Enhancing Amoxicillin Pharmacokinetics and Pharmacodynamics Parameters With Probenecid in Bone and Joint Infections

NCT07764302 | Not Yet Recruiting Phase 3

• 2 other identifiers: APHP2512292026-525404-95-00
• Study Type: interventional
• Target: 57
• Locations: 1 country
• Sites: 8

Brief Summary

Osteoarticular infections (OAIs) are common, with Streptococcus spp. and Enterococcus spp. being the second most common causative pathogens after Staphylococcus aureus. High-dose oral amoxicillin is recommended as first-line treatment for susceptible infections caused by Streptococcus spp., Enterococcus faecalis and anaerobic bacteria. However, treatment failure remains frequent despite appropriate therapy, with reported rates ranging from 25% to 48%. The efficacy of β-lactam antibiotics is closely related to PK/PD target attainment, particularly the time during which free drug concentrations remain above the minimum inhibitory concentration (fT \> MIC). For severe infections such as OAIs, maintaining antibiotic concentrations above the MIC throughout the dosing interval is considered the optimal PK/PD target. Because amoxicillin penetration into bone is limited (bone-to-plasma concentration ratio 0.1-0.3), a trough plasma concentration (Cmin) ≥10 × MIC has been proposed to ensure adequate exposure at the site of infection. Achieving this target is particularly challenging for E. faecalis because of its higher MICs and the saturable oral absorption of amoxicillin at doses ≥2 g. Accordingly, the French Infectious Diseases Society (SPILF) recommends PK/PD-guided dose optimization and therapeutic drug monitoring when oral amoxicillin doses exceed 9 g/day. Probenecid inhibits the renal tubular secretion of β-lactams through inhibition of OAT1 and OAT3 transporters, thereby increasing plasma amoxicillin concentrations and prolonging its elimination half-life. This pharmacokinetic interaction has been well documented and may improve PK/PD target attainment without increasing the amoxicillin dose. Current national recommendations advocate high-dose amoxicillin but propose heterogeneous dosing regimens, resulting in substantial variability in prescribing practices. The AMPHORE study aims to generate clinical PK/PD data to establish standardized dosing strategies for oral amoxicillin, with or without adjunctive probenecid. Hypothesis : In patients with osteoarticular infections treated with oral amoxicillin, the addition of probenecid may improve amoxicillin PK/PD target attainment by increasing trough plasma amoxicillin concentrations. Objective : To evaluate the effect of adding oral probenecid on the trough plasma amoxicillin concentration in patients receiving oral amoxicillin monotherapy for osteoarticular infection. Method : Prospective, multicentre, quasi-experimental before-and-after study conducted in eight French hospitals. Fifty-seven patients with microbiologically confirmed osteoarticular infections caused by amoxicillin-susceptible pathogens (Enterococcus spp., Streptococcus spp., Cutibacterium spp. or other amoxicillin-susceptible anaerobic bacteria) receiving oral amoxicillin monotherapy will be included. Following baseline pharmacokinetic sampling, patients will receive oral probenecid (500 mg every 8 hours), with repeat pharmacokinetic assessment.

Conditions

Osteoarticular Infections (OAIs)

Keywords

Amoxicillin; Probenecid; Osteoarticular infections; Pharmacokinetics/pharmacodynamics (PK/PD)

Outcome Measures

Primary Outcomes (1)

• Achievement of the amoxicillin PK/PD target (Cmin ≥ 10 × MIC)

  The proportion of patients achieving a trough plasma amoxicillin concentration ≥ 10 × the MIC of the causative bacterium (corresponding to 100% of the time spent at concentrations ≥ 10 × MIC in plasma between two amoxicillin doses), with or without probenecid.

  At baseline before probenecid initiation and after 24-72 hours of probenecid treatment.

Secondary Outcomes (16)

• Clinical and biological treatment success at end of treatment and 6-month follow-up

  At the end of antibiotic treatment and 6 months ± 7 days after treatment completion.

• Comparison the complete pharmacokinetic parameters of amoxicillin in normorenal adults treated for osteoarticular infection with amoxicillin without and with probenecid.

  24-72 hours after probenecid initiation

• Comparison the complete pharmacokinetic parameters of amoxicillin in normorenal adults treated for osteoarticular infection with amoxicillin without and with probenecid.

  24-72 hours after probenecid initiation

• Comparison the complete pharmacokinetic parameters of amoxicillin in normorenal adults treated for osteoarticular infection with amoxicillin without and with probenecid.

  24-72 hours after probenecid initiation

• Comparison the complete pharmacokinetic parameters of amoxicillin in normorenal adults treated for osteoarticular infection with amoxicillin without and with probenecid.

  24-72 hours after probenecid initiation

Study Arms (1)

Amoxicillin-probenecid combination therapy

EXPERIMENTAL

Addition of probenecid to oral amoxicillin therapy.

Drug: Oral probenecid added to oral amoxicillin for osteoarticular infections

Interventions

Oral probenecid added to oral amoxicillin for osteoarticular infections DRUG

Adjunctive oral probenecid (500 mg every 8 hours ± 1 hour) added to ongoing oral amoxicillin in adult patients treated for microbiologically documented osteoarticular infections. Probenecid is administered for pharmacokinetic assessment to evaluate its effect on amoxicillin exposure and PK/PD target attainment. Amoxicillin dosing (2 or 3 g every 8 hours ± 1 hour) remains unchanged before and after probenecid administration. Probenecid will be administered for 24-72 hours for pharmacokinetic assessment. It may subsequently be continued until the end of antibiotic treatment if the amoxicillin trough concentration is below 10 × MIC without probenecid but reaches the target with probenecid, in accordance with the protocol.

