If you travel with PEG, aka MiraLax, GlycoLax, RestoraLax, ClearLax (or similar names), i.e. laxatives based on polyethylene glycol 3350 powder, be aware of yet another LHR peculiarity: it shows the same as liquid to their X-ray scanners, so they'll pull apart (slowly) your hand luggage and delay you further.

Pull it out and put it in the bin so that it scans separately and they don't automatically delay you for a bag search.

No problems with it in the US and many other EU countries; it is powder after all. LHR "security", as we know, is special.