lynestrenol

Action and Spectrum

Actions and Spectrum: 

Mechanism of Action:  

lynestrenol exerts its effects by binding to progesterone receptors in the body. Progesterone receptors are found in various tissues, including the reproductive organs and the endometrium (uterus lining). When lynestrenol binds to these receptors, it activates them, leading to several biological effects: 

• Inhibition of ovulation: lynestrenol suppresses the release of luteinizing hormone (LH) from the pituitary gland. LH is essential for the ovarian follicle’s final maturation and the egg’s release (ovulation). By inhibiting ovulation, lynestrenol prevents eggs’ release and reduces pregnancy risk. 
• Thickening of cervical mucus: lynestrenol causes changes in the cervical mucus, making it thicker and less permeable to sperm. This makes it more difficult for sperm to enter the uterus and reach the egg, reducing the likelihood of fertilization. 
• Alteration of the endometrium: lynestrenol modifies the lining of the uterus (endometrium), making it less receptive to embryo implantation. If fertilization occurs, the altered endometrium may not support the successful implantation and growth of the embryo. 

Spectrum of Activity:  

lynestrenol is primarily used in oral contraceptives (birth control pills) and hormone replacement therapy for menopausal women. As a contraceptive, it is highly effective when used correctly, and its spectrum of activity includes: 

• Prevention of pregnancy: as part of combined oral contraceptive pills (with an estrogen component), lynestrenol effectively prevents unwanted pregnancies when directed. 
• Hormone replacement therapy: lynestrenol may also be used in hormone replacement therapy for menopausal women to alleviate menopausal symptoms and prevent endometrial hyperplasia (overgrowth of the uterine lining). 

Drug Interaction

Adverse Reaction

Frequency not defined 

Migraine 

Nervousness 

Breast tenderness and pain 

Weight increase 

Headache 

Dizziness 

Changes in libido 

Disturbances 

Black Box Warning

Black box warning: 

None 

Contraindication / Caution

Contraindications/caution: 

Contraindications: 

• Known hypersensitivity: lynestrenol should not be used in individuals with known hypersensitivity or allergy to the drug or its components.  
• History of blood clots: It is associated with a potentially increased risk of blood clot formation (venous thromboembolism). 
• Cerebrovascular disease: It is not recommended for use in individuals with a history of stroke or transient ischemic attack (TIA), as it may increase the risk of cerebrovascular events. 
• Coronary artery disease: It may be contraindicated in individuals with a history of coronary artery disease or angina pectoris, as it can potentially worsen these conditions. 
• Liver disease: It is metabolized in the liver, and its use may be contraindicated in individuals with severe liver disease or liver tumors. 
• Breast cancer or other hormone-sensitive cancers: It is a progestin, and its use may be contraindicated in individuals with a history of hormone-sensitive cancers, such as breast cancer. 

Caution: 

• Smoking: Women who smoke and use hormonal contraceptives, including lynestrenol, have a higher risk of developing severe cardiovascular events, such as blood clots, heart attacks, and strokes.  
• Age: The use of lynestrenol in adolescent girls before the onset of menstruation and in postmenopausal women is generally not indicated. 

Pregnancy / Lactation

Pregnancy consideration: It is not recommended during pregnancy 

Pregnancy Category: D (US FDA)  

Lactation: Excretion of the drug in human breast milk is unknown 

Pregnancy category: 

Category A: well-controlled and Satisfactory studies show no risk to the fetus in the first or later trimester. 

Category B: there was no evidence of risk to the fetus in animal studies, and there were not enough studies on pregnant women. 

Category C: there was evidence of risk of adverse effects in animal reproduction studies, and no adequate evidence in human studies must take care of potential risks in pregnant women.    

Category D: adequate data with sufficient evidence of human fetal risk from various platforms, but despite the potential risk, and used only in emergency cases for potential benefits.    

Category X: Drugs listed in this category outweigh the risks over benefits. Hence these categories of drugs need to be avoided by pregnant women.    

Category N: There is no data available for the drug under this category 

Pharmacology

Pharmacology: 

lynestrenol is a synthetic progestin, a synthetic version of the hormone progesterone. As a progestin, lynestrenol exerts its pharmacological effects through interaction with progesterone receptors in the body.  

