Most classes of drugs include multiple compounds. The opinions of clinicians,
manufacturers, and purchasers may differ as to whether a particular drug is
more efficacious, safer, or more cost-effective than others in its class.1 In this article, we review the types of evidence commonly
cited to support the prescribing of a particular drug rather than another
of the same class and provide a hierarchy for grading studies that compare
a drug with another of the same class, expanding on our discussion in part
A of this Users' Guide.2