Math Is Fun Forum

Jai Ganesh

Administrator

Registered: 2005-06-28

Posts: 53,302

Intramuscular Injection

Intramuscular Injection

Gist

Intramuscular (IM) injections deliver medication deep into muscle tissue for rapid systemic absorption, usually in volumes of 2–5 mL. Common sites include the deltoid (arm), vastus lateralis (thigh), and ventrogluteal (hip) muscles. Injections require a 90-degree angle, proper site identification, and sterile technique to avoid complications like pain, infection, or nerve damage.

Intramuscular (IM) injections deliver medicine deep into muscle tissue for fast absorption, used for vaccines (like flu shots, MMR), antibiotics, hormones (like Depo-Provera), emergency meds (epinephrine, glucagon), and antipsychotics, especially when oral intake is impossible or less effective, providing quicker action than oral routes or sustained release. Common sites include the thigh, upper arm (deltoid), and buttocks, chosen for adequate muscle and to avoid nerves/vessels, allowing for rapid systemic effect or controlled long-term release. 

Summary

Intramuscular injection (IM) is installing medications into the depth of specifically selected muscles. The bulky muscles have good vascularity, and therefore the injected drug quickly reaches the systemic circulation and thereafter into the specific region of action, bypassing the first-pass metabolism. It is one of the most common medical procedures to be performed annually.

Intramuscular injection (IM) is installing medications into the depth of specifically selected muscles. The bulky muscles have good vascularity, and therefore the injected drug quickly reaches the systemic circulation and thereafter into the specific region of action, bypassing the first-pass metabolism. It is one of the most common medical procedures to be performed annually. However, there is still a lack of adherence to recommended guidelines and an algorithm for giving IM among health professionals worldwide.

Drugs may be given intramuscularly both for prophylactic (around 5% for immunization) as well as curative purposes (accounting for more than 95% of IM injections).

The most common medications given by IM route include:

* Antibiotics- penicillin G benzathine penicillin, streptomycin
* Biologicals- immunoglobins, vaccines, and toxoids
* Hormonal agents- testosterone, medroxyprogesterone

Any nonirritant and soluble drugs may be given IM during an emergency scenario.

Details

Intramuscular injection, often abbreviated IM, is the injection of a substance into a muscle. In medicine, it is one of several methods for parenteral administration of medications. Intramuscular injection may be preferred because muscles have larger and more numerous blood vessels than subcutaneous tissue, leading to faster absorption than subcutaneous or intradermal injections. Medication administered via intramuscular injection is not subject to the first-pass metabolism effect which affects oral medications.

Common sites for intramuscular injections include the deltoid muscle of the upper arm and the gluteal muscle of the buttock. In infants, the vastus lateralis muscle of the thigh is commonly used. The injection site must be cleaned before administering the injection, and the injection is then administered in a fast, darting motion to decrease the discomfort to the individual. The volume to be injected in the muscle is usually limited to 2–5 milliliters, depending on injection site. A site with signs of infection or muscle atrophy should not be chosen. Intramuscular injections should not be used in people with myopathies or those with trouble clotting.

Intramuscular injections commonly result in pain, redness, and swelling or inflammation around the injection site. These side effects are generally mild and last no more than a few days at most. Rarely, nerves or blood vessels around the injection site can be damaged, resulting in severe pain or paralysis. If proper technique is not followed, intramuscular injections can result in localized infections such as abscesses and gangrene. While historically aspiration, or pulling back on the syringe before injection, was recommended to prevent inadvertent administration into a vein, it is no longer recommended for most injection sites by some countries.

Uses

Intramuscular injection is commonly used for medication administration. Medication administered in the muscle is generally quickly absorbed in the bloodstream, and avoids the first pass metabolism which occurs with oral administration. The medication may not be considered 100% bioavailable as it must still be absorbed from the muscle, which occurs over time. An intramuscular injection is less invasive than an intravenous injection and also generally takes less time, as the site of injection (a muscle versus a vein) is much larger. Medications administered in the muscle may also be administered as depot injections, which provide slow, continuous release of medicine over a longer period of time. Certain substances, including ketamine, may be injected intramuscularly for recreational purposes. Disadvantages of intramuscular administration include skill and technique required, pain from injection, anxiety or fear (especially in children), and difficulty in self-administration which limits its use in outpatient medicine.

Vaccines, especially inactivated vaccines, are commonly administered via intramuscular injection. However, it has been estimated that for every vaccine injected intramuscularly, 20 injections are given to administer drugs or other therapy. This can include medications such as antibiotics, immunoglobulin, and hormones such as testosterone and medroxyprogesterone. In a case of severe allergic reaction, or anaphylaxis, a person may use an epinephrine autoinjector to self-administer epinephrine into the muscle.

Contraindications

Because an intramuscular injection can be used to administer many types of medications, specific contraindications depend in large part on the medication being administered. Injections of medications are necessarily more invasive than other forms of administration such as by mouth or topical and require training to perform appropriately, without which complications can arise regardless of the medication being administered. For this reason, unless there are desired differences in rate of absorption, time to onset, or other pharmacokinetic parameters in the specific situation, a less invasive form of drug administration (usually by mouth) is preferred.

