Abstract: A first aspect of the invention is a method of estimating a withdrawal interval for an adjusted dose of a compound from a prior withdrawal time for a corresponding prior dose of that compound, corresponding half-life data and a tolerance concentration, for a tissue of interest. The method comprises selecting an adjusted dose for the compound for which a withdrawal interval is to be determined, and extrapolating a withdrawal interval from (a) the prior dose, (b) the prior withdrawal time, (c) the half-life data, and (d) the tolerance concentration. The process is useful for determining a withdrawal interval for an extralabel (i.e., non-approved) use of a drug in the same or a different jurisdiction for which a previous use has been approved, and can be used to determine an appropriate withdrawl interval for a drug in food products exported from one jurisdiction to another. Data processing systems and computer program products for carrying out the foregoing are also disclosed.