Progestin-Only Pill ("Mini-Pill")
- How does the progestin only pill work?
- How effective is the "mini-pill"?
- How is the progestin only pill (POP) usually prescribed?
- How should the progestin only pill (POP) be taken?
- How well does the progestin only pill (POP) work?
- Is a backup method of contraception required if a woman starts the progestin only pill (POP) on the first or second day of her cycle?
- Is there any lab work that should be done prior to prescribing the progestin only pill (POP)?
- What are the types of the progestin only pill (POP)?
- What pre-treatment assessment is needed prior to prescribing the progestin only pill (POP)?
- When should the progestin only pill (POP) be started?
How does the progestin only pill work?
The progestin-only pill (POP) causes endometrial suppression and thickening of cervical mucus [rendering the mucus impenetrable to sperm] for its contraceptive effect. Ovulation is inhibited in only 60 percent of women taking the POP. Because of its multiple mechanisms of action the POP, when used correctly, provides a reliable means of contraception.
How effective is the "mini-pill"?
Micronor® is a progestin-only birth control pill ("mini-pill"). Its main method of action is to thicken the cervical mucus thus preventing the passage of sperm. Other mechanisms of action include thinning the lining of the uterus (to inhibit implantation), and suppression ovulation (in only 50% of cases).
The hormonal pills must be taken every day (no pill-free interval), within a 3-hour window. The stringent rules for its use results in reported failure rates that range from 0.3% (for perfect use) to 8% (typical use). Using a backup method such as condoms will decrease the risk of unintended pregnancies.
This birth control pill is used more commonly in women with a contraindication to estrogen containing contraceptives (such as complicated migraines, smokers over 35 years of age, or previous leg /lung clots), or breastfeeding mothers.
How is the progestin only pill (POP) usually prescribed?
Pills should be prescribed for one year, with annual physical assessments, but a follow up visit in the first few months after the initial one is recommended to enhance adherence and to reinforce correct usage. This will ensure that early concerns and questions (especially about nuisance side effects) are addressed and will enhance adherence. This is particularly important for first time users and adolescents. Adolescents may require more than one follow-up in the first year to increase adherence.
How should the progestin only pill (POP) be taken?
The pills should always be taken at the same time of day (within three hours) to ensure a reliable effect. It is important to emphasize that unlike the combined oral contraceptive pill (OCP) there is no pill free interval and all twenty-eight pills in a package contain active medication.
How well does the progestin only pill (POP) work?
Progestin-only pills have a theoretic contraceptive effectiveness of 90 to 99 percent. The failure rate is lowest in highly motivated women. The effectiveness drops off dramatically with missed or delayed pill administration. The Pearl index is 0.3-4/100 women years (failure rate for 100 women using the method for one year).The higher Pearl index results when adherence is poor, particularly in very young users. The lower rate applies particularly during lactation.
Is a backup method of contraception required if a woman starts the progestin only pill (POP) on the first or second day of her cycle?
No if the POP is started on day one or day two of the menstrual cycle no additional precautions are required. If adherence in a new user is a potential problem backup contraception may be prudent initially. This back-up method is particularly important during the first month of use because first time pill users may take the pill incorrectly or forget to take the pill. Many first time users also require dual protection for sexually transmitted diseases (STD). In "at risk" individuals' condom use should be encouraged in addition to the POP to help prevent the transmission of STDs.
Is there any lab work that should be done prior to prescribing the progestin only pill (POP)?
No, routine laboratory screening is not required. Assessing the cholesterol-lipoprotein profile and carbohydrate metabolism should follow standard guidelines. A hemoglobin and platelet level may be warranted if there is a history of menorrhagia. A Von Willebrand factor may be included in the adolescent with severe menorrhagia.
What are the types of the progestin only pill (POP)?
Norethindrone 0.35mg (Micronor 28) is the only progestin-only pill marketed for contraception in Canada.
What pre-treatment assessment is needed prior to prescribing the progestin only pill (POP)?
A routine history and physical examination is advisable. The first visit is also a good time to discuss screening for and counselling about sexually transmitted disease (STD) prevention and condom use .The importance of annual pap smears as well as the benefits of smoking cessation should also be discussed. No routine blood work is required.
When should the progestin only pill (POP) be started?
The progestin-only pills should be taken from the first or second day of the menstruation cycle, and daily (nonstop) thereafter. Contraceptive reliability requires regular pill taking at the same time each day. It is important to emphasize that unlike the combined oral contraceptive pill (OCP) there is no pill free interval and that all twenty-eight pills in a package contain active medication.
