Major Routes of Parenteral Administration

The subcutaneous and intramuscular routes are the major routes of administration for the majority of sustained/controlled parenteral delivery systems, although the intravenous and peritoneal routes have also been used.

(1)    SUBCUTANEOUS
A dipose and connective tissues are poorly perfused with blood. This route is generally limited to non-irritating, water-soluble drugs that are well absorded, e.g., insulin. It is important that the injection site be rotated lbr chronically administered drugs to avoid local tissue damage and accumulation of unabsorbed drug. The volume of subcutaneous injection is usually restricted to 0.5-1.5 ml.

(2)    INTRAMUSCULAR
The best sites for intramuscular injection are the gluteal, deltoid and Vastus lateralis muscles it is important that the injection be deep in the muscle and away. From major nerves and arteries .To avoid tissue damage, the volume of intramuscular injection should Not exceed 2 ml .A polymeric membrane that is either impregnated with drug or Surrounds a drug reservoir can be used as the drug delivery device .a slightly Soluble from of from the drug can also serve as the drug source, there by generating desired constant rate of release. e.g. Butorphanol tartrate.

(3)    INTRAVENOUS
The intravenous rout is occasionally used as a route of administration for sustained/controlled dosage form such as liposomes, nanoparticle, erythrocytes, and polypeptides. When drug particles are injected intravenously, particle larger than about 1 micrometer are trapped in the lung, whereas particles with diameter between 0.1 and 7µm are trapped or take-up prelimary by the liver or the spleen. Only small particles with a diameter less than 0.1 µm accumulated in born marrow.

(4)    INTIRAPERITONEAL
Lymphatic channel are frequently the route by which tumor metastasize micro molecules administer intraperitoneally can gain access to the lymphatic system and return slowly to the vascular compartment. Thus, a macromolecule may be used a s a carrier to target Antineoplastic agents into the lymphatic system.
With subcutaneous and intramuscular injections, local trauma to the tissue occurs search time an injection is made. The trauma can be either chemicals due to puncture of tissue by needle and sudden distention of the tissue, or both. Thus, use of a sustained/controlled release dosage form which maintains therapeutic concentrations for a prolonged period of time is expected to produce greater tissue insult and injury. Therefore, irritating substance should be excluded form sustained/controlled-release parentral dosage forms.