially produced corpus luteum hormone (progestin) which, depending on the dosage, is used as a contraceptive pill or as a so-called “morning-after pill”. It is mostly taken in tablet form. A “coil” with levonorgestrel is also available as a mechanical contraceptive. Read more about levonorgestrel, morning-after pill and contraceptive pill here.

This is how levonorgestrel works

The active ingredient levonorgestrel influences the body's own regulation of the menstrual cycle. This can be roughly divided into two sections, each lasting around two weeks: the follicle and the luteal phase.

The follicular phase begins on the first day of your menstrual period (menstruation). The layer of mucous membrane in the uterus that was built up in the previous cycle is now expelled along with the unfertilized egg cell. At the same time, a new ovarian follicle with an egg cell inside matures in one of the ovaries (sometimes in both).

Ovulation heralds the second half of the cycle, the luteal phase: the ovary or the ovarian follicle releases the egg cell and the fallopian tube picks it up. It is now capable of fertilization for about 12 to 24 hours. The now empty follicle in the ovary changes into the corpus luteum and begins to produce the corpus luteum hormone progesterone. It suppresses the maturation of further follicles in the ovaries and prepares the uterine lining for the possible implantation of the fertilized egg cell. Later, the placenta takes over the production of progesterone and thus ensures that the pregnancy is maintained.

If, on the other hand, fertilization does not take place, the corpus luteum shrinks, which means that no more progesterone is formed. With the next menstrual period, the thickened uterine lining is shed and excreted together with the non-fertilized egg cell.

Levonorgestrel simulates pregnancy

By taking a synthetic progesterone analog such as levonorgestrel, the body is simulated pregnancy and the pituitary gland, which controls the female cycle, signals that no further ovulation or new menstrual bleeding should be initiated. Levonorgestrel also makes the secretion of the cervix tougher, which means that sperm cannot easily get into the uterus.

Natural progesterone could not be used for these purposes because it would be rapidly broken down in the liver after ingestion.

For contraception, levonorgestrel is taken alone or in combination with other hormones, adapted to the cycle, in phases or permanently.

Levonorgestrel as the morning-after pill

Levonorgestrel is also approved as the morning-after pill, which can drastically reduce the chance of pregnancy for up to three days after unprotected sexual intercourse. The exact mode of action here is not known. However, it is assumed that levonorgestrel prevents the possibly fertilized egg from implanting, prevents ovulation or hinders the transport of the egg.

Uptake, breakdown and excretion of levonorgestrel

After ingestion, levonorgestrel is completely absorbed in the intestine and reaches the highest levels in the blood after three hours. If the active ingredient is only taken once (as with the morning-after pill), half of the active ingredient is excreted after about two days. When taken repeatedly (as a contraceptive pill), the active ingredient accumulates in the body and elimination is delayed.

Levonorgestrel is broken down in the liver and about half excreted in the urine and half in the stool.

When is levonorgestrel used?

The active ingredient levonorgestrel is approved for contraception as a single active ingredient (as a so-called "minipill") or in combination with an estrogen.

The progestogen levonorgestrel is used as the morning-after pill in very high doses for emergency contraception for up to three days (72 hours) after unprotected sexual intercourse.

This is how levonorgestrel is used

A combined pill with levonorgestrel and an estrogen is usually used for contraception. It is taken for the first 21 days of the cycle (start: 1st day of the menstrual period), preferably at the same time each day. This is followed by a seven-day break before taking a new pack of pills again. With some preparations, in addition to the 21 hormone-containing tablets, a pack also contains seven placebo tablets free of active substances, so that you do not lose the rhythm of daily intake.

The minipill, which only contains levonorgestrel, is taken continuously. With her you have to pay more attention to a regular intake time. If you forget to take a pill for more than three hours, contraceptive protection is no longer guaranteed for at least seven days. The forgotten tablet of levonorgestrel should then be taken as soon as possible, even if that means that two tablets have to be taken at the same time because the time for the next dose has already been reached. Caution: This only applies in exceptional cases to the mini pill - with other contraceptive pills, two tablets must never be taken at the same time.

An intrauterine device (“coil”) with levonorgestrel works essentially like the mini pill and can remain in the uterus for up to five years.

Levonorgestrel must be taken as an emergency contraceptive (morning-after pill) as soon as possible after unprotected sexual intercourse, but no later than 72 hours. After consultation with the doctor or in the pharmacy, the tablet is taken on site, which is also to prevent the tablet from being bought “in advance”. If vomiting occurs within three hours of ingestion, a morning-after pill has to be taken to ensure that it works.

What side effects does levonorgestrel have?

Since the side effects of levonorgestrel are dose-dependent, they occur more frequently in higher doses, most notably with the morning-after pill.

Levonorgestrel side effects such as headache, nausea, pain in the lower abdomen, vaginal bleeding and fatigue occur in over ten percent of the women treated.

In addition, dizziness, diarrhea, vomiting, late menstrual bleeding, intermenstrual bleeding and a feeling of tightness in the chest can occur when a high-dose pill containing levonorgestrel is taken.

The side effects of taking as a contraceptive pill are usually less frequent and less pronounced.

What should be considered when taking levonorgestrel?

The combination with other active substances that are broken down by the same liver enzyme system (cytochrome P450 3A4) can cause levonorgestrel to be broken down more quickly and therefore not work or not work sufficiently. Examples of such active ingredients are agents against epilepsy and seizures (phenobarbital, phenytoin, carbamazepine, topiramate), agents against infections (rifampicin, efavirenz, ritonavir, griseofulvin) and the herbal antidepressant St. John's wort.

The use of levonorgestrel can increase the risk of heart attacks and strokes in patients with coagulation disorders and in smokers.

Pregnant and breastfeeding women should not take hormone preparations such as the pill (levonorgestrel alone or together with an estrogen) or the morning-after pill. The same applies to men, children, adolescents before menarche (first menstrual period) and women after menopause.

How to get levonorgestrel medication

Since mid-March 2015, the morning-after pill with levonorgestrel has been free of prescription in Germany, as in many other European countries, and can be purchased without a prescription at the pharmacy after thorough consultation.

The contraceptive pill containing levonorgestrel requires a prescription. The cost of the preparation is covered by the statutory health insurance for girls and women up to the age of 20 (women over 18 must, however, pay the prescription fee).

Since when is levonorgestrel known?

The first artificially produced gestagen used for contraception, norethisterone, was developed by the Austrian chemist Carl Djerassi in the early 1950s. The active ingredient was later developed into levonorgestrel. The contraceptive is not patent-protected, which is why numerous pharmaceutical companies sell preparations containing the active ingredient levonorgestrel.

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