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2. the forcing of a liquid into a part, as into the subcutaneous tissues, the vascular tree, or an organ.
3. a substance so forced or administered; in pharmacy, a solution of a medicament suitable for injection.

Immunizing substances, or inoculations, are generally given by injection. Some medicines cannot be given by mouth because chemical action of the enzymes and digestive fluids would change or reduce their effectiveness, or because they would be removed from the body too quickly to have any effect. Occasionally a medication is injected so that it will act more quickly. In addition to the most common types of injections described below, injections are sometimes made into arteries, bone marrow, the spine, the sternum, the pleural space of the chest region, the peritoneal cavity, and joint spaces. In sudden heart failure, heart-stimulating drugs may be injected directly into the heart (intracardiac injection).
Sites for injections. A, subcutaneous injection sites. B, intramuscular injection site for children in the vastus lateralis muscle. C, D, and E, intramuscular injection sites for adults: C, deltoid muscle injection site. D, injection site in the buttock (dorsogluteal site). E, injection site in the anterolateral thigh (ventrogluteal site).
hypodermic injection subcutaneous injection.
intracutaneous injection intradermal injection.
intracytoplasmic sperm injection (ICSI) a micromanipulation technique used in male factor infertility; a single spermatocyte is inserted into an oocyte by micropuncture.
intradermal injection injection of small amounts of material into the corium or substance of the skin, done in diagnostic procedures and in administration of regional anesthetics, as well as in treatment procedures. In certain allergy tests, the allergen is injected intracutaneously. These injections are given in an area where the skin and hair are sparse, usually on the inner part of the forearm. A 25-gauge needle, about 1 cm long, is usually used and is inserted at a 10- to 15-degree angle to the skin.
intramuscular injection injection into the substance of a muscle, usually the muscle of the upper arm, thigh, or buttock. Intramuscular injections are given when the substance is to be absorbed quickly. They should be given with extreme care, especially in the buttock, because the sciatic nerve may be injured or a large blood vessel may be entered if the injection is not made correctly into the upper, outer quadrant of the buttock. The deltoid muscle at the shoulder is also used, but less commonly than the gluteus muscle of the buttock; care must be taken to insert the needle in the center, 2 cm below the acromion.

Injections into the anterolateral aspect of the thigh are considered the safest because there is less danger of damage to a major blood vessel or nerve. The area permits multiple injections, is more accessible, and is easier to stabilize, particularly in pediatric patients or others who are restless and uncooperative. The vastus lateralis muscle is located by identifying the trochanter and the side of the knee cap and then drawing a visual line between the two. The distance is then divided into thirds and the needle inserted into the area identified as the middle third.

The needle should be long enough to insure that the medication is injected deep into the muscle tissue. The gauge of the needle depends on the viscosity of the fluid being injected. As a general rule, not more than 5 ml is given in an intramuscular injection for an adult. The maximum for an infant is 0.5 ml, and the injection is made into the vastus lateralis muscle. The needle is inserted at a 90-degree angle to the skin. When the gluteus maximus muscle is the site chosen for the injection, the patient should be in a prone position with the toes turned in if possible. This position relaxes the muscle and makes the injection less painful.
intrathecal injection injection of a substance through the theca of the spinal cord into the subarachnoid space. Patients receiving intrathecal chemotherapy for metastatic malignancy of the central nervous system should maintain a flat or Trendelenburg position for one hour after treatment to achieve optimum distribution of the drug.
intravenous injection an injection made into a vein. Intravenous injections are used when rapid absorption is called for, when fluid cannot be taken by mouth, or when the substance to be administered is too irritating to be injected into the skin or muscles. In certain diagnostic tests and x-ray examinations a drug or dye may be administered intravenously. (See also intravenous infusion.)
jet injection injection of a drug in solution through the intact skin by an extremely fine jet of the solution under high pressure.
subcutaneous injection injection made into the subcutaneous tissues. Although usually fluid medications are injected, occasionally solid materials such as steroid hormones may be injected in small, slowly absorbed pellets to prolong their effect. Subcutaneous injections may be given wherever there is subcutaneous tissue, usually in the upper outer arm or thigh. A 25-gauge needle about 2 cm long is usually used, held at a 45-degree angle to the skin, and the amount injected should not exceed 2 ml in an adult. Subcutaneous insulin injections may be given at a 90-degree angle with an insulin syringe. Called also hypodermic injection.
Angle of needle insertion for administering a subcutaneous injection. From Lammon et al., 1995.
Z-track injection see z-track injection.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.


