Use of allergy medications and repeat doses

Patient: My granddaughter,who is 15 has an allergy and being taking ZERTEC for years…Today she took ALLER-TEC instead and it didn’t improve her condition for 3hours now…How soon after ALLER-TEC can she take ZERTEC?

Doctor: Both Zertec and Aller-tec have the same active component ie Cetrizine. Thus the same should not be repeated in less than 4 hours atleast after the previous dose.I hope this helps.