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NCT Number: NCT07300670

The Effect of Losartan on Cephalexin

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.

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Key information

Conditions

Possible Interaction Between Losartan and Cephalexin Healthy

Age range

18 year–40 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Phase 1

Primary location

Unit of Clinical Pharmacology, Turku University Hospital

Turku, Southwest Finland, FI-20520, Finland

Location status: Recruiting

Location contact

Aleksi Tornio, M.D., Ph.D.

CONTACT

[email protected]

+358504765715

Aleksi Tornio, M.D., Ph.D.

PRINCIPAL_INVESTIGATOR

Mikael OW Piha, M.D.

SUB_INVESTIGATOR

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • written informed consent
  • 18-40 years of age
  • good health
  • systolic blood pressure of at least 115 mmHg
  • all screening laboratory results (P-Krea, Pt-GFReEPI, P-Na, P-K, P-ALAT, P-AFOS, P-GT, B-PVK+T) acceptable; minor deviations from reference ranges are acceptable at the discretion of a physician-scientist with the exceptions of Pt-GFReEPI which must be at or above the reference limit and P-K which must be at or below the higher reference limit (Reference limits: Tyks Laboratories, Turku University Hospital)
  • regarding female subjects, a negative pregnancy test (S-HCG-O) before the study, and the use of a highly effective contraceptive method (e.g. copper intrauterine device, bilateral tubal occlusion, vasectomised partner, or abstinence from heterosexual intercourse), according to CTFG Recommendations related to contraception and pregnancy testing in clinical trials, are required

Exclusion criteria

  • inability to provide written informed consent in Finnish
  • remarkable illness
  • confirmed or reasonably suspected allergy to cephalexin, amoxicillin, benzylpenicillin, phenoxymethylpenicillin, piperacillin, cefaclor, or cefamandole
  • confirmed or reasonably suspected severe delayed allergic reaction to any beta-lactam antibiotic
  • underweight (BMI less than 18.5 kg/m2)
  • obesity (BMI greater than 30 kg/m2)
  • smoking
  • regular medication, including hormonal contraception in the form of pills, intrauterine device, subdermal implant etc.
  • current or planned pregnancy, and breastfeeding
  • less than three months elapsed since a prior clinical trial
  • less than three months elapsed since donating blood

Treatment and study plan

Losartan

Drug

100 mg tablet orally, single dose

Other names: Cozaar

Cephalexin

Drug

500 mg tablet orally, single dose

Other names: Kefalex, Kefexin

Primary outcomes

  1. 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

    Time frame: up to 8 hours after ingestion of cephalexin on three consecutive days separated by at least one-week intervals

Secondary outcomes

  1. Plasma concentrations of losartan and losartan carboxylic acid over time, the cumulative urinary excretion of losartan and losartan carboxylic acid, and the pharmacokinetic parameters derived from these measurements

    Time frame: up to 11 hours after ingestion of losartan or water on three consecutive days separated by at least one-week intervals

    following simultaneous and staggered ingestion of cephalexin

Other outcomes

  1. Plasma and urinary concentrations of endogenous and diet-derived metabolites, and the effects of genetic variants and other individual factors on the pharmacokinetic parameters of cephalexin and losartan

    Time frame: up to 11½ hours on three consecutive days separated by at least one-week intervals

Study contacts

Contact information is provided by the study sponsor or research team.

Aleksi Tornio, M.D., Ph.D.

CONTACT

[email protected]

+358504765715

Sponsors and collaborators

Lead sponsor

Aleksi Tornio

Other Gov

Collaborators

  • Helsinki University Central Hospital
  • Turku University Hospital
  • University of Helsinki
  • University of Turku

Registry information

Acronym: KEFALOS

Important dates

Study start
2026
Primary completion
2026
Study completion
2026
First posted
Dec 24, 2025
Registry last updated
Mar 25, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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