 Morphine in particular was used much more widely after the invention of the hypodermic syringe, and the practise of local anaesthesia by infiltration was another step forward in medicine resulting from the hypodermic needle, discovered at around the same time that it was determined that cocaine produced useful numbing of the mucous membranes and eye.A wide variety of drugs are injected.Among the most popular in many countries are morphine, heroin, cocaine, amphetamine, and methamphetamine.