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Intravenous (I.V.) drugs are drugs that are injected directly into a blood vessel. These drugs may be introduced into the circulatory system either with a syringe or an intravenous catheter that is connected to a bag of medication by use of a tube. Doctors may choose this route to administer medications because it is the fastest method of delivering drugs into the body.
Medications may be given in various ways. Topical medications are those applied to the skin on a desired area of the body. Enteral medications are absorbed through the intestinal tract, as in a tablet or capsule. Parenteral drugs are those given by means other than the digestive tract, such as intravenous or intramuscular injection.
A straightforward way of administering intravenous drugs is by using a syringe. Usually, a tourniquet is applied to the arm, either above the elbow or the wrist depending on what vein is to be used. When the vein is distended, the needle is gently inserted, and the syringe plunger is pulled back to verify the placement of the needle in the vein. If blood is aspirated into the syringe, the needle is in the correct place. The tourniquet is then removed and the drug may be injected.
Another way of administering intravenous drugs is by using an I.V. cannula. The cannula is a very narrow tube that usually contains a needle called a trocar, which is used to puncture the vein. The needle is withdrawn after the cannula is pushed into place. The cannula is then secured in place so that the intravenous drugs can be administered.
I.V. tubing may be attached to the cannula so that fluids, medications, or blood may flow directly into the patient's bloodstream. This allows the intravenous drugs to be immediately introduced into the body. These medications may be mixed into the main I.V. solution bag or introduced by a secondary line.
I.V. administration is the preferred method for some, but not all, medications. For those drugs requiring a consistent therapeutic level within the body, I.V. is the most efficient and accurate route. If a particular medication tends to be broken down by digestive enzymes, is irritating when injected into muscle or subcutaneous tissue, or is poorly absorbed by other routes, I.V. administration may be considered.
Intravenous drugs may also be given through a central venous catheter that is inserted directly into one of the major veins of the heart. This means of administration may be reserved for medications that need to be quickly distributed throughout the body, or for drugs that may irritate smaller veins. The risk of bleeding and infection are high with this type of I.V., and care should be taken to monitor the patient carefully.
One of the reasons this is the fastest method of delivering drugs to your body (besides the fact that enters straight into your bloodstream) is it bypasses metabolism in the liver, basically meaning a stronger effect will be felt from the same amount of drug if administered orally. That's why drugs like diazepam (Valium) which are typically taken as tablets are injected in emergency situations to quickly stop a seizure. As an epileptic I know personally that it's saved many lives.