What Medications Interfere with
Birth Control Pills?
Table of Contents
Introduction
How Birth Control Pills Work
Preventing Ovulation
Thickening Cervical Mucus
Medications that Interfere
with Birth Control
Antibiotics
Antifungals
HIV Medications
Seizure Medications
St. John's Wort
Ways to Prevent
Interactions
Use Back-Up Contraception
Take Antibiotics Properly
Talk to Your Doctor
The Bottom Line
FAQs
Introduction
Birth control pills are one of
the most popular and effective contraceptive options available for women today.
Oral contraceptives like the pill, patch, and ring all contain synthetic hormones
that prevent ovulation and thicken cervical mucus to block sperm from reaching
an egg. When taken properly, birth control pills are over 99% effective at
preventing pregnancy. However, their efficacy can be impacted by certain
medications that interact with and reduce the levels of contraceptive hormones
in the body. These drug interactions can increase the risk of breakthrough
ovulation, changes in cervical secretions, and reduced birth control
effectiveness. 😳
Some of the most common
medication culprits known to interfere with birth control pills include
antibiotics, antifungals, medications for HIV and seizures, and the herbal
supplement St. John's wort. These drugs accelerate the breakdown of estrogen
and progestin, the key hormones in birth control. This allows ovulation to
start again and alters the cervical environment, making it easier for sperm to
reach an egg. Unintended pregnancies are a major concern with these medication
interactions.
In this comprehensive article, we
will take an in-depth look at how oral contraceptives work, medications that
interfere through drug interactions, ways women can prevent reduced birth
control efficacy, and the importance of being a well-informed patient. Let's
start with understanding the mechanisms of action behind the birth control
pill.👩⚕️
How Birth Control Pills Work
Birth control pills contain
synthetic estrogen and progestin hormones that alter a woman's natural
reproductive cycle in several key ways to prevent pregnancy:
Preventing Ovulation
Ovulation is the release of a
mature egg from the ovary. This normally occurs about two weeks before a
woman's period. The egg then travels down the fallopian tube to the uterus,
where it can be fertilized by sperm.
Birth control pills work by
maintaining elevated hormone levels that stop the pituitary gland in the brain
from making follicle stimulating hormone (FSH) and a surge of luteinizing
hormone (LH) that triggers ovulation. As long as the pill is taken daily, these
high contraceptive hormones signal to the ovaries that pregnancy has already
occurred; this prevents new eggs from maturing and being released each month.
Suppressing ovulation is the main way that birth control pills effectively
prevent pregnancy.
Some key points about how oral
contraceptives inhibit ovulation:
- The estrogen and progestin in
birth control stops FSH and LH from being secreted. This halts the development
of ovarian follicles that normally release mature eggs.
- No LH surge occurs to trigger
the ovaries to ovulate each month. Ovulation remains suppressed as long as the
pill is taken properly.
- Studies show the pill stops
ovulation in 97-99% of cycles when taken perfectly. This strong ovulation
suppression is key for pregnancy prevention.
- By keeping eggs from being released,
there are no eggs available to be fertilized by sperm. This is the primary
mechanism behind birth control's contraceptive effects.
- Certain medications can
increase estrogen/progestin metabolism and lower circulating hormone levels.
This impairment of ovulation suppression can reduce birth control efficacy.
In summary, birth control pills
maintain elevated hormone levels that convince the body ovulation has already
happened. This prevents new eggs from maturing and being released from the
ovaries each month. Suppressing ovulation is how oral contraceptives provide
their potent pregnancy prevention effects.
Thickening Cervical Mucus
In addition to preventing
ovulation, birth control pills also cause important changes in cervical mucus
that further help block sperm from meeting an egg.
The cervix is the narrow opening
to a woman's uterus that sits at the top of the vagina. Cervical mucus is a
fluid secretion that changes throughout the menstrual cycle and acts as a
"gatekeeper" for sperm.
Here are key effects of birth
control pills on cervical mucus:
- They cause mucus to become
thicker, denser, and more scant. This creates a barrier that prevents sperm
passage into the uterus.
