Dr.Nissen points out that many over the counter drugs - aspirin,ibuprofen, acetaminophen or paracetamol - can be toxic if used improperly.

VOA: standard.2010.03.02

Generally these are called over-the-counter contracts because they're not arranged through exchanges.

通常来说 它们被称为场外交易合同,因为这种交易是在交易所之外进行的

耶鲁公开课 - 金融市场课程节选