A drug dispenser for administering a drug solution ophthalmically. The dispenser comprises a cylindrical member having an open proximal end, a distal end having a hole for dispensing the drug solution, and a connecting passage formed in a sidewall thereof. A plunger is receivable in the proximal end of the cylindrical member and the member is axially slidable on the plunger between a non-mix position and a mix position. The dispenser further comprises a piston having a distal end and a proximal end and slidably disposed within the cylindrical member in sealing engagement therewith. The distal end of the piston is located proximally of the passage and forms a drug chamber with the distal end of the member for storing a drug when the member is in its non-mix position. The proximal end of the piston is distally spaced from the plunger to form a diluent chamber therebetween for storing a diluent when the cylindrical member is in its non-mix position. When the cylindrical member is moved to its mix position the drug chamber and diluent chamber are in fluid communication and the diluent is free to flow through the passage to mix with the drug to form the drug solution.
