HPLC assays to simultaneously determine the angiotensin-AT1 antagonist losartan as well as its main and active metabolite EXP 3174 in biological material of humans and rats.

Novel rapid and sensitive HPLC assays were developed to simultaneously determine losartan and its main active metabolite EXP 3174 in biological material of humans and rats following solid-phase or liquid-liquid extraction. The analytes were separated on a 3 microm particle-sized ULTREMEX CN column, which was preceded by a 5 microm particle-sized guard column, using UV-detection at 245 nm. The assays provided high sensitivity with limits of quantification (LoQ) of 5 ng ml(-1) for both compounds in human and rat plasma and 10 ng ml(-1) in human and rat urine, respectively. In rat blood, bile and various tissues, limits of quantifications were achieved that ranged 10-15 ng per ml and per 100 mg tissue, respectively, for both analytes.