Norgestrel vs. Levonorgestrel — What's the Difference?
By Urooj Arif & Fiza Rafique — Updated on April 8, 2024
Norgestrel and levonorgestrel are both synthetic progestogens, but levonorgestrel is the active enantiomer of norgestrel, making it more potent and commonly used in contraceptives and emergency contraceptive pills.
Difference Between Norgestrel and Levonorgestrel
Table of Contents
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Key Differences
Norgestrel is a synthetic form of progesterone, a female hormone, involved in the menstrual cycle and pregnancy. Levonorgestrel, on the other hand, is the active enantiomer of norgestrel. It is more potent on a per-milligram basis because it is the form that actively binds to the progesterone receptor, exerting the desired contraceptive effects.
The distinction between norgestrel and levonorgestrel is crucial in pharmaceutical manufacturing and prescription. While norgestrel's use has declined due to the need for higher doses to achieve the desired effect, levonorgestrel's use in lower doses minimizes side effects while maintaining contraceptive efficacy.
Both norgestrel and levonorgestrel work by preventing ovulation, thickening cervical mucus to block sperm entry, and altering the uterine lining to prevent implantation of a fertilized egg. However, the preference for levonorgestrel in modern contraceptives reflects an ongoing evolution in medication to maximize effectiveness and minimize adverse effects.
In terms of medical and clinical applications, while both compounds can be used to prevent pregnancy, levonorgestrel's specificity and potency make it the preferred choice for emergency contraception. It demonstrates how advancements in pharmacology and a better understanding of drug action at the molecular level lead to more effective and patient-friendly therapeutic options.
Comparison Chart
Composition
Racemic mixture (50% active, 50% inactive enantiomer)
Active enantiomer of norgestrel
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Potency
Lower compared to levonorgestrel
More potent on a per-milligram basis
Use in Contraceptives
Used in earlier generations of birth control
Commonly used in current contraceptives
Dosage Requirement
Higher due to mixture of active and inactive forms
Lower because of its higher potency
Side Effects
Higher doses may increase the risk of side effects
Lower doses help minimize side effects
Applications
Birth control pills (less common now)
Birth control pills, emergency contraception, IUDs
Mechanism of Action
Prevents ovulation, thickens cervical mucus, alters uterine lining
Same as norgestrel, but more effectively due to higher potency
Compare with Definitions
Norgestrel
Associated with more side effects.
Higher doses of norgestrel in contraceptives could lead to more pronounced side effects.
Levonorgestrel
Preferred for its efficiency and fewer side effects.
Due to its effectiveness, levonorgestrel is favored in IUDs and birth control pills.
Norgestrel
Comprises both active and inactive forms of the hormone.
Norgestrel's effectiveness is due to its racemic mixture.
Levonorgestrel
Reflects advancements in contraceptive technology.
The development of levonorgestrel showcases progress in creating more effective and safer contraceptive options.
Norgestrel
A synthetic progestogen used in older birth control formulations.
Original contraceptive pills contained norgestrel.
Levonorgestrel
More potent and effective in lower doses.
Levonorgestrel's potency allows for its use in low-dose forms.
Norgestrel
Higher dosage requirements.
Contraceptives with norgestrel required higher doses for effectiveness.
Levonorgestrel
The active form of norgestrel used in many contraceptives.
Levonorgestrel is a key ingredient in emergency contraceptive pills.
Norgestrel
Used less frequently in modern contraceptives.
Norgestrel has been largely replaced by levonorgestrel in newer contraceptive methods.
Levonorgestrel
(pharmaceutical drug) A synthetic progestogen used as an active ingredient in some hormonal contraceptives.
Norgestrel
Norgestrel, sold under the brand name Ovral among others, is a progestin medication which is used in birth control pills and in menopausal hormone therapy. It is available both in combination with an estrogen and alone.
Levonorgestrel
Levonorgestrel is a hormonal medication which is used in a number of birth control methods. It is combined with an estrogen to make combination birth control pills.
Norgestrel
A progestin, C21H28O2, used in combination with estrogen as an oral contraceptive.
Levonorgestrel
The levorotatory form of the progestin norgestrel, used for emergency contraception, and, in combination with estrogen, in oral contraceptives and in hormone replacement therapy.
Norgestrel
(pharmaceutical drug) A synthetic progestogen C21H28O2 having two optically active forms of which the biologically active levorotatory form is used in birth control pills.
Norgestrel
Synthetic progestin used in oral contraceptives
Common Curiosities
How does levonorgestrel work?
Levonorgestrel works by preventing ovulation, thickening cervical mucus to block sperm, and altering the uterine lining to prevent egg implantation.
What is norgestrel?
Norgestrel is a synthetic progestogen used in some older contraceptive formulations, consisting of a racemic mixture of active and inactive forms.
Why is levonorgestrel preferred over norgestrel in contraceptives?
Levonorgestrel is preferred due to its higher potency, which allows for lower dosages and results in fewer side effects.
Is levonorgestrel effective as emergency contraception?
Yes, levonorgestrel is highly effective as emergency contraception, especially when taken as soon as possible after unprotected meetup.
Can norgestrel still be found in contraceptives today?
While less common, norgestrel may still be found in some contraceptive formulations, particularly in older products.
Can norgestrel and levonorgestrel be used interchangeably?
While they can both be used in contraceptive applications, levonorgestrel is generally preferred due to its efficiency and safety profile.
What advancements have been made with levonorgestrel?
Advancements include its use in lower doses for regular contraception and emergency use, minimizing side effects while maintaining efficacy.
What are the side effects of norgestrel and levonorgestrel?
Both can have side effects such as nausea, headaches, and changes in menstrual flow, but these are often more manageable with levonorgestrel due to its lower required dosage.
How are norgestrel and levonorgestrel administered?
Both are administered orally in contraceptive pills; levonorgestrel is also used in IUDs and emergency contraceptive pills.
How do healthcare providers decide between norgestrel and levonorgestrel for patients?
Decision-making is based on factors like the patient's health profile, specific needs, and the side effect profiles of each option.
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Written by
Urooj ArifUrooj is a skilled content writer at Ask Difference, known for her exceptional ability to simplify complex topics into engaging and informative content. With a passion for research and a flair for clear, concise writing, she consistently delivers articles that resonate with our diverse audience.
Co-written by
Fiza RafiqueFiza Rafique is a skilled content writer at AskDifference.com, where she meticulously refines and enhances written pieces. Drawing from her vast editorial expertise, Fiza ensures clarity, accuracy, and precision in every article. Passionate about language, she continually seeks to elevate the quality of content for readers worldwide.
