Last time I looked, loratadine and Clarityn were one and the same stuff. Annoyingly drug companies give their preparations special names which are not the same as the recognised names of the active ingredients - which means that the likes of myself ends up having to learn two lots of names - the generics and the proprietary, the latter being the one that everyone notices on the boxes.
There are two basic subsets, the earlier, which tend to make people drowsy - indeed some are used as premeds for operations - and the more modern, which are said to have less of an effect this way, but some folk still do get sleepy on them. All of them potentiate alcohol, but it does make me giggle when the advice on the paediatric preparations is not to drink alcohol or operate dangerous machinery whilst on them....
End of the bed observations from one physician's practice: loratadine/Clarityn seems to have longer action but take longer to build up in the bloodstream, cetirizine/Zirtek appears to give quicker relief but not hang around as well....but because we're all different, it's worth trying one if the other hasn't been effective. The newer Neo-clarityn (I've forgotten the generic name) and levo-cetirizine (I've forgotten the proprietary name
) are no more effective according to our local formulary police, and we're told very firmly not to prescribe them. There is one less sedating antihistamine which I use in exceptional circumstances, as it seems to be fairly powerful but needs three times daily dosing. The sedative ones are best for eczema associated with night time itch, but chlorphenamine/Piriton also seems to be the gold standard for allergy management generally, and is the one we tend to turn to when all else is not working - just a pity that it really does make people so drowsy.