(in-jek'shon) [ inject]
1. The forcing of a fluid into a vessel, tissue, or cavity.

Patient care

All supplies used in preparing and administering an injection should be sterile. The caregiver chooses the appropriate syringe size for the volume of fluid to be injected, the appropriate needle gauge for the type of fluid, and the appropriate needle length for the administration route and site, considering the amount of muscle and adipose tissue, mobility limitations, and other site-related factors. Hands should be thoroughly cleansed before and after the procedure, and gloves worn if preparing a chemotherapeutic agent. The prescribed dose is accurately measured. An appropriate site is identified by using anatomical landmarks, and the area is cleansed with an antiseptic swab (from the center outward) and time allowed for the antiseptic to evaporate. The needle is inserted at the appropriate angle, given the prescribed route. Intradermal injections use a short fine needle with the opening faced upward; the needle is placed nearly parallel to the surface of the skin and advanced far enough for the injected fluid to make a small bubble under the skin, then carefully removed; pressure that could cause the fluid to leak out onto the skin surface should be avoided. Subcutaneous injections should consist of no more than 1 ml. A short needle should be inserted at a 45° angle, without aspiration, and gentle pressure or no pressure applied to the site after needle removal. After insertion into muscle (the needle is inserted directed into the muscle, at a 90° angle), the syringe plunger is aspirated to ensure that no blood returns to prevent accidental injection into a blood vessel. The prescribed medication is injected slowly, then the needle is removed, and pressure is applied to the site with a dry sponge. A Z-track method helps to ensure that the medication remains in the muscle as desired and does not leak back into subcutaneous tissues. When administering an intravenous (IV) injection, the syringe is aspirated and blood obtained to be certain the needle is in the vein. When removing a needle after administering an IV injection directly into the vein, the caregiver lessens the chance of bleeding into soft tissue by applying firm pressure with a dry sponge while elevating the site above the heart for several minutes. However, the vast majority of intravenous injections are administered through an IV catheter or an IV fluid port with a needle or needleless device. Pressure is not applied when removing this device. The needle should not be recapped; both the needle and syringe should be disposed in a “sharps” container according to protocol. The injection time and site, any untoward responses to the injection, desired effects, and adverse reactions to the particular drug injected are recorded.

2. A solution introduced in this manner.
3. The state of being injected; congestion.

depot injection

Parenteral administration of a long-acting medication or hormone.

dextrose and sodium chloride injection

A sterile solution of dextrose, salt, and water for use intravenously. It contains no antimicrobial agents.

epidural injection

The injection of anesthetic solution or other medicines into the epidural space of the spinal cord.

fractional injection

Injection of small amounts at a time until the total injection is complete.

hypodermic injection

An obsolete term originally meaning the injection of a substance beneath the skin. It is preferable to specify the route of administration, e.g., intramuscular, subcutaneous, intracutaneous, or intravenous.
See: local anesthesia

intra-alveolar injection

Introduction of anesthetic into the soft tissues adjacent to a tooth.

intracardial injection

Injection into the heart.

intracytoplasmic sperm injection

Abbreviation: ICSI
A commonly used assisted reproduction technique, in which spermatozoa, usually from a man with obstructive azoospermia or a low sperm count, are introduced directly into the ova of his partner. Some oocytes become fertilized and can then be transferred to the woman's uterus, where they mature.

intradermal injection

Injection into the skin, used in giving serums and vaccines when a local reaction is desired.
See: Intradermal Injections: Locating Sites and Administering

intralingual injection

The injection of medicines into the tongue, usually done as an emergency measure when a vein suitable for use is not available because of circulatory collapse.

intramuscular injection

Injection into intramuscular tissue, usually the anterior thigh, deltoid, or buttocks. Intramuscular injections are used primarily in the administration of vaccines, immune globulins, long-acting corticosteroids, some antibiotics, some hormones, analgesics, and sedatives. In shock, medications given intramuscularly may not be rapidly absorbed. No more than 4 ml should be injected at one time into an adult with normal musculature; in children and adults with underdeveloped musculature, no more than 2 ml should be injected at one time. Patients should be advised that intramuscular injections, e.g., for vaccination, are painful.


