Nordette Mechanism of Action

Pharmacological class: Estrogen-progestin combination oral contraceptive (COC).
Pharmacology: Mode of action: COCs suppress gonadotropins in a manner that inhibits ovulation, which leads to contraception.
Pharmacodynamics, clinical efficacy: When taken consistently and correctly, the probable failure rate of COCs is 0.1% per year; however, the failure rate during typical use is 5% per year for all types of oral contraceptives. The efficacy of most methods of contraception depends upon the reliability with which they are used. Method failure is more likely if COC tablets are missed.
The following noncontraceptive health benefits related to the use of COCs are supported by epidemiological studies that largely utilized COC formulations containing doses exceeding 35 μg of EE or 50 μg of mestranol.
Effects on menses: Improved menstrual cycle regularity; Decreased blood loss and decreased incidence of iron-deficiency anemia; Decreased incidence of dysmenorrhea.
Effects related to inhibition of ovulation: Decreased incidence of functional ovarian cysts; Decreased incidence of ectopic pregnancies.
Other noncontraceptives health benefits: Decreased incidence of fibroadenomas and fibrocystic disease of the breast; Decreased incidence of acute pelvic inflammatory disease; Decreased incidence of endometrial cancer; Decreased incidence of ovarian cancer; Decreased severity of acne.
Pharmacokinetics: Ethinyl estradiol is subject to considerate first-pass metabolism with a mean bioavailability of 40-45%. Levonorgestrel does not undergo first-pass metabolism and is therefore completely bioavailable.
Levonorgestrel is extensively plasma protein bound both to sex hormone binding globulin (SHBG) and albumin. Ethinyl estradiol however, is bound in plasma only to albumin and enhances the binding capacity of SHBG. Following oral administration, peak plasma levels of each drug occur within 1 to 4 hours. The elimination half-life for ethinyl estradiol is approximately 25 hours. It is primarily metabolized by aromatic hydroxylation but a wide variety of hydroxylated and methylated metabolites are formed, and these are present both free and as conjugates with glucuronide and sulfate. Conjugated ethinyl estradiol is excreted in bile and subject to enterohepatic recirculation. About 40% of the drug is excreted in the urine and 60% is eliminated in the feces.
Elimination half-life for levonorgestrel is approximately 24 hours. The drug is primarily metabolized by reduction of the A ring followed by glucuronidation. About 60% of levonorgestrel is excreted in the urine and 40% is eliminated in the feces.