ORAL CONTRACEPTIVE
Drugs are available that decrease fertility by a number of
different mechanisms, such as preventing ovulation, impairing gametogenesis or
gamete maturation, and interfering with gestation. Currently, interference with
ovulation is the most common pharmacologic intervention for preventing pregnancy.
Contraceptive means interception in
the birth process at any stage ranging from ovulation to ovum implantation. An
ideal contraceptive agent should not only be safe but provide reversible
suppression of fertility.
Oral Contraceptive
(I) COMBINATION PILLS: containing a
combination of Estrogen + Progestin in varying amounts or in phased regimens
(Monophasic, Biphasic or Triphasic).
(ii) MINI PILLS (Progestin only
pills)
(iii) POST COITAL (Morning after)
Pills.
(iv) CENTCHROMAN: Non-Hormonal
estrogen receptor antagonist.
1. Combination oral contraceptives:
Products containing a combination of an estrogen and a
progestin are the most common type of oral contraceptives.
Monophasic combination pills
Monophasic combination pills contain a constant dose of
estrogen and progestin given over 21 days.
ESTROGEN PROGESTERONE
1.Ethinyl Estradiol (30μg) + Norgestral (300μg)
2.Ethinyl Estradiol (30μg) +Levonorgestral(150μg)
3.Ethinyl Estradiol (50μg) + Norgestral (0.5mg)
4.Mestranol Estradiol(50μg) + Norethindrone(1mg)
5.Ethinyl Estradiol (30μg) + Desogestral (150μg)
These are called Monophasic combination pills. No Phasic
↑or↓ In the E/P content during 21 days of pill administration. The First pill
is taken on the 5th day after starting of the menses. One Pill is to be taken
each day consecutively for 21 days. Next 7 days are pill free period. Next
course starts after the 5th day of menstruation. A regular cyclic menstrual bleeding
on withdrawal of the pill (Progestogenic effect). If woman misses one pill some
day she should take 2 pills next day & continue the pill as used. Pills
that have been missed for 2-3days or at frequent days, the course should be stopped. Mechanical barriers like Condoms,
Diaphragm or Jelly should be used & next course start from 5thday of menses
as usual.
Biphasic combination pills
Biphasic & Triphasic pills Mimic the hormonal changes
during the menstrual cycle.
Biphasic pills have a fixed dose of estrogen for 21days with
↑doses of progesterone during two successive phases i.e., from the day 1-10
& 11-21. Next 7days are pill free.
For Ex:
Ethinyl Estradiol(35μg) + Northindrone(0.5mg)
A pack of ten tablets from day1 to day10.
Then,
Ethinyl Estradiol(35μg) + Northindrone(1mg)
A pack of 11 tablets from day 11 – 21day.
Triphasic combination pills
Triphasic pills →Higher dose of Estrogen at near mid cycle
but ↑doses of Progesterone for three
successive phases. i.e., for 1-6, 7-11 & 12- 21days.
By a gap of 7days of pill free period.
Example:
Ethinyl Estradiol 30μg + Norgestrel 0.05mg
(6Tab→day 1-6)
Ethinyl Estradiol 40μg + Norgestrel 0.07mg
(5Tabs→day 7-11)
Ethinyl Estradiol 30μg + Norgestrel 0.125mg
(10Tabs→day 12-21)
2. Progestin-only pills:
Products containing a progestin only, usually norethindrone (called a “mini-pill”), are taken
daily on a continuous schedule. Progestin-only pills deliver a low, continuous
dosage of drug. These preparations are less effective than the combination
pill, and they may produce irregular menstrual
cycles more frequently than the combination product. The
progestin only pill has limited patient acceptance because of anxiety over the
increased possibility of pregnancy and the frequent occurrence of menstrual
irregularities. The progestin-only pill may be used for patients who are
breastfeeding (unlike estrogen, progestins do not have an effect on milk
production), are intolerant to estrogen, are smokers, or have other
contraindications to estrogen-containing products.
3. Postcoital contraception (‘MORNING AFTER PILL’):
Postcoital or emergency contraception reduces the
probability of pregnancy to between 0.2 and 3 percent. Emergency contraception uses
high doses of progestin (for example, 0.75 mg of levonorgestrel) or high doses of estrogen (100 μg
of ethinyl estradiol) plus progestin (0.5 mg of levonorgestrel) administered within 72 hours of
unprotected intercourse (the “morning-after pill”). For these regimens, a
second dose of emergency contraception should be taken 12 hours after the first
dose. A newer progestin-only regimen consists of a one-time dose of 1.5 mg levonorgestrel. For maximum effectiveness,
emergency contraception should be taken as soon as possible after unprotected
intercourse and preferably within 72 hours. The progestin-only emergency
contraceptive regimens are generally better tolerated than the
estrogen-progestin combination regimens. A single dose of mifepristone has also been used for emergency contraception.
4. CENTCHROMAN
It is a non steroidal antagonist And available as Tab
containing 30mg of Centchroman in each Tab.
