The Effect of Losartan on Cephalexin (KEFALOS)

The goal of this clinical trial is to investigate the effects of the blood pressure-lowering drug losartan on the blood levels and urinary excretion of the antibiotic cephalexin during simultaneous and staggered ingestion in healthy volunteers. The main questions it aims to answer are: 1. Does losartan affect cephalexin levels and excretion when ingested at the same time? 2. Does a three-hour interval between ingestion of losartan and cephalexin eliminate a possible effect? Researchers will compare the effects of losartan ingested at the same time, losartan ingested three hours prior, and no losartan ingested on oral cephalexin in each participant to see whether an interaction exists and could be avoided. Participants will visit the research laboratory on three days during which they will ingest single doses of losartan at the same time with, three hours prior to, and not at all prior to ingesting single doses of cephalexin.

• Plasma concentrations of cephalexin over time, the cumulative urinary excretion of cephalexin, and the pharmacokinetic parameters derived from these measurements following simultaneous or staggered ingestion of losartan

1. Last registry update

   1 Oct 2026

2. Primary completion

   8 May 2026

3. Started

   4 Mar 2026

4. Registered

   24 Dec 2025