The invention relates to percutaneous administration of drugs and vaccines in form of solid penetrating needles, “injectable needles”, comprising a polymeric matrix resulting from the polymerization of a polymerizable paste or mixture. The injectable needles are hard enough to penetrate the skin and can be administered percutaneously by simple pusher or injector delivery devices. The manufacturing procedure of the injectable needles allows for the incorporation of the drug as preformulated stable microparticles and incorporation of modifying agents to modulate stiffness, solubility and drug release. Drugs formulated in these injectable needles offer a safe, simple and effective alternative to conventional percutaneous drug delivery systems based on hypodermic needles and syringes that require refrigerated storage and reconstitution prior to administration.