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Injections are parenteral therapy. It means giving of therapeutic agents including food outside the alimentary tract.

An injection is the forcing of a fluid into a cavity, a blood vessel or body tissue through a hollow tube or needle


  • To get a rapid and systemic effect of the drug
  • To provide the needed effect even when the patient is unconscious
  • Assures that the total dosage will be administered and the same will be absorbed for the systemic action of the drug
  • Provides the only means of administration for medications that cannot be given orally
  • To obtain a local effect at the sight of the injection
  • To restore blood volume by replacing the fluid, e.g. in shock conditions
  • To give nourishment when it cannot be taken by

Types of Injections

  • Intradermal: drug introduced into the dermis
  • Subcutaneous: drug introduced into the subcutaneous tissue
  • Intramuscular: injected into the muscles
  • Intravenous: introduced into the vein
  • Intraspinal: introduced into the spinal cavity
  • Intra-osseous: introduced into the peritoneal cavity
  • Venesection: opening a vein and introducing a tube or wide bore needle and introducing medicines an fluids or taking out blood
  • Infusions: when a large quantity of medicines as fluids are to be introduced into the body
  • Transfusions: it is the introduction of whole blood or plasma into a vein or artery

Factors that Favors Absorption

  • Blood supply to the area: fluids injected into the blood stream will act quicker than any other methods used
  • The composition of the fluid injected: solubility and diffusibility of the fluid
  • Application of heat: heat dilates the blood vessels; therefore the heat applied over the site of injection increases the rate of absorption
  • Massage: it stimulates the local blood supply and increases the rate of absorption
  • Circulation time of the blood: absorption of medicines and fluids injected to the body will diminished in a person who has venous congestion (edema)
  • Physical condition: the local disease condition of the skin and underlying tissues such as skin lesions, inflammations, etc. delays the absorption of the drug
  • Addition of the substances: that tends to breakdown the natural resistance of the tissues can increase the rate of absorption

Complication of Injections

  • Allergic reactions for certain drugs, e.g. penicillin
  • Infections (abscess formation)
  • Pyrogenic reactions (producing fever)
  • Tissue trauma
  • Psychic trauma
  • Pain
  • Accidental intravascular injections
  • Foot drop and persistent paralysis of the limb
  • Air embolism
  • Over dose and under dose of the medication
  • Errors in the administration of the medications
  • Infectious hepatitis
  • Circulatory overload
INJECTIONS - Purpose, Types, Factors, Complications
INJECTIONS – Purpose, Types, Factors, Complications
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