The current prescription writing behavior of physicians is largely an informed decision based upon education and experience. The physician typically assesses the signs and symptoms of a patient presentation, laboratory and other clinical tests, and other factors that may be known to the physician (e.g. an inability to swallow capsules, or a requirement to be in direct sunlight for an extended period), and chooses a drug to prescribe with no evidence of patient response to the agent prescribed. The prescribing physician may or may not decide to validate this decision by additional testing in the form of follow-up visits or other procedures that are designed to assess the effectiveness of the prescription after some arbitrary period of time, but not comparatively with other available agents.