- The mucus also becomes more
acidic, which impairs sperm motility and function. Fewer sperm survive when
cervical mucus is thicker.
- It produces mucus that is
sperm-hostile and difficult to penetrate. Studies show sperm take 30-40% longer
to cross mucus in women on birth control.
- Denser cervical mucus impedes
sperm capacitation - the physiological changes sperm must undergo to be able to
fertilize an egg.
- Together with suppressing
ovulation, thicker mucus provides dual birth control protection by hampering
sperm and making fertilization unlikely.
- Some medications may interfere
with these cervical changes and increase the risk of pregnancy.
In summary, the synthetic
hormones in birth control pills make cervical mucus a dense, sperm-resistant
barrier. This further enhances contraceptive effectiveness by slowing down
sperm transit and impairing sperm function when trying to reach an egg.
Now that we've reviewed how oral
contraceptives work to prevent pregnancy, let's look at the various types of medications
that can interfere with and reduce the effectiveness of birth control pills. 💊
Medications that Interfere with
Birth Control
Certain medications are known to
interact with birth control pills and lessen their contraceptive efficacy.
These drugs interfere in the following main ways:
- Increase liver enzymes that
break down estrogen and progestin faster, causing lower circulating hormone
levels
- Stimulate the liver to
metabolize birth control hormones more rapidly and clear them from the body
quicker
- Accelerate clearance of
synthetic hormones before they have maximal contraceptive effects
By quickening the metabolism of
contraceptive hormones, these interfering medications disrupt ovulation
suppression and cervical mucus changes that prevent pregnancy. Let's look
closely at the main medication culprits:
Antibiotics
Antibiotics are a class of
medications used to treat bacterial infections. Some specific antibiotics have
been shown to reduce the effectiveness of birth control pills:
- **Rifampin** - this antibiotic
used to treat tuberculosis is one of the biggest offenders for interacting with
oral contraceptives. It stimulates the liver's cytochrome P450 enzyme system,
causing faster metabolism of estrogen and progestin. This results in
contraceptive hormone levels dropping by 50% or more within days. Significant
interactions occur with rifampin.
- **Penicillins** - penicillin
antibiotics used for a variety of bacterial infections can shorten
contraceptive hormone half-lives. This was demonstrated with penicillin V and
amoxicillin decreasing birth control hormone levels.
- **Tetracyclines** - antibiotics
like doxycycline and tetracycline have been associated with reduced oral
contraceptive efficacy. These were more significant with lower dose birth
control pills.
- **Sulfonamides** - rarely
prescribed antibiotics like sulfamethoxazole can interact but typically have
minimal effect.
- **Macrolides** - erythromycin
has been implicated but interactions appear less significant. Azithromycin and
clarithromycin have displayed no interactions.
In summary, rifampin displays the
most significant interactions with birth control pills, lowering hormone levels
substantially. Penicillins and tetracyclines also have proven interactions that
can reduce contraceptive effectiveness. Being aware and using back-up methods
are key when taking these antibiotics.
Antifungals
Antifungal medications treat
fungal infections like yeast/candida, ringworm, and athlete's foot. Two main
antifungals can interact with birth control:
- **Griseofulvin** - this oral
antifungal has been shown to accelerate the metabolism of estrogens in the
liver, resulting in lowered levels and reduced birth control efficacy.
Breakthrough bleeding may also occur.
- **Ketoconazole** - very high IV
doses (not oral doses) can impact hormones but typical antifungal dosing shows
minimal interactions.
The main antifungal of concern is
griseofulvin, as it can substantially lower circulating contraceptive hormone
levels by stimulating their breakdown. Yeast medications like fluconazole have
not demonstrated interactions with birth control pills.
HIV Medications
Certain drugs used to treat HIV
and AIDS can significantly impair oral contraceptive effectiveness:
- **Ritonavir** - a protease
inhibitor used for managing HIV. It accelerates liver enzymes and can lower
hormone levels by up to 42% in just 3 days.
