ABSTRACT
The parenteral routes of drug administration to achieve extended action are: intramuscular, subcutaneous, intraperitoneal and interarticular. Continuous intravenous infusion after attaining a steady state provides for maintenance of drug plasma level equilibrium over the entire period of infusion, provided that the administered amount of drug equals the amount eliminated from the body. The same can be achieved by subcutaneous infusion. Absorption rate can be limited by the release rate from the dosage form. Most of the drugs given parenterally in aqueous solutions produce their therapeutic effect quite rapidly. After intravenous injection of a drug solution, the onset of action may occur within seconds, and after subcutaneous or intramuscular injection, it may occur within minutes. Atropine sulfate solution causes maximum pulse rate elevation after intravenous injection within 7 min, and after intramuscular injection, within 40 min. Necrotic muscle tissue adsorbs less drug and more slowly than undamaged tissue.
