Abstract: A dual-chamber cylinder ampoule is used for the mixture of a sensitive, solid medicament, with liquid which is caused to flow calmly through the medicament in order to avoid any shaking and mechanical influence. The mixing is preferably carried out at a pressure above atmospheric.An injection device for the preparation of an injection solution and a following injection of such solution includes first and second tubular members for enclosing and holding a dual-chamber cylinder ampoule, in which the dry medicament is kept separated from the liquid. When the two tubular members are being screwed together the liquid is calmly and gently mixed with the dry medicament and dissolves it, and the resulted solution can thereafter be injected by means of the dosage and administration mechanism, provided in one tubular member, through a needle arranged at the front end of the other tubular member.