The manuscript is available in postscript and pdf format. Phase I addresses side effects and such issues as drug metabolism. Phase II addresses the relationships between dose and effectiveness and between dose and side effects.
Assignment is random, usually with equal numbers of patients assigned to each dose.
Based on the results of the trial, a decision is made to either enter phase III in the drug's development, stop the drug's development, or conduct another phase II trial. Such a design is inefficient, in terms of both time and resources. If the drug is effective then the dose-response curve has a positive slope for some dose. The sloping part of the curve may be located at doses greater than or less than those considered in the trial. In either case many of the observations at the opposite end from where the greatest slope occurs may be wasted.