How Do Oral Contraceptives Work?

Oral contraceptives, also known as birth control pills, are hormonal medications taken before and/or after vaginal intercourse to prevent pregnancy. Oral contraceptives work by interfering with a woman’s natural hormonal balance that enables ovulation, egg fertilization, implantation, and maintenance of pregnancy.

Oral contraceptives are formulations of only progestin or a combination of progestin and estrogen. Oral contraceptives are synthetic forms of the natural female sex hormones progesterone and estrogen and have similar effects. Some oral contraceptives contain iron to supplement the body’s needs, in case of insufficiency.

Oral contraceptives bind to progesterone and estrogen receptors, protein molecules in cells that respond to these hormones, and disrupt the hormonal balance to prevent pregnancy. Oral contraceptives work in the following ways:

• Suppress ovulation and maturation of the ovum by reducing the release of hormones such as luteinizing-hormone releasing hormone (LHRH) from the hypothalamus, and the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the pituitary gland.
• Thicken the cervical mucus, hindering the passage of sperm into the uterus.
• Thin the uterus lining (endometrium) preventing implantation of the fertilized egg.

Oral contraceptives are tablets of varying formulations of progestin-only or progestin/estrogen combination, taken one a day at the same time every day, starting on the first day of menstruation. Oral contraceptives are available in packs of different cycles such as:

• 21-day cycles: Taken in 21-day cycles with seven no-pill days during which time menstruation will occur.
• 28-day cycles: Taken in 28-day cycles with hormonally active pills for 21 days and inert pills for seven days. Having no gap in ingestion makes compliance easier.
• 91-day cycles: Taken in 91-day cycles with active pills for 84 days and estrogen-only or inert pills for seven days. Menstruation occurs only once in three months.
• Yearly cycle: Continuous ingestion of low dose pills every day for a year or longer. Periods may get lighter or stop altogether during the period it is followed.

Most oral contraceptives are taken every day in cycles during the period birth control is followed. In case of unprotected vaginal intercourse or a known or suspected contraceptive failure, emergency birth control tablets can be taken. Post-intercourse tablets are taken just once and must be taken as early as possible within 72 hours after, to be effective.

Oral contraceptives may not be suitable for women over the age of 35 who smoke or have certain health conditions such as cardiovascular diseases or diabetes mellitus. The uses of oral contraceptives include:

FDA-approved:

• Contraception in females with reproductive potential
• Progestin-only emergency post-intercourse contraception 
• Treatment of moderate acne vulgaris
• Premenstrual dysphoric disorder (a severe form of premenstrual syndrome)
• Hormone replacement therapy for the treatment of moderate to severe vasomotor symptoms in menopause with an intact uterus, and prevention of osteoporosis in postmenopausal women with an intact uterus

Off-label uses:

• Dysmenorrhea (painful menstruation)
• Dysfunctional uterine bleeding
• Endometriosis (a disorder in which endometrial tissue grows outside the uterus)
• Polycystic ovarian syndrome

Side effects of oral contraceptives may include the following:

