Antibiotics for upper respiratory tract infections and conjunctivitis in primary care

Although upper respiratory tract infections and acute infective conjunctivitis are minor illnesses that are usually self limiting, the use of antibiotics in these disorders is high.^1-4 Two papers in the BMJ by Arroll and Kenealy and Everitt and colleagues help clarify the role of antibiotics in the treatment of uncomplicated upper respiratory tract infections and acute infective conjunctivitis in primary care.⁵,⁶

Randomised controlled trials and meta-analyses of such trials have shown that antibiotics provided mainly short term benefit and the reduction in symptoms was too limited to justify the use of antibiotics for these minor disorders.^1-4 The number needed to treat to reduce pain at two to seven days in children with acute otitis media is 15 (95% confidence interval 11 to 24) and the number needed to treat to cure one patient with a sore throat at one week is 14 (12 to 21).¹,² This is also true for the common cold and acute infectious conjunctivitis.³,⁴

The systematic review by Arroll and Kenealy found only a clinically marginal benefit of antibiotic treatment for acute (duration less than 10 days) purulent rhinitis in patients in primary care. The number needed to treat at five to eight days ranged from seven (4 to 24) to 15 (8 to 53), depending on whether the patient's background probability of cure was 85% or 38%.⁵ The benefit of antibiotics for acute purulent rhinitis may even be overestimated as a funnel plot showed only a few small studies with small or no effect.

In Western countries, withholding antibiotics for these minor complaints can be considered harmless. Although antibiotics reduce the incidence of suppurative (for example, peritonsillar abscess) and non-suppurative (for example, rheumatic fever) complications in patients with a sore throat,² the incidence of such complications has declined sharply in Western countries in the past decades. None of the 5856 patients taking placebo in trials undertaken since 1975 developed rheumatic fever. The same trend was found for the incidence of peritonsillar abscess in patients with sore throat. In a meta-analysis on acute otitis media in young children only one serious complication (mastoiditis) occurred in the antibiotic treated group and none in the controls.¹ Meta-analyses of infective conjunctivitis, the common cold, and chronic purulent rhinitis also found no complications in the placebo groups.³,⁴

Antibiotics can have negative effects such as increased antibiotic resistance and adverse side effects. In minor self limiting illnesses the harmful effects of antibiotics (nausea, vomiting, diarrhoea, and rash) may outweigh the benefits. The meta-analysis by Arroll and Kenealy showed this clearly, as the number needed to harm for acute purulent rhinitis overlapped with the number needed to treat: the number needed to harm ranged from 12 (6 to 53) to 78 (38 to 357).⁵ A similar effect was seen in acute otitis media; the number needed to harm ranged from 6.5 (3.9 to 18.1) to 170 (83 to 571).¹ Prescribing antibiotics for upper respiratory tract infections can strengthen patients' belief in antibiotics (perhaps inappropriately) and could be viewed as excessive interference by the medical profession. The randomised trial by Everitt and colleagues found that this is also true for acute infective conjunctivitis.⁶ Patients with conjunctivitis who received antibiotics immediately were more likely to say they would re-attend with subsequent eye infections than those who were not prescribed antibiotics or received them at a later date.

In major illness the risk to benefit ratio may not have an important role in the decision about treatment with antibiotics—usually there is no choice. Antibiotic treatment is more effective in certain subgroups of patients (such as those with confirmed bacterial infection), and in others treatment might be necessary to prevent a severe course of disease. A meta-analysis of patients with a sore throat found that on day 3 antibiotics reduced symptoms in patients with a culture positive infection with Streptococcus species compared with those with a negative culture; the number needed to treat ranged from 6.5 (6.1 to 7.3) to 10.2 (8.0 to 13.3).²

To help doctors identify these subgroups, diagnostic or prognostic indices are needed that can identify a bacterial cause of disease at an early stage. Such a diagnostic index for people with acute infective conjunctivitis was published in the BMJ in 2004.⁷ However, further research is warranted, including meta-analyses of data on individual patients from the original trials on upper respiratory tract infections and acute infective conjunctivitis, which may show who would benefit most from antibiotic treatment.⁸,⁹

What does all this imply for daily practice? Although antibiotics shorten the duration of symptoms and protect against complications, the benefit is small and often absent. Patients can be protected from complications only by treating many who will not benefit and may actually be harmed by the treatment. The evidence indicates that reserved prescribing of antibiotics for upper respiratory tract infections and acute infective conjunctivitis is justified.

Delayed prescription of antibiotics is a good alternative for patients with a progressive course of disease or for those patients with a strong preference for antibiotics; it is a safe strategy to reduce the number of prescriptions in patients with upper respiratory tract infections and acute infective conjunctivitis.⁶,¹⁰