Is loratadine less severe than zyrtec (cetirizine)?

Loratadine is weaker: When loradine (claritin) was studied the manufacturer selected the lowest dose that gave a response better than placebo but didn't have more side effects than placebo. This caused it to be a fairly weakly effective med. As it wasn't studied at higher dose i can't speak to safety of higher doses. Personally, i find zyrtec (cetirizine) to be much more effective but may be more sedating.