Abstract: A generally pen-like syringe incorporates a dose metering device provided by a cap 7 rotatable with respect to a pen body 8 to a position related to the dose of medicament (for example insulin) to be injected. The rotation compresses a coil spring 6, which is prevented from unwinding by cooperating ratchet teeth. When the dose is to be injected, a trigger slide 42 is moved to the left causing the ratchet teeth to come out of engagement. This permits the spring 6 to unwind, thereby rotating a drive sleeve 1, drive gear 3 and a drive plunger 2. The drive plunger 2 is formed with a quick pitch screw thread so that its rotational movement is accompanied by axial movement to cause medicament to be discharged from a cartridge and injected through a needle.