Most of the time, when I take a sleep aid, I first fall asleep nice and easy. But then 3-5 hours later I start moving around a lot and it wakes me up. But my body tries to fall back asleep but then it fights itself and tries to wake up. So I end up falling asleep, and then I wake myself up again because I’m literally thrashing around in my bed, and repeat until I finally fall asleep and get a shitty 2 hour nap before my alarm. Why?
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You’re not alone. I know someone who gets that Restless Legs Syndrome when they take sleep aids. They don’t have RLS otherwise. His doctor didn’t try to figure it out, but instead just gave him a pill for the restless legs.
RLS can have the whole body moving around too, not just the legs.
This also happens to me with certain brands of diphenhydramine (Benadryl, AdvilPM, a lot of other OTC sleep aids). I don’t know the mechanism that specifically causes restlessness but I can tell you a thing or two about why people may feel different effects from the same drug.
When you take a drug, the body metabolizes it, which changes its chemical properties so that it can be eliminated or used by the body. This is done through various steps and involves a bunch of different enzymes. Because of this, only a certain percentage of the original dose will make it to its destination (the receptors that cause the intended effects). This is accounted for in the design of the drug and the recommended doses, but everyone is a little different. Some people can have enzymes that are *really good* at metabolizing a particular substance, others can have rather “lazy” enzymes that work a bit slower. Some people may have more (or less) of an enzyme. Other drugs that you take and even certain foods that you ate that day can effect how many enzymes are available to work on this drug.
For diphenhydramine, restlessness and agitation occur when too much active drug was absorbed by the body — more drug molecules survived this “first pass” than was expected.
We like to think of chemical reactions as pretty straightforward: A binds to B and you get C. But that’s not usually the case. More realistically, A *prefers* to bind to B to produce C, but if there’s no more B available, A doesn’t want to just wander around all by its lonesome. So A may also bind to D and produce E. This is where those weird “off-target” side effects can come from. You’ve got extra drug floating around but fewer available targets so that drug may start interacting with other nearby receptors that it wouldn’t normally interact with at lower concentrations
I also get RLS when I take sleeping pills. I rarely take them any more for that reason. If I can’t sleep I get out of bed for about 20 min and then come back and try it again.
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