Azithromycin, often prescribed by doctors in the United States, has been found ineffective for treating bronchitis. This has been found in a randomised, double-blind, controlled trial by Dr Arthur Evans and colleagues at the Collaborative Research Unit, Cook County Hospital, Chicago Illinois, which compared azithromycin with low dose vitamin C. Dr Evans found “that azithromycin is no more effective than low-dose vitamin C for treatment of acute bronchitis. Given the lack of evidence that low-dose vitamin C is beneficial, we conclude that azithromycin is ineffective and should not be prescribed for patients with acute bronchitis.” Every year, more than 10 million American adults see their doctors for acute bronchitis, and most receive antibiotics. “Many experts condemn such treatment, citing three main reasons: weak or conflicting experimental evidence of clinical benefit, lack of a strong biological rationale (the causative pathogens are viruses in most cases), and increasing societal concern about widespread antibiotic resistance.” Azithromycin, a macrolide antibiotic commonly prescribed for acute bronchitis, has a broad spectrum of activity and infrequent adverse effects, and is easy to take (once daily for five days). However, it is also expensive, and the only published evidence of its efficacy in acute bronchitis comes from several small equivalence studies. The researchers investigated whether treatment with azithromycin allows people to return to work earlier, and provided greater improvements in health-related quality-of-life scores, compared with low-dose vitamin C.