Call the Trade Descriptions office: this so-called sex comedy features very little sex, which is fine, and absolutely no comedy, which is not.
Emma (Natalie Portman) and Adam (Ashton Kutcher) have met one another off and on since their teens and finally decide to get together purely for sex: she's an ambitious ER doctor with an allergy to "emotions" and he's a bloke who likes getting his end away, so the relationship seems to suit them both. The film might have redeemed this charmless arrangement if it had been remotely funny, but Elizabeth Meriwether's script goes, as it were, from bed to worse. Portman, so great in Black Swan, is a nightmare of vulgarity here. Her playing drunk and sluttish would be an unappealing sight at best, but playing drunk and sluttish for the sake of Kutcher is frankly insupportable.
Fighting gamely against the comic void are Greta Gerwig, as Emma's doctor pal, and Lake Bell, who does wonders as a TV producer besotted with Kutcher (no small feat). The latter would have been so much better suited than Portman to this carefree single gal. No strings attached, but you might care to bring your own noose.