Amoxicillin-probenecid combination therapy

Eligibility Criteria

• Age: 18 Years+
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• Age ≥ 18 years old
• Effective contraception throughout the study period for women of childbearing potential.
• Ongoing oral amoxicillin monotherapy for the treatment of a documented osteoarticular infection, including: osteoarticular infection without implanted material (arthritis, osteitis, osteomyelitis), osteoarticular infection involving implanted material (osteoarticular prosthesis, osteosynthesis hardware, external fixator, or arthrodesis material excluding spinal instrumentation), or spondylodiscitis with or without implanted material, defined by the following criteria:
• Microbiological documentation of one or more pathogens for which amoxicillin is the recommended antibiotic treatment (Enterococcus spp. susceptible to ampicillin, Streptococcus spp., Cutibacterium spp., and other anaerobic bacteria susceptible to amoxicillin), obtained from blood cultures, disco-vertebral biopsy, bone biopsy, joint aspiration, and/or intraoperative samples.
• Treatment with oral amoxicillin monotherapy for the management of this osteoarticular infection, with the diagnosis established based on the following criteria:
• Clinical signs, with one or more of the following: fever, hypothermia, chills, pain, spinal pain, arthritis, inflammatory or dehiscent scar over osteoarticular hardware, fistula, purulent drainage, and/or
• Suggestive radiological findings (X-ray, CT scan, or MRI): bone lysis, periosteal reaction, sequestrum, soft tissue collection, joint effusion, radiolucent line around osteoarticular hardware suggestive of loosening. In cases of spondylodiscitis: T2 hyperintensity of the disc, T1 hypointensity of adjacent vertebral endplates on MRI, posterior facet joint arthritis, and/or
• Final diagnosis of osteoarticular infection established by the treating medical or multidisciplinary surgical team based on a combination of clinical, microbiological, radiological, or other relevant findings.
• Patients with a history of one or more previous osteoarticular infections are eligible.
• Oral amoxicillin treatment permitted based on clinical and biological improvement.
• Patient informed and having provided written informed consent to participate.

You may not qualify if:

• Pregnancy or breastfeeding.
• Severe allergy to β-lactams or documented allergic contraindication to penicillins confirmed by allergy testing.
• Contraindication to probenecid, including: hypersensitivity to probenecid, an ongoing acute gout attack, nephrolithiasis, secondary hyperuricemia due to chemotherapy, radiotherapy, or myeloproliferative syndrome because of the increased risk of uric acid nephropathy, and primary hyperuricemia due to uric acid overproduction.
• Ongoing treatment, which cannot be discontinued, with a medication known to interact with probenecid: methotrexate, diprophylline, cholestyramine, phenobarbital, and zidovudine. If treatment discontinuation is possible, the washout period will be left to the investigator's discretion.
• Body weight \<40 kg or \>110 kg.
• Patients under legal guardianship, curatorship, judicial protection, or deprived of liberty.
• Patients with cognitive impairment or who, in the investigator's opinion, are unable to understand the study, participate in all study visits considering the treatments and procedures required by the protocol, and/or provide informed consent.
• Patients not affiliated with a social security system or another health insurance scheme, including patients covered by State medical aid (AME).
• Concomitant participation in another clinical trial involving a medicinal product for human use, a clinical investigation of a medical device, or any interventional research involving human participants.
• Participation in non-interventional research is permitted

Sponsors & Collaborators

• Assistance Publique - Hôpitaux de Paris: lead

Study Sites (8)

Hôpital André Mignot, Centre Hospitalier de Versailles

Chesnay, 78150, France

Location

Hôpital Beaujon AP-HP

Clichy, 92110, France

Location

Hôpital Henri-Mondor, AP-HP

Créteil, 94010, France

Location

Hôpital Cochin Port Royal, AP-HP

Paris, 75 014, France

Location

Hôpital Lariboisière-Fernand Widal, AP-HP

Paris, 75010, France

Location

Hôpital Saint-Antoine - AP-HP

Paris, 75012, France

Location

Hôpital Ambroise-Paré, AP-HP

Paris, 92100, France

Location

Hôpital Bretonneau, CHU Tours

Tours, 37000, France

Location

Study Officials

• Souhail Bérénice

  AP-HP. Hôpitaux Universitaires Henri Mondor

  PRINCIPAL INVESTIGATOR

Central Study Contacts

Souhail Bérénice, Dr

CONTACT

+33 1 49 81 24 55; berenice.souhail@aphp.fr

Raphaël Lepeule, Dr

CONTACT

+33 1 49 81 24 55; raphael.lepeule@aphp.fr

Study Design

• Study Type: interventional
• Phase: phase 3
• Allocation: NA
• Masking: NONE
• Purpose: TREATMENT
• Intervention Model: SINGLE GROUP
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Model Details: A multicenter, non-randomized, comparative, quasi-experimental before-and-after study conducted in adult patients treated with oral amoxicillin monotherapy for an osteoarticular infection.

Study Record Dates

• First Submitted: July 31, 2026
• First Posted: August 13, 2026
• Study Start (Estimated): December 1, 2026
• Primary Completion (Estimated): December 1, 2028
• Study Completion (Estimated): September 1, 2029
• Last Updated: August 13, 2026

Record last verified: 2026-08

Data Sharing

• IPD Sharing: Will not share

Locations

FR (8)