Loratidine stopped working. Should I switch or add something else, like zyrtec (cetirizine)?

Zyrtec vs claritin (loratadine) Loratidine (claritin) is the most ineffective antihistamine ever approved for market. Its effect is weak and can take a long time to work. Zyrtec is stronger but a little more sedating, 13% vs 8% (loratidine). It can be taken alone or in combination with loratidine or fexofenadine. The latter is the least sedating of the three and about as potent as cetirizine.