The main feature of the intravenous route of administration is the absence of all the steps described in the other routes of administration (oral, subcutaneous, intramuscular, etc.).
Administration routes
- enteral
- Oral
- Sublingual
- Rectal
- parenteral
- Intravenous
- Intramuscular
- subcutaneous
- INHALATION
- TRANSCUTANEOUS
With intravenous administration, in fact, the active ingredient, solubilized in an aqueous vehicle, is directly introduced into the circulatory system. This means that if we inject a certain dose of active ingredient, contained in a specific pharmaceutical form, the whole dose administered arrives unscathed in the blood, without undergoing any modification. We can therefore say that the bioavailability of the intravenous route is 100%; in fact the ratio between the dose administered and the dose used is equal to 1.
Intravenous administration is practiced only by highly specialized personnel and is very useful for:
- all those types of drugs that can cause tissue irritation;
- low THERAPEUTIC INDEX drugs;
- drugs that are rapidly metabolized before or during absorption (such as peptides that are digested in the stomach like any other protein);
- it also allows the introduction of high volumes of liquids (phleboclysis);
- it is used for emergency therapy (eg convulsions, asthmatic attacks, cardiac arrhythmias, hypertensive crisis, anaphylactic shock).
The intravenous injection must be carried out very slowly, so as not to cause sudden changes in pressure inside the blood vessel. The solutions that are injected must be apyrogenic and isotonic with blood. Consequently, they must be neither hypotonic (they would cause hemolysis of red blood cells), nor hypertonic (they would cause the formation of aggregates of red blood cells, therefore possible thrombus); moreover they must not present substances that induce the precipitation of blood components and must not be composed of oily solvents (however oil-in-water emulsions are allowed). You can administer up to 20 ml in bolus, or over 50 ml by slow infusion.
The negative aspects of the intravenous route of administration are:
- possibility of emboli formation;
- possibility of finding bacterial and viral infections;
- possibility of induction of bradycardia, hypotension and fainting.
