How Drugs Work: The Morning After Pill

I have written before, elsewhere, about the pill and how it works, but the other day I was wondering… does the morning after pill work in the same way? I think I may also have said before, here or elsewhere, I can’t keep track of my own ramblings, that I think contraception and emergency contraception are hugely important and valuable things to have. They’re a very empowering tool for women, they let you take control of your body to a certain extent. This doesn’t mean that I advocate the regular use of the morning after pill, emergency contraception is for emergencies, after all, but if something does go wrong, or fail, or worse, if you’re the victim of sexual assault or rape, the ability to try and prevent unwanted pregnancy is, to me, just invaluable. It’s a way to take some control of your situation. And that we can do this, we have the knowledge and ability and understanding to take that control… that’s just amazing.

So, anyway, how does it work? I’ve explained the menstrual cycle before, when I was discussing the pill, but to recap (and blatantly repeat myself), this is how it goes down…

Hormones are the messenger system of the body, they dart around the place attaching themselves to cells and relaying instructions to make them do things, or stop doing things, or do more of a specific thing. In my head, hormones have loudspeakers and clipboards and are called efficient-sounding names like Barbara and Robert. The whole of your reproductive cycle is a delicately balanced system of hormones, all shouting instructions at cells at exactly the right moment, culminating in the production of an egg, ready to be fertilised.
In addition to progesterone and oestrogen, there are a few other key hormones involved. Together, they form Team Reproduction. Some of them even have capes to match their clipboards. They are gonadotropin-releasing hormone (GnRH), follicle stimulating hormone (FSH) and luteinising hormone (LH).  The instigator in the process in GnRH, it is produced by the hypothalamus in the brain and production is regulated by progesterone. On production it races off to the anterior pituitary gland, there to shout at cells until they start producing FSH.  FSH, once produced by the pituitary gland, flies down to the ovaries and tells them that it’s time to start prepping the egg, which they do by growing follicles, one of which will become an egg when it grows up. Although it would probably rather be a ballerina, it doesn’t get that option. The ovaries, alongside their egg-prepping, start to release oestrogen, which scoots back up to the brain to tell the pituitary gland to slow down on the FSH production. At the same time, another deputation of oestrogen hormones are busy encouraging the hypothalamus to produce even more GnRH. Because by this time the hypothalamus probably needs some moral support or something.
This oestrogen cheerleading squad results in a sudden increase in GnRH production from the hypothalamus, which tells the pituitary gland to stop messing around with FSH and produce a mega-load of LH. Pretty soon an squad of LH molecules has amassed, and once this cheerleading squad is ready it marches upon the ovaries chanting “IT’S GO TIME”. And the ovaries release the egg. If there’s a sperm in the area and all the conditions are right then, in short, a baby gets made.
Where other contraceptive pills can try and stop this happening at an earlier stage, by stopping the egg being developed and produced in the first place, the role of the morning after pill is to stop pregnancy occurring at this point.
It is thought to do this by attempting to delay the egg being released, to try and stop it coming into contact with the sperm. Because levonorgestrel, the active drug in the morning after pill, is an international hormone of mystery, it’s not 100% clear how it actually does this. The theory is that levonorgestrel is a synthetic progesterone-like hormone, a very clever spy of a hormone disguised as progesterone.  Very high levels of  hormones-pretending-to-be-progesterone, when taken in pill form, effectively just go into your system and really screw everything up. This is possible because your  hormone cycle is really delicately balanced, so an influx of any one hormone can really throw things of course. A temporary surge in progesterone (or stealthy fake progesterone in this case) from a morning after pill can theoretically cause sufficient havoc to delay release of the egg and prevent it meeting up and getting frisky with a sperm.

This is how I envisage the morning after pill, with it’s sneaky progesterone hat disguise on.

There is also a further theory that levonorgestrel might make it difficult for a fertilised egg to implant into the wall of the uterus. This would mean that even if the egg and the sperm did manage to meet up, like star crossed lovers in your fallopian tubes, they still couldn’t make a baby, because they’d have nowhere to settle down and get it on.
So that’s how it works, a clever international spy hormone of mystery sneaks into your system and causes minor chaos for long enough that the egg and the sperm are kept apart. It sounds very much like a molecular James Bond movie, actually. The only risk is that if you do have unprotected sex at just the wrong moment, and the sperm and the egg meet, fall in love and settle down together happily in the wall of the uterus before you get a chance to take the morning after pill, there’s nothing that levonorgestrel can do. This is why doctors advise women to take the morning after pill as soon as possible after having unprotected sex, and certainly within 72 hours. The quicker you take it, the more likely it is that the James Bond hormone can get involved and call a halt to proceedings. Before drinking a cocktail, naturally.
*As ever, I am an enthusiastic science nerd, not a doctor, if you think you need to take the morning after pill, you need to speak to your doctor or a pharmacist now. Right now. Stop listening to me and go… thanks*
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