Distribution occurs as soon as the infusion has started and goes on during all the infusion period.
Many thanks for any advice. This problem can be simplified by considering an infusion to be multiple bolus doses. If the infusion is 100 mg over 50 minutes, then this would be similar to giving a 2 mg bolus every minute. Suppose that the distribution half life is 10 minutes. Distribution for drug given during the first 10 minutes would be nearly complete by the end of the infusion.