Chinese medicinal herbs for influenza

Background Influenza is a communicable acute respiratory infection which, during epidemics, can cause high morbidity and mortality rates. Traditional Chinese medicinal herbs, often administered following a particular Chinese medical theory, may be a potential treatment of choice. Objectives To assess the effect of Chinese medicinal herbs used to prevent and treat influenza and to estimate the frequency of adverse effects. Search methods We searched CENTRAL (2012, Issue 11), MEDLINE (January 1966 to November week 2, 2012), EMBASE (January 1988 to November 2012) and CNKI (January 1988 to 29 March 2012). We also searched reference lists of articles and the WHO ICTRP search portal (November 2012). Selection criteria Randomised controlled trials (RCTs) comparing traditional Chinese medicinal herbs with placebo, no treatment or conventional medicine normally used in preventing and treating uncomplicated influenza. Data collection and analysis Two review authors independently extracted data and assessed trial quality. Main results We included 18 studies involving 2521 participants. The methodological quality of 17 included studies was poor. Included RCTs separately compared medicinal herbs with different antiviral drugs, precluding any pooling of results. Only three indicated that compared with antiviral drugs, Chinese medicinal herbs may be effective in preventing influenza and alleviating influenza symptoms. 'Ganmao' capsules were found to be more effective than amantadine in decreasing influenza symptoms and speeding recovery in one study (in which adverse reactions were mentioned in the amantadine group although no data were reported). There were no significant differences between 'E Shu You' and ribavirin in treating influenza, nor in the occurrence of adverse reactions. Ten studies reported mild adverse reactions. Authors' conclusions Most Chinese medical herbs in the included studies showed similar effects to antiviral drugs in preventing or treating influenza. Few were shown to be superior to antiviral drugs. No obvious adverse events were reported in the included studies. However, current evidence remains weak due to methodological limitations of the trials. More high-quality RCTs with larger numbers of participants and clear reporting are needed.