According to the guidelines of the German Respiratory Society, an acute cold cough without clinical indications of pneumonia or other warning signs, is the domain of self-medication. The duration – up to two weeks – is pivotal for the classification "acute". From their assessment of randomised, controlled studies, the authors concluded that Ambroxol (like several herbal medicines), shortens the duration and/or reduces the intensity of cough in acute bronchitis. Dextromethorphan is recommended by the guideline authors for a dry, troublesome cough associated with an upper respiratory infection.