Levonorgestrel

Levonorgestrel
ATC Code G03AC03, G03AD01, G03DA06
Formula C21H28O2
Molar Mass (g·mol−1) 312,45
Physical State solid
Melting Point (°C) 240
PKS Value 17.91
CAS Number 797-63-7
PUB Number 13109
Drugbank ID DB00367
Solubility poorly soluble in water, very soluble in dichloromethane and ethanol

Basics

Levonorgestrel is a synthetic progestin that is similar to progesterone and is used for contraception and hormone therapy. It can also be used in emergency contraception. It is usually given in tablet form, but can also be given in the form of an injection or hormonal coil. Levonorgestrel is available only on prescription.

Pharmacology

Pharmacodynamics

Oral contraceptives containing levonorgestrel suppress gonadotropins, thereby inhibiting ovulation. Specifically, levonorgestrel binds to progesterone and androgen receptors and slows the release of gonadotropin-releasing hormone (GnRH) from the hypothalamus. This process results in suppression of the normal physiological rise in luteinizing hormone (LH) that precedes ovulation. It inhibits the rupture of follicles and the release of viable eggs from the ovaries. Levonorgestrel has been shown to be more effective when administered prior to ovulation.

Pharmacokinetics

Orally administered levonorgestrel is absorbed in the gastrointestinal tract, whereas levonorgestrel administered via a hormonal IUD is absorbed in the endometrium. Protein binding of levonorgestrel ranges from 97.5-99%. The liver enzymes CYP3A4 and CYP3A5 are mainly involved in metabolism. Approximately 45% of the oral dose and its metabolites are excreted in the urine. Approximately 32% of the oral dose is excreted in the feces.

Drug interactions

When taken concomitantly with drugs that induce the liver enzyme CYP3A4, levonorgestrel may be metabolized more rapidly and may be less effective. These include, but are not limited to, barbiturates, bosentan, carbamazepine, felbamate, griseofulvin, oxcarbazepine, phenytoin, rifampin, St. John's wort, and topiramate.

Toxicity

Side effects

In clinical trials, the following side effects occurred very frequently:

  • Hives
  • dizziness
  • hair loss
  • headache
  • Nausea
  • abdominal pain
  • Uterine pain
  • delayed menstruation
  • heavy menstruation
  • uterine bleeding
  • Fatigue

Other possible side effects:

  • Diarrhea
  • vomiting
  • painful menstruation

Toxicological data

LD50 (rat, oral): >5000 mg/kg

Sources

  • Drugbank
  • PubChem
  • Aktories, Förstermann, Hofmann, Starke: Allgemeine und spezielle Pharmakologie und Toxikologie, Elsvier, 2017
Markus Falkenstätter

Markus Falkenstätter
Author

Markus Falkenstätter ist Autor zu pharmazeutischen Themen in der Medizin-Redaktion von Medikamio. Er befindet sich im letzten Semester seines Pharmaziestudiums an der Universität Wien und liebt das wissenschaftliche Arbeiten im Bereich der Naturwissenschaften.

Mag. pharm Stefanie Lehenauer

Mag. pharm Stefanie Lehenauer
Lector

Stefanie Lehenauer ist seit 2020 freie Autorin bei Medikamio und studierte Pharmazie an der Universität Wien. Sie arbeitet als Apothekerin in Wien und ihre Leidenschaft sind pflanzliche Arzneimittel und deren Wirkung.

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