The Vaughan Williams classification is one of the most widely used classification schemes for antiarrhythmic agents. This scheme classifies a drug based on the primary mechanism of its antiarrhythmic effect. However, its dependence on primary mechanism is one of the limitations of the VW classification, since many antiarrhythmic agents have multiple action mechanisms.
Chemotherapy is the use of chemical substances to treat disease. In its modern-day use, it refers primarily to cytotoxic drugs used to treat cancer.
In its non-oncological use, the term may also refer to antibiotics (antibacterial chemotherapy). In that sense, the first modern chemotherapeutic agent was Paul Ehrlich's arsphenamine, an arsenic compound discovered in 1909 and used to treat syphilis. This was later followed by sulfonamides discovered by Domagk and penicillin G discovered by Alexander Fleming.
A cough medicine is a drug used to treat coughing and related conditions. Dry coughs are treated with cough suppressants (antitussives) that suppress the body's urge to cough, while productive coughs (coughs that produce phlegm) are treated with expectorants that loosen mucus from the respiratory tract. These medicines are widely available in the form of cough syrup, also known as linctus.