• Unscheduled bleeding
• Bleeding/menstrual irregularities
• Emotional lability (mood disturbances/swings)
• Headache, including migraines
• Premenstrual syndrome (PMS)
• Menstrual cramps
• Change in menstrual flow
• Breakthrough bleeding
• Spotting
• Amenorrhea (absence of menstruation)
• Metrorrhagia (vaginal bleeding between periods)
• Dysmenorrhea (painful menstruation)
• Scanty vaginal bleeding
• Menorrhagia (heavy and prolonged menstrual periods)
• Ovarian cysts
• Enlarged follicles
• Vulvovaginitis (inflammation of the vulva and vagina)
• Vaginal hemorrhage
• Vaginal moniliasis (Candida yeast infection)
• Leukorrhea (whitish vaginal discharge)
• Ectopic pregnancy
• Uterine leiomyoma (fibroid)
• Breast symptoms such as:
  • Enlargement or swelling
  • Tenderness
  • Pain or discomfort
  • Galactorrhea (milky secretion from the nipples)
• Acne
• Weight gain
• Pelvic pain
• Pelvic infection
• Edema
• Weakness
• Appetite changes
• Anorexia (loss of appetite)
• Abdominal pains
• Nausea
• Vomiting
• Flatulence
• Bloating
• Diarrhea
• Decrease in or loss of libido
• Increased libido, rare
• Weight loss, rare
• Insomnia
• Depression
• Anxiety
• Irritability
• Nervousness
• Dizziness
• Somnolence (drowsiness)
• Hypoesthesia (reduced skin sensation)
• Paresthesia (abnormal skin sensation)
• Hot flush
• Hypercholesterolemia (high cholesterol level in the blood)
• Hyperkalemia (high potassium in the blood)
• Venous/arterial thromboembolic (blood clot-related) events including:
  • Deep vein thrombosis/DVT (blood clot in deep veins)
  • Pulmonary embolism/PE (blood clot in the lung)
  • Stroke
  • Myocardial infarction (heart attack)
  • Intracardiac thrombosis
  • Cerebrovascular thrombosis
  • Retinal vein thrombosis
  • Thrombophlebitis (inflammation in the wall of a vein with a blood clot)
• Varicose vein aggravation
• Cerebral hemorrhage
• Optic neuritis (inflammation of the optic nerve)
• Contact lens intolerance, rare
• Hypertension (high blood pressure)
• Chest pain
• Palpitations
• Dyspnea (shortness of breath)
• Respiratory symptoms
• Nasopharyngitis (nose and throat inflammation)
• Cough
• Cholestasis (impaired bile flow from the liver)
• Cholestatic jaundice
• Gallbladder disease
• Hepatic adenoma (benign liver tumor)
• Malignant neoplasm (tumor) in liver
• Pancreatitis (inflammation of the pancreas)
• Hypersensitivity reactions such as:
  • Rash
  • Urticaria (hives)
  • Hemorrhagic eruption
  • Toxic skin eruption
  • Erythema multiforme (round lesions like a bullseye)
  • Erythema nodosum (tender bumps under the skin)
  • Chloasma/melasma (facial skin pigmentation disorder)
  • Angioedema (swelling in the tissue under the skin or mucous membranes)
• Hirsutism (inappropriate male pattern hair growth)
• Pain in extremities
• Arthralgia (joint pain)
• Back pain
• Muscle spasm

Information contained herein is not intended to cover all possible side effects, precautions, warnings, drug interactions, allergic reactions, or adverse effects. Check with your doctor or pharmacist to make sure these drugs do not cause any harm when you take them along with travel medicines. Never stop taking your medication and never change your dose or frequency without consulting your doctor.

Generic and brand names of oral contraceptive drugs include:

