Why is it that the side effects listed for many medications will often include polar opposites?
In other words, it’s not uncommon to hear or read something to the effect of “Side effects may include diahrea/constipation, sleepiness/insomnia, drowziness/excitability…”, etc.
How is it that a medication may have one effect, but also may have the complete opposite effect?
They’re covering all their bases. Yup, gotta CYA in this sue-happy country.
Many drugs have initially a sedating effect, but if you take too much make you wired. If you’ve ever taken too much cold medicine, you know what I mean. Also, people can react differently to the same drug.
The side effects reported on drug labels, inserts, and advertising are those reported during clinical trials. There are two main reasons why these may seem paradoxical:
All adverse events are reported, even those which may seem unrelated to the drug. If you can’t prove it’s unrelated, you have to list it on the label. The “likely side effects” are given first, and those were reported in a large number of subjects, and are most likely to be related to the drug.
People are different. Sudafed makes my wife drowsy, whereas it makes most people a little hyper (it makes me twitch). There may be a whole bunch of receptors in my wife’s system where most people don’t have many. Most of the paradoxical reponses are unexplained.