·
Centchroman
→taken twice in a week for first 3 months & then once a week subsequently
to be continued irrespective of the following menstrual cycles, as long as
contraception is desired.
·
The
1st Tab →should be taken on the first day of menstrual cycle (Eg. Sunday)
·
2nd
Tab → on 4th day of the cycle (i.e.,Wednesday)
·
Subsequent
Tab →taken on every sun & wed for 1st 3 months.
·
Followed
by once a week on the same day every week.
·
The
missed Tab →taken as soon as possible & the normal schedule should be
adhered to.
If the dose is missed by 2-7days, the normal dose schedule
is maintained. But mechanical barrier contraception (Eg .condoms) are used as
preventive measure additionally. Till the next menstrual period. If the dose is
missed for more than 7days, reinitiate by weekly schedule for 3months &
weekly schedule there-after. Centchroman is a potent competitive antagonist at
peripheral estrogen receptors & suppress proliferative stage of
endometrium.
Mechanism of action
Hormonal birth control medications
prevent pregnancy through the following ways:
Ø By blocking ovulation (release of an
egg from the ovaries), thus preventing pregnancy
Ø By altering mucus in the cervix,
which makes it hard for sperm to travel further
Ø By changing the endometrium (lining
of the uterus) so that it cannot support a fertilized egg
Ø By altering the fallopian tubes (the
tubes through which eggs move from the ovaries to the uterus) so that they
cannot effectively move eggs toward the uterus
Adverse effects
Most adverse effects are believed to be due to the estrogen
component, but cardiovascular effects reflect the action of both estrogen and progestin.
The incidence of adverse effects with oral contraceptives is relatively low and
is determined by the specific compounds and combinations used.
1. Major adverse effects: The major adverse effects are breast fullness, depression,
fluid retention, headache, nausea, and vomiting.
2. Cardiovascular: Although rare, the most serious adverse effect of oral
contraceptives is cardiovascular disease, including thromboembolism, thrombophlebitis,
hypertension, increased incidence of myocardial infarction, and cerebral and
coronary thrombosis. These adverse effects are most common among women who
smoke and who are older than age 35 years, although they may affect women of
any age.
3. Carcinogenicity: Oral contraceptives have been shown to decrease the
incidence of endometrial and ovarian cancer. The incidence of cervical cancer
may be increased with oral contraceptives, because women are less likely to use
additional barrier methods of contraception that reduce exposure to human
papilloma virus (the primary risk factor for cervical cancer). The ability of
oral contraceptives to induce other neoplasms is controversial. The production
of benign tumors of the liver that may rupture, and hemorrhage is rare.
4. Metabolic: Abnormal glucose tolerance (similar to the changes seen in
pregnancy) is sometimes associated with oral contraceptives.Weight gain is
common in women who are taking the nortestosterone derivatives. Weight gain may be less with oral
contraceptives containing drospirenone.
5. Serum lipids: The combination pill causes a change in the serum lipoprotein
profile: Estrogen causes an increase in HDL and a decrease in LDL (a desirable
occurrence), whereas progestins may negate some of the beneficial effects of
estrogen. Therefore, estrogen- dominant preparations are best for individuals
with elevated serum cholesterol.
Contraindications:
Oral contraceptives are
contraindicated in the presence of cerebrovascular and thromboembolic disease,
estrogen dependent neoplasms, liver disease, and pregnancy. Combination oral
contraceptives should not be used in patients over the age of 35 who are heavy
smokers.
Drug Interaction:
v The effectiveness of COC, POP and
EHC will be reduced by interaction with drugs that are enzyme inducers
v Broad spectrum antibiotics may
reduce effectiveness of COC by altering the bacterial flora of the bowel.
v Certain drugs can decrease the
effectiveness of combination-type birth control pills by decreasing the drug
concentration in your system (impaired enterohepatic recirculation or hepatic
induction). This can result in pregnancy.
v Drugs that may cause this effect include:
many antibiotics (e.g., cephalosporins, chloramphenicol, macrolides, penicillins,
tetracyclines, sulfas), aprepitant, bexarotene, bosentan, dapsone,
griseofulvin, certain HIV protease inhibitors (e.g., amprenavir, nelfinavir,
ritonavir), modafinil, nevirapine, rifamycins (e.g., rifampin), many seizure
medications (e.g., barbiturates, carbamazepine, phenytoin, primidone,
topiramate), St. John's wort.
v Before using this medication, tell
your doctor or pharmacist of all prescription and non-prescription/herbal
medications you may use, especially of: thyroid hormone drugs, certain
benzodiazepines (e.g., diazepam, chlordiazepoxide), prednisone-like drugs,
certain antidepressants (e.g., tricyclics), beta-blockers (e.g., metoprolol),
"blood thinners" (anticoagulants such as warfarin), insulin.
v This product can affect the results
of certain lab tests (e.g., thyroid). Inform all laboratory personnel that you
use this drug.
v Birth control pills may
significantly intensify the effects of alcohol.
v Consult your doctor or pharmacist
about this. Do not start or stop any medicine without doctor or pharmacist
approval.