To avoid injury, newborn intramuscular injections should be administered in the middle third of the vastus lateralis muscle using a 5/8-in, 25-gauge needle.

intraosseous injection

Intraosseous infusion.

intraperitoneal injection

Injection into the peritoneal cavity.

intravenous injection

The injection into a vein or, more commonly, into an intravenous catheter of drugs, electrolytes, or fluids. The insertion of a needle directly into a vein (rarely necessary) requires a degree of skill that is easily obtained if proper instruction is obtained. The vein may be distended by applying a tourniquet with sufficient pressure to stop venous return but not arterial flow. The tourniquet is applied several inches above the injection site. If the patient does not have vascular collapse, the arterial pulse can be palpated; if not, the tourniquet is too tight. Heat applied to the area for 15 min before starting the injection will also help distend the vessels. The use of a needle attached to a 5- or 10-ml syringe will greatly facilitate controlling the course of the needle. It is best to insert the needle into the vein with the bevel side facing out and then, after the needle is in the vein, to rotate it so that the bevel is face in. There will be resistance as the needle goes through one side of the vein wall. The vein should be entered with the needle making only a narrow angle with the long axis of the vein. This will help to prevent pushing the needle completely through the vein. cutdown; intraosseous infusion;


Many liquid preparations are given by intravenous infusion. Those commonly used include isotonic saline, Ringer's lactate, dextrose 5% in sterile water, hyperalimentation fluids, lipids, vitamins, and numerous medications. The solution may be given continuously or by intermittent or bolus injection. The rate of infusion varies with the patient's needs.


Intravenous infusion usually is given through a vein in the hand or arm, but central veins or other peripheral veins may be used as indicated.


In patients with collapsed veins, it may be possible to make the veins apparent by placing a tourniquet around the arm or leg and then inserting a 23- or 25-gauge catheter into a tiny superficial vein. Instillation of sterile intravenous fluid into the vein while the catheter is in place will distend the entire larger vein proximal to the small vein. A larger needle or catheter can then be inserted into the larger vein.

iodinated I 131 albumin injection

A standardized preparation of albumin iodinated with the use of radioactive iodine, 131I.

iodipamide meglumine injection

A radiographic contrast medium combination of iodipamide and meglumine used to aid in x-ray examination of the gallbladder.

iodohippurate sodium I 131 injection

A radioactive contrast medium used in testing renal function.

iothalamate meglumine injection

A radiopaque contrast medium used in investigating arteries of the brain as well as in the rest of the body, and in studying kidney function.

iron dextran injection

A preparation of iron suitable for parenteral use.


Because of the risk of anaphylaxis, a test dose should be given before starting an infusion of iron.

jet injection

The injection of medicines and vaccines through the skin or intramuscularly without a needle. A nozzle ejects a fine spray of liquid at such speed as to penetrate but not harm the skin. The procedure is harmless and is esp. useful in immunizing a great number of persons quickly and economically.

lethal injection

A method of capital punishment by a combination of medications, typically, a sedative, a paralytic agent, an analgesic agent, and a fatal dose of potassium. Unlike other forms of execution (such as electrocution or the gas chamber), lethal injection is the only method that relies upon the direct participation of health care professionals. Some professional organizations (such as the American Medical Association) and several state boards with oversight over health care practic, have questioned whether the participation of health care professionals in lethal injection is appropriate, legal, or moral.

parathyroid injection

A standard preparation of the water-soluble parathyroid hormone. It increases the calcium content of the blood.

