Dapoxetine (No, it’s supposed to do that!)

If you take or are close to someone who takes antidepressant medication, you’re probably aware that one class, the SSRIs, is particularly prone to causing sexual side effects. These effects can run the gamut from inhibition of libido, to erectile dysfunction, to a diminished or complete inability to achieve orgasm. It’s that last one that we take a look at today – a SSRI went on sale in Britain this week that is touted as inhibiting orgasm – on purpose!
This SSRI, dapoxetine, is marketed to treat premature ejaculation. Previously sold in a few European countries, it has just gone on the market in the UK as a product called Priligy.
This compound is a rather short-acting SSRI, with a half-life (that is, the time it takes your body to eliminate it) of just under two hours. Contrast that with, say, Prozac, which has a half-life of several days. Additionally, one of the compounds your body metabolizes Prozac is also an antidepressant, with a half-life of up to about two weeks. Half-lives are an important part of designing and prescribing a drug – if you have something you want around constantly (like an antidepressant), it can be nice to have something that sticks around quite awhile. That way, if you miss a dose, your brain chemistry won’t return to the bad old days before you started taking the drug – the effect of the missed dose is blunted by the fact that you’re still carrying a fair amount around in your body. That said, if your long-half-life pill isn’t working for you, and you want to switch to a new antidepressant, it can take awhile to get it all eliminated from your system. For a pill intended to be used for something episodic (like having sex), a short half-life isn’t a liability at all – in fact, it can be a desirable feature.
Back after a long hiatus – thanks for reading!

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