• Progesterone Receptor Binding: lynestrenol binds to progesterone receptors, which are present in various tissues throughout the body, including the reproductive organs (ovaries, uterus) and the brain. Once bound to these receptors, lynestrenol activates them, leading to various biological effects. 
• Contraceptive Effect: lynestrenol is primarily used as a component of hormonal contraceptives, such as oral contraceptive pills. It exerts its contraceptive effect through several mechanisms: 
• Inhibition of Ovulation: lynestrenol suppresses the release of luteinizing hormone (LH) from the pituitary gland. LH is essential for the ovarian follicle’s final maturation and the egg’s release (ovulation). By inhibiting ovulation, lynestrenol prevents the release of eggs, reducing the risk of pregnancy. 
• Thickening of Cervical Mucus: lynestrenol causes changes in the cervical mucus, making it thicker and less permeable to sperm. This makes it more difficult for sperm to enter the uterus and reach the egg, reducing the likelihood of fertilization. 
• Modification of the Endometrium: lynestrenol alters the lining of the uterus (endometrium), making it less receptive to embryo implantation. If fertilization occurs, the altered endometrium may not support the successful implantation and growth of the embryo, contributing to the contraceptive effect. 
• Hormone Replacement Therapy (HRT): lynestrenol may also be used in hormone replacement therapy for menopausal women. In this context, it helps alleviate menopausal symptoms and prevent endometrial hyperplasia (overgrowth of the uterine lining) that can occur with unopposed estrogen therapy. 

Pharmacodynamics:  

The key pharmacodynamic effects of lynestrenol: 

• Progesterone Receptor Activation: lynestrenol binds to progesterone receptors in target tissues, including the uterus, ovaries, and brain. This activation of progesterone receptors triggers a cascade of intracellular events and molecular signaling pathways. 
• Inhibition of Ovulation: One of the primary mechanisms of action of lynestrenol as a contraceptive is its ability to suppress ovulation. By inhibiting the surge of luteinizing hormone (LH) from the pituitary gland, lynestrenol prevents the final maturation and release of the egg from the ovary, thus reducing the risk of pregnancy. 
• Changes in Cervical Mucus: lynestrenol alters the cervical mucus, making it thicker and less conducive to sperm penetration. This change in the cervical mucus prevents sperm from passing through the cervix and reaching the uterus, further contributing to the contraceptive effect. 
• Modulation of the Endometrium: lynestrenol modifies the lining of the uterus (endometrium) to create an unfavorable environment for embryo implantation. If fertilization occurs, the altered endometrium may not adequately support the implantation and growth of the embryo, reducing the likelihood of pregnancy. 

Pharmacokinetics: 

Absorption 

It is administered orally, typically in tablets or capsules. After ingestion, it is absorbed from the gastrointestinal tract into the bloodstream. The rate and extent of absorption may vary depending on individual factors, such as food intake and gastrointestinal motility. 

Distribution 

Once absorbed into the bloodstream, lynestrenol is distributed throughout the body. It binds to plasma proteins, primarily albumin, and globulins, for transport to target tissues, including the uterus, ovaries, and brain. lynestrenol’s distribution is influenced by its lipophilic nature, which allows it to penetrate cell membranes. 

Metabolism 

It undergoes extensive metabolism in the liver. The major metabolic pathway involves the reduction of the 3-keto group to form dihydrolynestrenol. The C17α hydroxyl group may also undergo oxidation to form 17α-hydroxylated metabolites. These metabolites are less potent than the parent compound but contribute to the progestational effects. 

Elimination and Excretion 

Metabolized lynestrenol and its metabolites are eliminated from the body mainly through urine and feces. The exact proportions of excretion routes may vary depending on the individual and the specific formulation of the medication. 

Adminstartion

Administration: 

Oral administration 

It is safe to take with or without meals. 

Patient Information Leaflet

Patient information leaflet 

Generic Name: lynestrenol 

Why do we use lynestrenol? 

lynestrenol is a synthetic progestin, a type of synthetic progesterone. It is primarily used in two main medical applications: 

• Contraception: lynestrenol is commonly used as a progestin component in combined oral contraceptive pills (COCs). These are birth control pills that contain both estrogen and progestin. lynestrenol, as a progestin, helps prevent pregnancy through various mechanisms, including inhibiting ovulation (the release of eggs from the ovaries), thickening cervical mucus to impede sperm entry into the uterus, and altering the endometrium (lining of the uterus) to make it less receptive to implantation of a fertilized egg. When taken correctly, COCs are highly effective in preventing unwanted pregnancies. 
• Hormone Replacement Therapy (HRT): lynestrenol is sometimes used in hormone replacement therapy for menopausal women. In HRT, it is combined with an estrogen component to provide progestational support to the endometrium. It prevents the unopposed estrogen from causing abnormal cell growth and reduces the risk of endometrial hyperplasia (overgrowth of the uterine lining). HRT with lynestrenol can help alleviate menopausal symptoms like hot flashes and night sweats.