This is random - is pseudoephedrine the stuff that makes you sleepy? Because we used to give Benedryl to our pets as a mild sedative (car trips), but Benedryl in the UK does not contain the same ingredients & therefore is ineffective. Will this Boots pseudoephedrine do the trick?
(sorry to hi-jack!)
No, psuedoephedrine is non-drowsy (in fact, as it can increase your heart rate, it can keep you awake, not send you to sleep!).
However, Benadryl usually does not contain pseudoephedrine anyway - pseudoephedrine is a decongestant and Benadryl is an antihistamine... they are two different types of medicine.
In the US, Benadryl contains diphenhydramine, which is a drowsy antihistamine, but in the UK Benadryl contains either cetirizine (1-a-day and usually non-drowsy) or acrivastine (also non-drowsy), so it doesn't make you sleepy.
But, there is a UK product called Benadryl Plus which contains both an antihistamine (acrivastine) and a decongestant (pseudoephedrine)... but again, this product won't make you sleepy either

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A quick note about giving medicine to pets though: medicine licensing laws state that pharmacies can only sell medicines for use in/on humans, so you cannot buy anything over the counter for a pet because it is breaking licensing laws - you must get it through your vet instead (we had a customer really kick off yesterday because she wanted to buy eye drops for her dog and we were not allowed to them sell to her). Even if your vet tells you that you can buy it over the counter, the pharmacy is not allowed to sell it for use on animals.