- **Ritonavir-boosted protease
inhibitors** - other HIV protease inhibitors like fosamprenavir, darunavir, and
tipranavir all demonstrate similarly reduced contraceptive hormone levels when
boosted with ritonavir.
- **Non-nucleoside reverse
transcriptase inhibitors (NNRTIs)** - efavirenz and nevirapine stimulate liver
enzymes and decrease contraceptive hormone concentrations substantially,
lowering efficacy.
In summary, ritonavir, other
protease inhibitors boosted with ritonavir, and NNRTIs like efavirenz impair
birth control pill effectiveness significantly by accelerating hormone
metabolism. Additional contraception should be used with these HIV drugs.
Seizure Medications
Certain anti-seizure medications
induce liver enzymes and interact with birth control pills:
- **Phenytoin** - an enzyme
inducer that can decrease estrogen levels by up to 50% with long-term use, as
well as increase breakthrough bleeding.
- **Carbamazepine** - shown to
substantially increase contraceptive hormone clearance from the body and reduce
efficacy.
- **Felbamate and Topiramate** -
these anticonvulsants may also decrease hormone levels but more modestly.
- **Barbiturates** - these older
anti-seizure meds like phenobarbital strongly induce liver enzymes and lower
hormone levels.
In summary, the main seizure
drugs to watch out for are phenytoin, carbamazepine, felbamate, topiramate, and
barbiturates. These can accelerate estrogen metabolism and impair ovulation
suppression.
St. John's Wort
This popular herbal supplement
used for treating depression demonstrates significant medication interactions
with birth control pills:
- It strongly induces liver
enzymes that break down synthetic hormones like estrogen and progestin much
more quickly.
- Studies show it can reduce
ethinyl estradiol levels in birth control by over 50% in just one week.
- The hyperforin and hypericin
components are believed to cause these interactions that lower contraceptive
efficacy.
In summary, St. John's wort is a
serious medication interacter that impairs birth control effectiveness
substantially. Avoid combining this herbal supplement with oral contraceptives.
Now that we've covered the major
medication classes that interact with birth control pills, let's discuss ways
women can prevent reduced contraceptive efficacy and unplanned pregnancies from
these interactions.
Ways to Prevent Interactions
If you need to take birth control
pills along with medications that potentially interfere, here are some
precautions you can take:
Use Back-Up Contraception
Using a secondary form of birth
control while taking any medications that interact with the pill is strongly
advised. Options for back-up contraception include:
- **Condoms** - male or female
condoms act as a physical barrier to sperm and provide good short-term back-up
protection in conjunction with an IUD, implant, shot, ring, or pills.
- **Diaphragm** - this reusable
dome-shaped cup fits inside the vagina and covers the cervix to block sperm. It
can be used with spermicidal jelly as added contraceptive protection.
- **Cervical caps** - smaller
than a diaphragm, caps fit tightly over the cervix to prevent sperm entry into
the uterus. It's also used with spermicide.
- **Spermicides** - these creams,
gels, sponges, and foams containing spermicide kill and immobilize sperm to
prevent fertilization. They can be used alone or with barrier methods.
- **Sponge** - these soft
disposable sponges are filled with spermicide and block the cervix to prevent
sperm from entering the uterus.
- **Abstinence** - refraining
from sex completely while taking interacting medications guarantees no chance
of pregnancy.
Using an added barrier method
that blocks or kills sperm along with taking birth control pills provides an
additional layer of contraceptive protection if drug interactions are a
concern.
Take Antibiotics Properly
If prescribed antibiotics that
interact with birth control pills:
- Take the antibiotics exactly as
directed by your healthcare provider.
- Never stop an antibiotic
prescription early, even if symptoms resolve. Finish the entire course of
treatment.
- Skipping pills or not
completing the antibiotics fully may lead to decreased efficacy of both the
antibiotics and birth control.
- Take the antibiotics and
contraceptive pills at least 2 hours apart to avoid any potential absorption
interference.
