Injection (medicine)

[1] An injection is considered a form of parenteral drug administration; it does not involve absorption in the digestive tract.

Injections are among the most common health care procedures, with at least 16 billion administered in developing and transitional countries each year.

[2] Of these, 95% are used in curative care or as treatment for a condition, 3% are to provide immunizations/vaccinations, and the rest are used for other purposes, including blood transfusions.

Injections generally administer a medication as a bolus (or one-time) dose, but can also be used for continuous drug administration.

Rarely, more serious side effects including gangrene, sepsis, and nerve damage may occur.

If needles or syringes are reused between people, or if an accidental needlestick occurs, there is a risk of transmission of bloodborne diseases such as HIV and hepatitis.

Used needles should ideally be placed in a purpose-made sharps container which is safe and resistant to puncture.

All injections are considered forms of parenteral administration, which avoids the first pass metabolism which would potentially affect a medication absorbed through the gastrointestinal tract.

Systemic injections may be used when a person cannot take medicine by mouth, or when the medication itself would not be absorbed into circulation from the gastrointestinal tract.

Medications administered via a systemic injection will enter into blood circulation, either directly or indirectly, and thus will have an effect on the entire body.

Intravenous injections, abbreviated as IV, involve inserting a needle into a vein, allowing a substance to be delivered directly into the bloodstream.

[4] An intravenous injection provides the quickest onset of the desired effects because the substance immediately enters the blood, and is quickly circulated to the rest of the body.

[7][8] Intramuscular injections, abbreviated as IM, deliver a substance deep into a muscle, where they are quickly absorbed by the blood vessels into systemic circulation.

[17] With the exception of occasional differences in the accuracy of blood tests when drawn from an intraosseous line, it is considered to be equivalent in efficacy to IV access.

These injections can range from a one-time dose of a steroid to help with pain and inflammation to complete replacement of the synovial fluid with a compound such as hyaluronic acid.

[22] Hyaluronic acid injection is used to supplement the body's natural synovial fluid and decrease the friction and stiffness of the joint.

[29] Various materials can be used to manufacture implants including biodegradable polymers, osmotic release systems, and small spheres which dissolve in the body.

Pain may be dampened by prior application of ice or topical anesthetic, or pinching of the skin while giving the injection.

Some studies also suggest that forced coughing during an injection stimulates a transient rise in blood pressure which inhibits the perception of pain.

[16]: 358, 373 Injections into the skin and soft tissue generally do not cause any permanent damage, and the puncture heals within a few days.

Intravenous and intramuscular injections may cause damage to a nerve, leading to palsy or paralysis.

[44] The most basic reuse prevention device is an "auto-disable" plunger, which once pressed past a certain point will no longer retract.

A sharps container which is 3⁄4 filled should be sealed properly to prevent re-opening or accidental opening during transportation.

[51] As of 2024, at least ten countries currently offer safe injection sites, including Australia, Canada, the United States, Denmark, France, Germany, Luxembourg, The Netherlands, Norway, Spain and Switzerland.

Common substances present in snake venom include neurotoxins, toxic proteins, and cytotoxic enzymes.

[55] Sting rays use their spinal blade to inject a protein-based venom which causes localized cell death but is not generally life-threatening.

Bees use a stinger located in their hind region to inject a venom consisting of proteins such as melittin, which causes a localized painful and itching reaction.

[57] Leeches can inject an anticoagulant peptide called hirudin after attaching to prevent blood from clotting during feeding.

This property of leeches has been used historically as a natural form of anticoagulation therapy, as well as for the use of bloodletting as a treatment for various ailments.

[63] While some plants have thorns, spines, and prickles, these generally are not used for injection of any substance, but instead it is the act of piercing the skin which causes them to be a deterrent.