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Progestin-only Pills
Unlike
combined pills, Progestin Only Pills (POP) contain only progestogens or progestins
and do not have other synthetic hormone, oestrogen. POP is also called as "mini-pill".
How Progestin-only Pills work?
It works in three ways to prevent
pregnancy:
1. It stops ovary to release eggs so that it can not meet with sperm
for fertilization.
2. It thickens the wall of uterus thus becoming impossible
to get pregnancy.
3. It also thickens the cervical mucus between vagina and
uterus so it makes very difficult for sperm to pass through vagina to reach the
egg.
Types of Progestin-only Pills :
POP can be generally classified
into three types of doses - very low, intermediate and high
Very low dose
POP contraceptives inconsistently slow down ovulation in most cases of ~50% of
cycles. It thickens the cervical mucus to stop sperm penetration. Examples of
low-dose POP are subdermal implants Norplant and jadelle, IUD (intrauterine system)
and Mirena.
Intermediate dose progestin-only pills do allow follicular development
to some extent but still consistently slow down the ovulation in 97-99% of cycles.
It also thickens the cervical mucus like very-low dose POPs do to stop penetration
of sperm. This type of POP is available in Cerazette (or the subdermal implant,
Implanon)
High dose progestine-only
pills completely stops ovulation i.e release of eggs. Similarly, it als thickens
the cervical mucus to stop sperm penetration. High dose POP is found in Depo-Provera
and Nristerat.
Effectiveness of Progestin-Only Pill:
POPs are very
much effective in preventing unwanted pregnancy upto 99% if taken as directed.
POP must be taken very strictly on time i.e within 3 hours vs combined contraceptive
pills. However, intermediate dose pop like Cerazette may require approval for
upto 12 hours in some countries. Failure rates may vary as per user's compliance
with the instruction and drug-drug interaction including anti-biotics.
It
is not confirmed to what extent POPs are safe against endometrial and ovarian
cancer compared to combined birth control pills. Similarly, there is no evidence
that breast cancer would increase due to POP use, however, due to lack of evidence,
there could be chances of "possible carcinogenic".
Available Progestin-only
pills:
| Generic Name | Brand Name |
| norgestrel | Ovrette |
| norethindrone | Micronor, Nor-QD |
Please also read how
to choose the right birth control pills to know the advantages and disadvantages
of POP pill in details.
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Contraceptive Pill