Taking the full antibiotic course
properly reduces the risk of birth control failure and development of
antibiotic-resistant bacteria.
Talk to Your Doctor
Being an informed, proactive
patient is key to preventing issues with medication interactions:
- Always inform your doctor and
pharmacist of ALL medications you take, including herbs and supplements. Make
sure interaction risks are discussed upfront when getting any new prescription.
- If your physician prescribes
antibiotics like rifampin that are known to cause interactions, request a
different antibiotic if possible.
- Have your clinician recommend
the best back-up method and explicitly counsel when it should be utilized to
ensure you understand proper use.
- Report any breakthrough
bleeding or spotting to your doctor, as this can be a red flag for reduced
birth control efficacy.
- Ask for regular follow-ups and
bloodwork to monitor hormonal levels after starting new medications.
- See your gynecologist quickly
if you have concerns about an unplanned pregnancy. Emergency contraception like
Plan B may be needed.
Being thorough and open with your
healthcare team ensures you get the information and care needed to prevent
pregnancy effectively if interactions are a possibility.
The Bottom Line
While most women can safely take
birth control pills along with other prescription and over-the-counter
medications, some specific drugs are known to interact and substantially reduce
oral contraceptive efficacy. The main medication offenders include rifampin,
griseofulvin, phenytoin, HIV drugs, and St. John's wort. These can increase
contraceptive hormone metabolism and clearance.
Using a back-up method of
protection like condoms or spermicide for 7-10 days after finishing the interacting
medication allows time for birth control hormone levels to increase again.
Remaining vigilant about potential interactions and being proactive by
reporting any breakthrough bleeding or concerns to your doctor is important to
avoid unintended pregnancies. If your medications are affecting your birth
control, your clinician can work with you to find the best contraceptive
solution for your situation.🙂
FAQs
Q: Do all antibiotics affect birth control pills?
A: No, the majority of
antibiotics like penicillin, cephalosporins, fluoroquinolones, macrolides, and
aminoglycosides have no effect on birth control pill efficacy. The main
antibiotic offenders are rifampin, certain penicillins, and tetracyclines,
primarily when taken long-term. Short-term antibiotic use for 10 days or less
is unlikely to impair contraceptive effectiveness.
Q: How long after taking antibiotics is birth control affected?
A: Birth control pills may be
impacted both during and for 7-10 days after stopping an antibiotic known to
interact. It's wise to use back-up contraception during the full antibiotic
course and for one week after completing the medication. This allows time for
birth control hormone levels to stabilize and ovulatory suppression to be
reestablished.
Q: Can I just take a break from the pill while on antibiotics?
A: Stopping birth control pills
suddenly while on antibiotics is not recommended, as this could lead to
unintended pregnancy. It's best to continue taking your pills according to
schedule and use additional contraception like condoms if concerned about
antibiotic interactions.
Q: What medications boost the effectiveness of birth control pills?
A: Some medications can slightly
increase circulating estrogen levels from birth control pills, including
antifungals like fluconazole, some antidepressants, anti-HIV protease
inhibitors, and antibiotics like doxycycline. However, the increase is modest
and does not make birth control pills significantly more effective.
Q: Should I take my birth control pill at the same time as other
medications?
A: It's generally best to
separate your birth control pill and other oral medications by at least 2-3
hours if possible. Consuming them at the exact same time could potentially
result in one drug impacting absorption and metabolism of the other. However,
taking them together or close in timing is unlikely to have major effects.
Q: How long do birth control interactions last after stopping a medication?
A: After discontinuing a
medication known to impair oral contraceptive effectiveness, it's recommended
to use back-up birth control like condoms for 7 days. This allows the synthetic
hormones time to reach adequate levels again to suppress ovulation and thicken
cervical mucus fully.
Q: Will my pharmacist warn me about birth control interactions?
A: Your pharmacist may note
certain medication interactions with birth control pills, but don't rely on
them catching every potential issue. Always tell your pharmacist, doctor, and
other clinicians about all drugs you take to discuss interaction risks and
precautions. Be your own best health advocate!