There exists three types of injections: intramuscular, subcutaneous and intradermal. The intramuscular injection is preferred over the other two types because it seems to be the best tolerated type.
Although the intramuscular injection is the easiest to administer, it is important to follow some basic rules: the length of the needle must be in interval 20 to 22 gauge and the maximum amount of remedy is 5 ml/injection.
Subcutaneous injections are recommended for medicines that require slower absorption rates than in the case of intramuscular injections. By this method, substances that do not irritate the body tissues, are administered in adipose tissues.
For example, insulin and some vaccines are given subcutaneously. The length of the needle used must be between 23 to 25 gauge and the volume of remedy administered is no larger than 1ml.
Intradermal injections are used for tuberculin and allergy testings. This type of injection usually places a small amount of allergen or antigen under the skin. The sting is made right under the surface of the skin, between its layers.
Reasons why intramuscular injections are used more frequently and preferred over other injections is mainly due to the fact that through an intramuscular injection you can put the medicine deep into the muscle tissue, allowing it to be quickly absorbed into the bloodstream. The reason for this is," because the muscle tissue has a greater blood supply than the area just under the skin." Injections given just under the skin are called subcutaneous injections. Muscle tissue also tends to be able to hold more medication than tissue just below the skin.
Intramuscular injections may also be used over IV's because certain drugs can be very bothersome to veins causing them to become irritated and will make the person receiving the drugs feel uncomfortable. It can also be difficult to find a vein so intramuscular injections are a good choice.
The reason intramuscular injections might also be preferred over swallowing drugs is that certain drugs can be destroyed by the digestive system and therefore become useless.