Jun 09 2011

Antibiotics and Birth Control

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There are a lot of confusion, worry and stress about the usage of antibiotics and birth control hormones. A lot of  women find out that antibiotics can affect the effectiveness of birth control hormones after starting to take it. This is also another reason to be honest with your doctor and pharmacist when they ask what medicines you are using.


For example:

“I am on the pill and I took a large dose of antibiotics to have a dental procedure; it was a one-time dose. Do I need to be concerned about the increased chance of getting pregnant on BC taking antibiotics, how long will these effects last? Meaning how soon can I have worry-free sex again?”

“I have been on the pill for about 5 years now, and I take it regularly. I just got on antibiotics for an ear infection. I forgot that antibiotics can mess up the birth control. I let my boyfriend ejaculate inside me. Is there a chance I am pregnant? I am scared. Please help.”

“I’ve been on a low dose birth control for about 5-6 months. I started Augmentin for an ear infection on Monday. On Wednesday I had unprotected sex with my partner, and my partner ejaculated inside of me. What are my chances of being pregnant?”

“I’m 19 and I am scared. Me and my boyfriend had unprotected sex on Oct. 18. I am on birth control pills and I take them faithfully every day. I am almost positive he did not ejaculate in me, but I do not know for sure. What do you think I should do?”

“My partner ejaculated inside me the day before I started the inactive pills. Two days later my doctor gave me antibiotics for a UTI. I had unprotected sex every day for the next week. I started the next pack of birth control pills at the right time. Am I safe?”

It is however also true that some doctors do not accurately reflect the risk to their patients. They will just say that all antibiotics affect the protection from birth control hormones. That way they are covered from malpractice if you do get pregnant and you think it can be the medicines they prescribed that allowed that to happen. This is not true. It is not a mystery why antibiotics affect birth control hormones, so it is not a mystery which ones does do that.

Why does antibiotics affect birth control efficacy?

Birth control makes you infertile by manipulating your body’s hormones. Anything that can interfere with the hormones, the hormone actions or how your body deals with the hormones, can affect the protection provided by the birth control hormones. Hormonal birth control (pills, ring, patch, implant, injection) contains estrogen. Some antibiotics, cause the enzymes in the liver to increase the break-down of estrogens, and thereby decrease the levels of estrogens in the body and thus, the effectiveness of the pills. This can result in unwanted pregnancy.

A second way that antibiotics could interfere with the effectiveness of birth control pills is by reducing the re-circulation of estrogens within the body. Estrogens (for example, ethinyl estradiol) in birth control pills are broken-down by conversion in the liver to other chemicals which are then secreted into the intestines. Bacteria in the intestine are able to convert these chemicals back into the active estrogen which is then reabsorbed into the body. This re-circulation is called entero-hepatic cycling. Theoretically, antibiotics can kill the bacteria that convert the inactive chemicals to the active estrogen, and, therefore, may interfere with the effectiveness of birth control pills.

There are no studies that could difinitively prove or disprove these theories about birth control and antibiotics. It is however better to be cautious. Abstain from sex or use condoms while taking antibiotics that are known to interfere with birth control hormones. As a safety precaution, abstain or use condoms while you are taking any antibiotics and keep on doing so until 7 days after the last dose of antibiotics.

 Here is a summarized list of known issues:

 Antibiotics that definitely affect the efficacy of your birth control

  •  Rifampin – Brand name Rifadin, Rimactane, IsonaRif, Rifamate, Rifater

Prescribed for TB, normally for months or years at a time

  •  Griseofulvin – Brand names: Fulvicin P/G, Fulvicin-U-F, Grifulvin V, Gris-PEG, Grisactin, Grisactin Ultra, Griseofulicin

Used to treat skin infections such as jock itch, athlete’s foot, ringworm, fungal infections of the scalp, fingernails, and toenails.


 Antibiotics that may affect your birth control efficacy:

  •  Amoxicillin – Brand name Amoxil, Amoxicot, Dispermox, Moxatag, Moxilin, Senox, Sumox, Trimox, Wymox, Amoclan, Augmentin

Used to treat Ulcers, chronic astritis, Pneumonia, Bronchitis, Flu, Gonorrhea

  •  Ampicillin – Brand name Amficot, Marcillin, Omnipen, Polycillin, Principen, Totacillin

Used to treat infections caused by bacteria such as pneumonia, bronchitis,  ear, lung, skin, and urinary tract infections

  • Metronidazole – Brand name Flagyl, Metryl, Protostat

Used to treat bacteria and other microorganisms that cause infections of the reproductive system, gastrointestinal tract, skin, vagina, and other areas of the body.

  •  Minocycline – Brand name Cleeravue-M, Dynacin, Minocin, Myrac, Solodyn, Vectrin

Used to treat bacterial infections including pneumonia, other respiratory tract infections, acne, infections of skin, genital, and urinary systems. It can also be used to eliminate bacteria from your nose and throat that may cause meningitis

  •  Nitrofurantoin – Brand name Furadantin, Macrobid, Macrodantin, Nitro Macro

Used to treat urinary tract infections.

  •  Penicillin – brand name Beepen-VK, PC Pen VK, Pen-Vee K, Truxcillin-VK, V-Cil-K, Veetids

Used to treat certain infections caused by bacteria such as pneumonia, scarlet fever, and ear, skin, and throat infections. It also is used to prevent recurrent rheumatic fever and chorea.

  • Sulfamethoxazole/Trimethoprim – Brand names: Proloprim, Trimpex, Bacter-Aid, Bactrim, Cofatrim Fort, Cotrim, Cotrim DS, Septra, Sulfatrim, Uroplus

Used to eliminate bacteria that cause urinary tract infections, in combination with other drugs to treat certain types of pneumonia. Also is used to treat ‘travelers’ diarrhea.

  •  Tetracycline – brand name Sumycin

Used to treat bacterial infections, pneumonia and other respiratory tract infections, acne, infections of skin, genital and urinary systems, infection that causes stomach ulcers (Helicobacter pylori), Lyme disease, treatment and prevention of anthrax, preventing the growth and spread of bacteria



DrugStore.com,  ask your pharmacist – Do antibiotics interact with birth control pills?  http://www.drugstore.com/ask/do-antibiotics-interact-with-birth-control-pills/qxa1091

MedicineNet.com, Doctor’s Responses – http://www.medicinenet.com/script/main/art.asp?articlekey=17192

PubMed Health, Drugs and Supplements – http://www.ncbi.nlm.nih.gov/pubmedhealth/s/drugs_and_supplements/a/

The Best of Dr Oz – Do Antibiotics Interfere with the Pill? – http://www.oprah.com/health/How-Antibiotics-Affect-Birth-Control-Pills

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