Birth control pills for non-gynecologists
© 2016 Roy Benaroch, MD
Note: Almost everything I write on this blog is for parents and lay-peeps. But every once in a while I write something kind of picky and technical for my medical audience. I’m not saying the rest of you shouldn’t read this, if you’re interested in this kind of thing, but today’s post isn’t the most riveting material for those of you who don’t prescribe oral contraceptive pills. But if you do prescribe ‘em, and you’d like to know what the differences are between the dozens of brands out there, this is the post you’ve been waiting for!
Oral contraceptive pills (OCPs) are fairly good at preventing pregnancy, though maybe not as good as we’d hope. Quoted failure rates in tightly-monitored clinical trials are often < 1% a year, but in more-typical use about 9 or 10 out of 100 women who rely on OCPs become pregnant. In pediatrics, OCPs are often prescribed for their non-contraceptive benefits, including reducing symptoms associated with menses and controlling acne. Most of us choose a few brands we become familiar with – probably the ones our attendings used in residency – and honestly, that’s probably good enough most of the time. But there are differences among OCPs. Curious? Read on.
Most OCPs are a combination of an estrogen – almost always ethinyl estradiol – and a progestin. The estrogen component is there to suppress the midcycle LH surge, preventing ovulation (this had once been thought to be the main way these pills work; but it turns out there are multiple, overlapping mechanisms). Estrogens also stabilize the endometrium and prevent bleeding. Old-school OCPs used to contain 80 or 100 mcg/day of estrogen, and these caused a lot of nausea, breast tenderness, edema, headaches, and weight gain. OCPs now contain 50 mcg or less; the lowest-dose pills contain 20 mcg, and one pill has 10. Lower estrogen doses are preferred for teens, but may not be as effective at decreasing breakthrough bleeding. There’s no evidence that higher or lower estrogen doses are more of less effective at contraception.
Another estrogen side effect is an increased risk of clotting, including deep vein thrombosis. This is especially a worry if there are other risk factors, like obesity or smoking. The clotting risk of birth control pills is also partially determined by the kind of progestin that’s used in the combination.
There are no “pure” progestin compounds available pharmaceutically – all of the progestins have a varying effect on testosterone receptors, too. Nogesterel and levonorgestrel have the most androgen effect, and a somewhat lower risk of clotting than newer agents. Some progestins have a slight anti-androgen effect, like drospirenone. These are associated with a higher risk of clots. Though some of these low- or anti-androgen OCPs are specifically FDA approved for the treatment of acne (Yaz and its generics), in clinical studies it appears that all of the combination OCPs have equal, modest effectiveness for this condition. Likewise, the “low-androgen” progestins may be favored to treat other hyperandrogen states, like PCOS, but the clinical differences between them appear to be minor.
So-called “minipills” are progestin-only contraceptives. They are safer for women with a clotting risk to take, but can worsen acne. Minipills do not regulate periods and may not reduce bleeding. They’re often thought of a second-line, less-effective contraception than combined OCPs, but objective data shows they’re about equally reliable.
Some pills are in bi-phasic or even tri-phasic dosing regimens, where the amount of estrogen and progestin varies over the month. There’s no great evidence that these work better or cause fewer side effects.
OCPs can also be used as continuous dosing or in an extended cycle, allowing for longer gaps between periods, or preventing menses altogether. Any combination OCP can work like this, if the placebo pills are skipped. The FDA has approved several brands (Seasonale and generic versions) specifically packaged in 90 day or longer cycles. One brand, Lybrel, can be taken every day with no placebo phase at all.
Most of the contraindications for taking combination OCPs are related to their known effect on increasing clot risk. People at a baseline high risk of clots or complications of clots should not take combination OCPs:
- Age > 35 years and smoking > 15 cigarettes a day
- History of venous thromboembolism or stroke
- Those with a known clotting disorder
- Existing multiple risk factors for cardiovascular disease (diabetes, age, hypertension) or known ischemic heart disease
- Complicated valvular heart disease
- Migraine with aura (that’s a marker for an increased risk of embolic stroke)
- Lupus (with or without antiphospholipid antibodies), cirrhosis, breast cancer or liver cancer
Most OCPs come in packs of 21 “real” pills, then 7 placebos. They’ll sometimes have a “21” in their names (like “Loestrin 21”.) Some extend the “real” pills to 24 days, meaning they’ll be fewer placebo pills and fewer days of menstrual flow. These often have a “24” in the name (like “Minastrin 24”.)
Some OCPs replace true placebo pills with ones that contain iron, usually as ferrous sulfate. They’ll often have a FE in their names (“Junel Fe 24”)
Some OCPs come in varying strengths, usually expressed as the progestin/estrogen. For example, Junel 1.5/30 has norethindrone 1.5 mg + ethinyl estradiol 30 mcg.
For estrogen component: choose lower dose for less nausea, headache, edema; choose a higher dose for more-effective control of bleeding.
For progestin: there’s no solid evidence that the choice matters, but if side effects occur, choose a different one. Avoid some (eg, Yaz) if especially worried about clots.
Many OCPs have one or more generics that should contain the same active ingredients. Some practitioners feel that the purported increased variability of generics may cause more side effects such as spotting or nausea. Certainly, for most women at least, generic products seem to work well. Here are some good, cheap choices — in parentheses I’ve explained how each one is different from the previous:
- Junel 1/20 (norethindrone 1 mg + estrogen 20 mcg)
- Similar to brand Loestrin
- Junel 1.5/30 (little higher estrogen & progestin dose)
- Cryselle (also 30 of estrogen, but with different progestin [norgesterel])
- Similar to Lo/Ovral
- Sprintec (same norgesterel, 35 mg of estrogen)
- Similar to Orthocyclen
- Zarah (different progestin, only 20 mcg of estrogen, specifically FDA approved for acne)
- Similar to Yaz
For a much more exhaustive list, search for “OCP” in the Epocrates app, then look at their “therapeutic equivalent” table. The ones listed as “no therapeutic equivalent” are often, but not always, more expensive.
edit: I added the contraindications section 10/17/2016