mestranol/norethindrone (Necon 1/50, Norinyl 1+50)
Classes: Estrogens/Progestins; Contraceptives, Oral
Dosing and uses of Necon 1/50, Norinyl 1+50 (mestranol-norethindrone)
Adult dosage forms and strengths
mestranol/norethindrone
tablet
- 50mcg/1mg
Oral Contraceptive
1 hormonally active tablet qDay for 21 days, THEN 1 inert tablet (or tablet-free) for 7 days, repeat cycle
Follow manufacturer's color-coding (active vs inert)
Start on Day 1 of menstrual cycle or Sunday following start of menses
Initiating after Pregnancy
Increased risk for venous thromboembolism following delivery with combined hormonal contraceptives; risk declines rapidly after 21 days, but does not return to normal until 42 days after delivery
CDC guidelines recommend waiting 3-6 weeks in postpartum women without additional VTE risks (MMWR July 7, 2011)
Initiating after vaginal birth: Wait at least 3 weeks
Initiating after caesarean section birth: Wait at least 6 weeks
Women with other risk factors for VTE in addition to postpartum: Do not use combined hormonal contraceptives
Renal Impairment
Use caution; monitor blood presssure
Hepatic Impairment
Do not administer
Pediatric dosage forms and strengths
Safety and efficacy not established
Necon 1/50, Norinyl 1+50 (mestranol-norethindrone) adverse (side) effects
Frequency not defined
Common
- Emotional lability
- Headache
- Breast symptoms
- Menstrual cramps
- Abdominal pains
- Nausea
Serious
- Arterial/venous thromboembolism
- Hypertension
- MI
- Cerebral hemorrhage
- Gallbladder disease
- Hepatic adenoma
Warnings
Black box warnings
Cigarette smoking & risk of cardiovascular disease
- Cigarette smoking increases risk of serious cardiovascular adverse effects from combination hormonal contraceptive use
- This risk increases w/ age (>35 yr) & with heavy smoking (15 or more cigarettes/day)
- Advise women who use hormonal oral contraceptives not to smoke
Contraindications
Documented hypersensitivity
Active or history of breast cancer
Arterial thromboembolic disease (stroke, MI), thrombophlebitis, DVT/PE, thrombogenic valvular disease
Estrogen-dependent neoplasia
Liver disease, liver tumors
Undiagnosed abnormal vaginal bleeding
Uncontrolled hypertension
Diabetes mellitus with vascular involvement
Jaundice with prior oral contraceptive use
Precautions
Family history of breast cancer and or DVT/PE, current/history of depression, endometriosis, DM, HTN, bone mineral density changes, renal/hepatic impairment, bone metabolic disease, SLE; conditions exacerbated by fluid retention (eg, migraine, asthma, epilepsy)
Discontinue if the following develop jaundice, visual problems (may cause contact lens intolerance), any signs of VTE, migraine with unusual severity, significang blood pressure increase, severe depression, increased risk of thromboembolic complications after surgery
Discontinue 4 week before major surgery or prolonged immobilization
Patients on warfarin, oral anticoagulants (increase in anticoagulant dose may be warranted)
Some studies link OCP use with increased risk of breast cancer, whereas other studies have not shown a change in risk; woman's risk depends on conditions where naturally high hormone levels persist for long periods of time including early onset menstruation before age 12, late onset menopause, after age 55, first child after age 30, nulliparity
Increased risk of cervical cancer with OCP use, however HPV remains as main risk factor for this cancer; evidence suggests long-term use of OCPs, 5 or more years, may be associated with increased risk
Increased risk of liver cancer with OCP use; risk increases with longer duration of OCP use
CDC guidelines recommend waiting at least 3 weeks following vaginal birth or 6 weeks after cesarean section to decrease risk for venous thromboembolism before initiating combined hormonal contraceptives; women with additional risk factors for VTE (besides postpartum) should not use combined hormonal contraceptives (MMWR July 7, 2011)
Pregnancy and lactation
Pregnancy category: X
Lactation: small amounts of steroids are excreted in breast milk; estrogens may reduce quality/quantity of milk; may be prudent to use other forms of birth control until full weaning (AAP Committee states compatible w/ nursing)
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Necon 1/50, Norinyl 1+50 (mestranol-norethindrone)
Mechanism of action
Mestranol: Estrogen; reduces LHRH release from hypothalamus, reduces gonadotropin release from pituitary; increases synthesis of DNA, RNA, and various proteins in target tissues
Norethindrone: Progestin; inhibits secretion of gonadotropins from pituitary; prevents follicular maturation and ovulation, stimulates growth of mammary tissues
Absorption
Bioavailability: 60% (norethindrone)
Peak plasma time: 8 hr (ethinyl estradiol [active metabolite]); 1-2 hr (norethindrone)
Distribution
Protein bound: 80% (ethinyl estradiol [active metabolite]); 61% (norethindrone)
Metabolism
Mestranol: Metabolized to ethinyl estradiol via demethylation
Norethindrone: Liver
Metabolites
- Mestranol metabolized to ethinyl estradiol; ethinyl estradiol further metabolized to estriol, estrone by liver CYP3A4
- Norethindrone: Sulfate and glucuronide metabolites (inactive)
Elimination
Half-life: 4-13 hr (norethindrone)
Excretion
- Ethinyl estradiol (active metabolite): in urine as conjugates, most estrogens are also excreted in the bile and undergo enterohepatic recycling
- Norethindrone: 33-81% urine; 35-43% feces
