Oral Contraceptives Pharmacology

Question 1

Oral contraceptives

Answer 1

Oral contraceptives are medications used to prevent pregnancy. They generally contain synthetic forms of hormones that regulate the menstrual cycle. Here’s a detailed look at their pharmacology:

1. Combined Oral Contraceptives (COCs)
   
   • Composition: Contain both an estrogen (usually ethinyl estradiol) and a progestin (such as levonorgestrel, norethindrone, or desogestrel).
   • Mechanism of Action:
     
     • Ovulation Inhibition: Suppress the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the pituitary gland, preventing ovulation.
     • Endometrial Changes: Thicken cervical mucus, making it difficult for sperm to enter the uterus.
     • Endometrial Lining: Alter the endometrial lining, making it less suitable for implantation.
   • Pharmacokinetics:
     
     • Absorption: Rapidly absorbed from the gastrointestinal tract.
     • Distribution: Distributed throughout the body.
     • Metabolism: Metabolized primarily in the liver.
     • Excretion: Excreted mainly in the urine.
   • Side Effects: Nausea, breast tenderness, headache, mood changes, and, rarely, thromboembolic events.
2. Progestin-Only Pills (POPs)
   
   • Composition: Contain only a progestin (e.g., norethindrone or desogestrel).
   • Mechanism of Action:
     
     • Ovulation Inhibition: May suppress ovulation, although this is not as consistent as with COCs.
     • Cervical Mucus: Thickens cervical mucus to inhibit sperm passage.
     • Endometrial Changes: Alters the endometrial lining to prevent implantation.
   • Pharmacokinetics:
     
     • Absorption: Rapidly absorbed from the gastrointestinal tract.
     • Distribution: Distributed throughout the body.
     • Metabolism: Metabolized in the liver.
     • Excretion: Excreted primarily via urine.
   • Side Effects: Irregular menstrual bleeding, headaches, and mood changes. Less risk of thromboembolic events compared to COCs.

• Effectiveness: When used correctly, oral contraceptives are highly effective in preventing pregnancy (greater than 99%). Typical use may result in a slightly lower efficacy rate due to missed doses or other factors.
• Administration: COCs are usually taken in a 28-day cycle with 21 active days of hormones and 7 days of placebo pills. POPs are taken continuously without a break.
• Drug Interactions: Some medications can reduce the effectiveness of oral contraceptives, including certain antibiotics, anticonvulsants, and herbal supplements like St. John’s Wort. Conversely, oral contraceptives can affect the metabolism of other drugs.
• Contraindications: Oral contraceptives are contraindicated in women with certain conditions, such as severe liver disease, uncontrolled hypertension, or a history of thromboembolic disorders.

• Regular Check-ups: Periodic visits with a healthcare provider are recommended to monitor for side effects and ensure the contraceptive is effective.
• Lifestyle and Health Factors: Adjustments may be needed based on individual health conditions, lifestyle, or preferences.

Oral contraceptives provide effective and convenient contraception but require careful consideration of potential side effects and interactions. Regular monitoring helps ensure their safe and effective use.