The discovery of the intravenous route of administration through hypodermic syringe in the nineteenth century was a revolutionary development in the medical field. Today it is a routine practice in hospitals.

1. The intravenous route ensures rapid action when compared with other routes of administration and may be lifesaving in emergency situations because the drug is administered directly into the blood circulation.
2. The veins of the antecubital area (in front of the elbow) are usually selected for direct intravenous injection.
3. Strict aseptic precautions must be maintained to avoid risk of infection.
4. The injectable solutions, syringes and needles must be sterilized and the point of administration must be disinfected to prevent the entry of bacteria from the skin into the blood through the needle.
5. Both small and large volume parenterals can be administered by the intravenous route.
6. Intravenous preparations must be aqueous in nature. They should mix with the circulating blood and should not precipitate from the solution.
7. Solutions containing nutrients, plasma volume expanders, electrolytes, amino acids and therapeutic agents are administered with a needle or catheter by continuous infusion.
8. According to the needs of the patient, the infusion or flow rate can be adjusted. In general, the flow rate for intravenous fluids is expressed in milliliters per hour and it ranges from 42 ml/h to 150 ml/h.

However, the disadvantages of this route are as follows:

1. In case of an adverse reaction, the drug cannot be easily removed from circulation.
2. Special care must be taken to prevent overdosing or underdosing.
3. Thrombus and embolus formation may be induced by needles and catheters.
4. The parenteral solutions should be sterile and free from particulate matter.