Intramuscular injections are generally avoided in people with low platelet count or clotting problems, to prevent harm due to potential damage to blood vessels during the injection. They are also not recommended in people who are in hypovolemic shock, or have myopathy or muscle atrophy, as these conditions may alter the absorption of the medication. The damage to the muscle caused by an intramuscular injections may interfere with the accuracy of certain cardiac tests for people with suspected myocardial infarction and for this reason other methods of administration are preferred in such instances. In people with an active myocardial infarction, the decrease in circulation may result in slower absorption from an IM injection.  Specific sites of administration may also be contraindicated if the desired injection site has an infection, swelling, or inflammation. Within a specific site of administration, the injection should not be given directly over irritation or redness, birthmarks or moles, or areas with scar tissue.

Risks and complications

As an injection necessitates piercing the skin, there is a risk of infection from bacteria or other organisms present in the environment or on the skin before the injection. This risk is minimized by using proper aseptic technique in preparing the injection and sanitizing the injection site before administration.  Intramuscular injections may also cause an abscess or gangrene at the injection site, depending on the specific medication and amount administered. There is also a risk of nerve or vascular injury if a nerve or blood vessel is inadvertently hit during injection. If single-use or sterilized equipment is not used, there is the risk of transmission of infectious disease between users, or to a practitioner who inadvertently injures themselves with a used needle, termed a needlestick injury.

Site-specific complications

Injections into the deltoid site in the arm can result in unintentional damage to the radial and axillary nerves. In rare cases when not performed properly, the injection may result in shoulder dysfunction. The most frequent complications of a deltoid injection include pain, redness, and inflammation around the injection site, which are almost always mild and last only a few days at most.

The dorsogluteal site of injection is associated with a higher risk of skin and tissue trauma, muscle fibrosis or contracture, hematoma, nerve palsy, paralysis, and infections such as abscesses and gangrene. Furthermore, injection in the gluteal muscle poses a risk for damage to the sciatic nerve, which may cause shooting pain or a sensation of burning. Sciatic nerve damage can also affect a person's ability to move their foot on the affected side, and other parts of the body controlled by the nerve. Damage to the sciatic nerve can be prevented by using the ventrogluteal site instead, and by selecting an appropriate size and length of needle for the injection.

Additional Information

An intramuscular injection is a technique for delivering medication deep into the muscles. This allows the medication to absorb quickly into the bloodstream.

You may have received an intramuscular injection at a doctor’s office the last time you got a vaccine, like the flu shot.

In some cases, a person may also self-administer an intramuscular injection. For example, certain drugs that treat multiple sclerosis or rheumatoid arthritis may require self-injection.

What are intramuscular injections used for?
Intramuscular injections are a common practice in modern medicine. They’re used to deliver drugs and vaccines. Several drugs and almost all injectable vaccines are delivered this way.

Intramuscular injections are used when other types of delivery methods are not recommended. These include:

oral (swallowed into the stomach)
intravenous (injected into the vein)
subcutaneous (injected into the fatty tissue just under the layer of skin)
Intramuscular injections may sometimes be used instead of intravenous injections because some drugs are irritating to veins or because a suitable vein cannot be located. However, not all intravenous medications can be administered intramuscularly.

They may be used instead of oral delivery because some drugs are destroyed by the digestive system when you swallow them.

Intramuscular injections are absorbed faster than subcutaneous injections. This is because muscle tissue has a greater blood supply than the tissue just under your skin. Muscle tissue can also hold a larger volume of medication than subcutaneous tissue.

Intramuscular injection sites

Intramuscular injections are often given in the following areas:

* Deltoid muscle of the arm

The deltoid muscle is the site most typically used for vaccines. However, this site is not common for self-injection because its small muscle mass limits the volume of medication that can be injected — typically no more than 1 milliliter.

It’s also challenging to use this site for self-injection. A caregiver, friend, or family member can assist with injections into this muscle.

To locate this site, feel for the bone (acromion process) located at the top of your upper arm. The correct area to give the injection is two finger widths below the acromion process. At the bottom of the two fingers will be an upside-down triangle. Give the injection in the center of the triangle.

Vastus lateralis muscle of the thigh

The thigh may be used when the other sites are not available or if you need to administer the medication on your own.

Divide the upper thigh into three equal parts. Locate the middle of these three sections.

Ventrogluteal muscle of the hip

The ventrogluteal muscle is the safest site for adults and children older than 7 months. It’s deep and not close to any major blood vessels or nerves. However, this site is difficult for self-injection and may require the help of a friend, family member, or caregiver.

Place the heel of your hand on the hip of the person receiving the injection, with your fingers pointing toward their head. Position your fingers so your thumb points toward their groin, and you feel the pelvis under your pinky finger. Spread your index and middle fingers in a slight V shape, and inject the needle into the middle of that V.

---

It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.