posterior pituitary injection

A standard preparation of the polypeptide hormones obtained from the posterior lobe of the pituitary body of healthy domestic animals.

protein hydrolysate injection

A sterile solution of amino acids and short-chain peptides. They represent the approximate nutritive equivalent of casein, lactalbumin, plasma, fibrin, or other suitable proteins from which the hydrolysate is derived by acid, enzymatic, or other method of hydrolysis. It may contain dextrose or other carbohydrates suitable for intravenous infusion. It is used intravenously in the treatment of hypoproteinemia in patients who are unable to eat or absorb food.

rectal injection

An instillation (not an injection) into the rectum; an enema.

sclerosing injection

The injection into a vessel or into a tissue of a substance that will bring about obliteration of the vessel or hardening of the tissues used, e.g., to manage esophageal varices or malignant pleural effusions.

selenomethionine Se 75 injection

Radioactive l-selenomethionine in which the sulfur atom in the methionine has been replaced by selenium. The compound is used intravenously to investigate methionine metabolism.

spinal injection

Introduction of fluids or medications into the spinal canal, i.e., the intrathecal space.
Enlarge picture

subcutaneous injection

Injection beneath the skin. Typical sites include the abdomen, upper or outer arm, and the thigh.
See: illustration

vaginal injection

A rare term for the instillation of fluid into the introitus; a douche.

vasopressin injection

A sterile solution of antidiuretic hormone.
Enlarge picture

Z-track injection

An injection technique in which the surface (skin and subcutaneous) tissues are pulled and held to one side before the needle is inserted deep into the muscle tissue in the identified site. The medication is injected slowly, followed by a 10-sec delay, at which time the needle is removed and the tissues are quickly permitted to resume their normal position. This provides a Z-shaped track, which makes it difficult for the injected drug to seep back into subcutaneous tissues.
See: illustration

intracytoplasmic sperm injection

Abbreviation: ICSI
A commonly used assisted reproduction technique, in which spermatozoa, usually from a man with obstructive azoospermia or a low sperm count, are introduced directly into the ova of his partner. Some oocytes become fertilized and can then be transferred to the woman's uterus, where they mature.
See also: injection
Medical Dictionary, © 2009 Farlex and Partners
References in periodicals archive ?
Could monopronucleated ICSI zygotes be considered for transfer?
could not find a relation between paternal obesity and pregnancy rates in ICSI cycles.13 In a recent meta analysis of 10 cohort studies involving 5262 male partners, paternal excess weight had no negative effects on CP and live birth rates and also sperm parameters in both IVF and ICSI cycles.22 The mechanism underlying the inability to link negative IVF results and increased BMI remains unclear.
From the 423 eligible ICSI families (215 with a male offspring and 208 with a female offspring), 303 (149 male and 154 female) could be reached.
In line with our previous studies (12) indicating the low efficiency of ICSI in sheep, the purpose of this study was to evaluate the influence of several strategies to improve male pronuclear formation and normal fertilization following ICSI in this species.
In this study, we wanted to assess mid-luteal estradiol (E2) levels in poor and good responders and compare its effect on the outcome of ICSI in our local population.
Thirty-four infertile couples in which the male partners had partial globozoospermia accepting IVF or ICSI treatment in our reproductive center from January 2009 to November 2013 were recruited as our subjects.
The percentage of fresh IVF cycles using ICSI increased from 36.4% to 76.2% during the study period.
Alkalinizing the urine to achieve a pH 7.5 (pH strips by DIRUI, Changchun, China) offered us the chance to retrieve some motile spermatozoa for a successful ICSI and most importantly the delivery of healthy twins.
Intracytoplasmic Sperm Injection (ICSI) has revolutionized the treatment of male infertility.
The interpretation of the report indicated that the cryopreserved samples of sperm would be suitable for ICSI.
Children born after IVF treatments with ICSI were at a 51 percent increased risk of mental disability, a rise from 62 cases to 93 cases per 100,000, it said.
"[This] creates a win-win situation," says Roberto Pieraccini, director of ICSI. "Both Microsoft and ICSI have among the best researchers in speech, so [this] collaboration ...