Administration by injection or infusion to patients of an injectable liquid for diagnostic or therapeutic purposes is provided by a syringe adapter connectable with an automatic syringe pump and a syringe containing contents to be dispensed. The syringe adapter includes an adapter body receivable by the syringe pump, a syringe retainer for retaining the syringe, and a syringe driver for agitating the contents of the syringe. More particularly the invention relates to an adapter connectable with a syringe pump and methods for delivery of an injectable liquid using such adapter. By connecting an adapter according to the invention to a syringe and a syringe pump, rotation of the syringe is achieved and homogeneity of the injectable is preserved. Particularly, the injectable liquid is an ultrasound contrast agent comprising an aqueous dispersion of gas-filled microbubbles or of particulate matter.