When you donate blood the needle goes into a large, visible vein in your arm or hand but when getting a shot the needle just goes somewhere in your arm.
In: Biology
Routes of drug administration: INJECTION
Subcutaneous route: The drug is injected in the adipose (fat) tissues right beneath the skin. The drug enters the bloodstream through small blood vessels (capillaries) or the lymphatic vessels. Protein drugs (ex. Insulin) are administered subcutaneously because oral administration results in destruction of the protein in the digestive tract.
Intramuscular route: The drug is injected into the muscles (upper arm, thigh or buttock) which lie below the skin and adipose (fat) tissues. It is usually used when larger volumes of drug products are needed. The absorption of the drug into blood depends on the blood supply to the muscle: higher the blood supply, quicker the absorption.
Intravenous route: The drug is directly administered into a vein. It is absorbed completely, and is best way to deliver a precise dose quickly and in a well-controlled manner. It is also used for administering irritating solutions that could damage the tissue if administered subcutaneously or intramuscularly. The drug effects last for a shorter period of time and may require frequent or continuous administration.
Intrathecal route: The drug is administered between two vertebrae in the lower spine and into the space around the spinal cord. The injection site is numbed using an anesthetic prior to drug administration. This route is used to produce rapid/local effects in the brain, spinal cord or meninges (layers of tissue that surrounds brain and spinal cord).
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