• Aftera
• Altavera
• Alyacen 1/35
• Alyacen 7/7/7
• Amethia
• Amethia Lo
• Amethyst
• Apri
• Aranelle
• Ashlyna
• Aubra
• Aviane
• Azurette
• Balcoltra
• Balziva 28
• Bekyree
• Beyaz
• Blisovi 24 Fe
• Blisovi Fe 1.5/30
• Blisovi Fe 1/20
• Briellyn
• Camrese
• Camrese Lo
• Caziant
• Chateal
• Cryselle
• Cyclafem 0.5/35
• Cyclafem 1/35
• Cyclafem 7/7/7
• Cyclessa
• Cyonanz
• Cyred
• Cyred EQ
• Dasetta 1/35
• Dasetta 7/7/7
• Daysee
• Delyla
• Desogen
• desogestrel/ethinyl estradiol
• dienogest/estradiol valerate
• drospirenone
• drospirenone/ethinyl estradiol
• drospirenone/ethinyl estradiol/levomefolate
• Econtra EZ
• Elifemme
• Elinest
• Emoquette
• Enpresse
• Enskyce
• Estarylla
• estetrol/drospirenone
• Estrostep Fe
• etynodiol/ethinyl estradiol
• FaLessa
• FaLessa Kit
• Fallback Solo
• Falmina
• Fayosim
• Femhrt
• Femynor
• Fyavolv
• Generess Fe
• Gianvi
• Hailey 1.5/30
• Introvale
• Isibloom
• Jevantique Lo
• Jinteli
• Jolessa
• Juleber
• Junel 1.5/30
• Junel 1/20
• Junel Fe 1.5/30
• Junel Fe 1/20
• Junel Fe 24
• Kaitlib Fe
• Kariva
• Kelnor
• Kimidess
• Kurvelo
• Larin 1.5/30
• Larin 1/20
• Larin 24 FE
• Larin FE 1.5/30
• Larin FE 1/20
• Larissia
• Layolis FE
• Leena
• Lessina 21
• Lessina 28
• Levonest
• levonorgestrel oral
• levonorgestrel oral/ethinyl estradiol
• levonorgestrel oral/ethinylestradiol/ferrous bisglycinate
• Levora
• Lillow
• Lo Loestrin Fe
• Lo Minastrin Fe
• Loestrin 1.5/30
• Loestrin 1/20
• Loestrin 24 Fe
• Loestrin Fe 1.5/30
• Loestrin Fe 1/20
• Lomedia 24 Fe
• Loryna
• LoSeasonique
• Low-Ogestrel
• Lutera
• Lybrel
• Marlissa
• Melodetta 24 FE
• Merzee
• mestranol/norethindrone (discontinued)
• Mibelas 24 FE
• Microgestin 1.5/30
• Microgestin 1/20
• Microgestin Fe 1.5/30
• Microgestin Fe 1/20
• Microgynon
• Mili
• Minastrin 24 FE
• Mircette
• Mono-Linyah
• Mononessa
• My Way
• Myzilra
• Natazia
• Necon 0.5/35
• Necon 1/50 (DSC)
• Nexesta Fe
• Next Choice One Dose
• Nextstellis
• Nordette
• Norethin 1/35E
• norethindrone acetate/ethinyl estradiol
• norethindrone acetate/ethinyl estradiol/ferrous fumarate
• norethindrone/ethinyl estradiol
• norethindrone/ethinyl estradiol/ferrous fumarate
• norgestimate/ethinyl estradiol
• norgestrel/ethinyl estradiol
• Norinyl 1+35
• Norinyl 1/50 (DSC)
• Nortrel 0.5/35
• Nortrel 1/35
• Nortrel 7/7/7
• Nylia 1/35
• Nylia 7/7/7
• Ocella
• Ogestrel
• Opcicon One-Step
• Orsythia
• Ortho Cyclen-28
• Ortho Tri-Cyclen
• Ortho Tri-Cyclen Lo
• Ortho-Cept
• Ovranette
• Philith
• Pimtrea
• Pirmella 1/35
• Pirmella 7/7/7
• Plan B One-Step
• Portia 21
• Portia 28
• Preventeza
• Previfem
• Quartette
• Quasense
• React
• Reclipsen
• Rivelsa
• Safyral
• Seasonale
• Seasonique
• Setlakin
• Slynd
• Solia
• Sprintec 28
• Sronyx
• Syeda
• Take Action
• Tarina 24 FE
• Tarina FE 1/20
• Taytulla
• Tilia Fe
• Tri-Estarylla
• Tri-Linyah
• Tri-Lo Sprintec
• Tri-Lo-Estarylla
• Tri-Lo-Marzia
• Tri-Lo-Mili
• Tri-Mili
• TriCyclen
• TriFemynor
• TriLegest Fe
• Trinessa
• TriNessa Lo
• TriPrevifem
• TriSprintec
• Trivora 28
• Tydemy
• Velivet
• Vestura
• Vienva
• Viorele
• Vyfemla
• Wera
• Wymzya FE
• Yaela
• Yasmin
• Yaz
• Zarah
• Zenchent Fe (DSC)
• Zovia