Know Your Pill
I'm sure most of you already know that the combination birth control pill (the Pill) has two hormones: an estrogen and a progestin. Here are a few Pill facts you might not be familiar with.
The term progestin is used for any natural or man-made substance that has properties similar to natural progesterone. When referring to the Pill, progestin simply means the Pill's synthetic progesterone.
Most Pill brands have the same type of estrogen, namely ethinyl estradiol (EE). The other type of estrogen used is mestranol.
The amount of estrogen in each pill is very small and it's usually denoted in micrograms (mcg). Different Pill brands have different EE amounts--from a high of 50 mcg (1970s brands), to a low of 15 mcg (newer ones like Minesse). Brands with 35 mcg or less are the ones most commonly used today.
[Bonus points: Looking at the picture above, spot the difference bewteen Minesse, a monophasic (all active pills have the same amount of hormones), 28-day Pill brand, and your monophasic, 28-day pill brand.]
In contrast to estrogen, Pill brands have many types of progestin. The older progestin types are usually referred to as first- and second-generation; the newer ones are called third-generation. Here's a brief list (if you're using the Pill, look at your brand and play along):
First- and Second-Generation Progestins
The amount of progestin in each pill is also very small, and it's usually denoted in milligrams (mg). However, because different Pill brands have different progestins, you can't directly compare the strength of the brands. In other words, if two Pill brands have the same progestin DOSE but different progestin TYPES, the potency can vary widely. For example, a brand with 0.5 mg levonorgestrel is not equivalent to a 0.5 mg norgestrel brand. (It's equivalent to a 1 mg norgestrel brand.) Real life applications:
A. Don't borrow pills from a friend's pack, unless your brand and hers have the same estrogen DOSE and the same TYPE of progestin. [Ideally, you should never borrow pills.]
B. When you find yourself in need of emergency contraception (EC) [inevitably, on the one weekend when seemingly all health-care practitioners in your immediate area have vanished] and you have to substitute pills from your regular Pill pack to the ones in a dedicated EC pack, make sure the DOSE and TYPE of progestin in your pills is equivalent to 0.50 mg of levonorgestrel. (A little bit more, e.g., 0.60 mg is fine, but not less than 0.50 mg.) And how exactly are you suppose to make sure?
A. Don't wait until you actually have to use the pills to figure out the equivalency. Arm yourself with this information well in advance.
B. Look for your brand here or here. For example, if you use Alesse, know that the equivalent dose is 5 pink pills.
Finally, to give you an idea of the amounts involved:
1 mcg is 1/1,000,000 of a gram
1 mg is 1/1,000 of a gram
1 gram (g) is ~ 1/30 of an ounce