When should I consider prescribing antibiotics for a patient with acute sinusitis, and what are the recommended first-line options?

When to consider prescribing antibiotics for acute sinusitis: Antibiotics should generally not be prescribed immediately for acute sinusitis as most cases are viral and self-limiting. Consider antibiotics if symptoms persist for more than 10 days without improvement, or if symptoms worsen after an initial milder phase ("double sickening"), especially if there is severe localized pain (often unilateral), discoloured or purulent nasal discharge, or fever greater than 38°C. Immediate antibiotic prescription is recommended only if the patient is systemically very unwell, shows signs of a more serious illness, or is at high risk of serious complications due to pre-existing comorbidities ¹.

Recommended first-line antibiotic treatment options: For adults aged 18 years and over with non-life-threatening acute sinusitis requiring antibiotics, phenoxymethylpenicillin 500 mg four times daily for 5 days is the first-line treatment. This choice is based on its narrower spectrum and lower risk of resistance compared to amoxicillin. For patients who are systemically very unwell or at high risk of complications, co-amoxiclav is recommended first line. For those with penicillin allergy or intolerance, clarithromycin or doxycycline (for adults and young people over 12 years) are alternatives ¹.

Additional management advice: A back-up (delayed) antibiotic prescription may be offered when bacterial infection is more likely, advising patients to start antibiotics only if symptoms worsen or fail to improve after 7 days. Paracetamol or ibuprofen can be used for pain or fever. Nasal saline or nasal decongestants may be tried for congestion, although evidence for their benefit is limited. Oral corticosteroids, oral decongestants, antihistamines, mucolytics, steam inhalation, or warm face packs are not recommended ¹.