Birth Control Pill and HRT Exposure in Pets

Birth control pills and hormone replacement therapy products are commonly found in households, so it makes sense that animals would routinely find and ingest them. How concerned should you be?

Birth control pills typically contain very low doses of estrogens and progesins, and animals generally have to consume a large amount for it to be worrisome.

One exception, however, is hormone replacement therapy pills (or treatment for urinary incontinence, like DES) since those have much higher concentrations of estrogens and/or progestins.

A dose of concern for progestins is about 10 mg/kg. While life-threatening signs aren’t seen with overdoses of progestins, ataxia and lethargy may be.

Estrogens can cause severe and life-threatening signs, however; doses of 1 mg/kg and higher can cause aplastic anemia and/or bone marrow suppression and warrant monitoring a CBC for two weeks post-exposure.

Birth Control Pill Case Study 

How would you treat this hypothetical case?

Mrs. Smith calls frantically because Taffy, a 3-year-old, 45-pound Boxer mix, was caught ingesting an entire 28-day supply of birth control pills that were left out on the counter, including most of the plastic and foil.

The product is listed as a generic for Ortho Tri-Cyclen.

Fifteen minutes later, Mrs. Smith brings Taffy to your clinic. The active pills control 0.215 mg of norgestimate (a progestin) and 0.025 mg of ethinyl estradiol (estrogen), and she ingested the entire 28-day supply.

What's Taffy's dose and what should you do from here?

1. Her dose is 0.29 mg/kg of norgestimate and 0.034mg/kg of ethinyl estradiol. This is not enough to pose a significant risk, so you give her a dose of activated charcoal and send her home.
2. Her dose is 0.22 mg/kg of norgestimate and 0.026 mg/kg of ethinyl estradiol. This is not enough to cause a significant risk, so you induce emesis to try to recover some of the large amount of plastic she ingested and put her on a high-fiber diet to help the remainder pass without causing an obstruction.
3. Her dose is 0.31 mg/kg of norgestimate and 0.036mg/kg of ethinyl estradiol. You are concerned about the amount of estrogen ingested, so you monitor a CBC every 3-4 days for the next two weeks.

The correct answer is 2. These doses aren't at the level of concern (10 mg/kg for progestins and 1 mg/kg for estrogens). Ingesting most of the plastic could be an issue, however. The doses are correct because there are only 21 active pills in most (but not all) birth control packs.

Answer 1 is not correct, as the dose is for 28 pills. Remember, you never want to give activated charcoal and send a pet home without monitoring for hypernatremia first. Plus, you wouldn't want to give activated charcoal in a case where no significant signs are expected.

Answer 3 is not correct because the dose is based on 30 pills and the ethinyl estradiol dose is only 0.036 mg/kg, well below the 1 mg/kg trigger dose that can cause aplastic anemia and bone marrow suppression.