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Research project

Cellulitis optimal antibiotic treatment (COAT) study

Project overview

This NIHR Health Technology Assessment Board funded study aims to determine whether a short course (5 days) of antibiotics is as good as a standard course (7 days) in patients with cellulitis in the leg in primary care.

Cellulitis is a common, and potentially serious, deep skin infection. It is particularly common in older people, and most commonly occurs in the legs. NICE recommend 5-7 days of the oral antibiotic flucloxacillin for most patients managed in primary care, but over 90% of patients are treated for 7 days or more. Shorter courses of antibiotics have been shown to be as effective as longer courses for many infections, including serious infections like pneumonia, and have the potential to reduce adverse effects and the development of antimicrobial resistance.

The trial will recruit patients from participating general practices who have cellulitis in the leg and a pain score of 3 or more. All participants will be prescribed oral flucloxacillin for 5 days and will be randomly allocated to receive an additional 2 days of flucloxacillin or a matched placebo, to take after the initial 5-day course. The primary outcome is pain over days 6-14. We will also measure recurrent symptoms requiring additional antibiotics, patient-rated unwellness, EQ5D, mobility, self-care, time to recovery, complications and recurrence. Economic effects will be explored by a cost-consequences analysis over a 12-month horizon.

The study will run over 4 years and will help inform practice in the NHS and around the world. If a short course is shown to be as effective as a longer course this could result in ~30% reduction in exposure to antibiotics, which could have important implications for antimicrobial resistance and patient outcomes.

The study is being run by researchers in the University of Southampton Primary Care Research Centre in collaboration with the Clinical Trials Unit, researchers at the University of Nottingham, University of East Anglia and Norfolk and Norwich University Hospitals, and public contributors.

Further information on the COAT study can be found by following this link:


Lead researcher

Professor Nick Francis

Head of School

Research interests

  • Infections in primary care
  • Antimicrobial stewardship
  • Respiratory infections
Other researchers

Professor Paul Little

Professor in Primary Care Research

Professor Andrew Cook MBBS MPH FFPH

Professorial Fellow in HTA

Research interests

  • Pragmatic Clinical Trials
  • Research Conduct
  • Guidelines

Professor Miriam Santer

Professor of Primary Care Research

Research interests

  • Self-management of long-term conditions
  • Primary Care Dermatology - particularly eczema, acne and cellulitis
  • Mixed methods research including development and evaluation of complex interventions

Professor Robert Read

Chair of Infectious Diseases

Collaborating research institutes, centres and groups

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