Intramuscular antibiotics: a comprehensive guide to understanding, using, and mastering this method of administration

What is an intramuscular antibiotic?

Intramuscular antibiotics are medications administered by injection directly into the muscle, allowing for rapid and effective diffusion of the active ingredient into the body. Unlike the oral route, this method of administration is used when rapid efficacy is desired or when oral intake is impossible (vomiting, digestive disorders, emergency, etc.).

This route is particularly appreciated in emergency medicine or pediatrics. It bypasses certain problems related to digestive absorption or patient cooperation.

Principles of Intramuscular Administration

Intramuscular injection involves introducing the antibiotic into the deep muscle tissue, where it will be rapidly absorbed by the blood vessels. This method of administration requires a good knowledge of anatomy to avoid complications such as nerve or vascular damage.

Common injection sites include the gluteal muscle (buttocks), thigh (vastus lateralis), and sometimes the deltoid muscle (shoulder), depending on the patient's age, the amount of medication to be injected, and the viscosity of the product.

Administration must adhere to strict aseptic rules to avoid any risk of local infection or abscess.

Main indications for intramuscular antibiotics

The indications for an intramuscular antibiotic are varied and depend on the clinical situation:

• Acute infections requiring rapid treatment (e.g., bacterial meningitis, early-stage septicemia, soft tissue infection).
• Patients unable to take oral medication (children, unconscious patients, severe digestive disorders).
• Induction or relay treatments after perfusion.
• Infectious diseases with a high risk of complications (gonorrhea, syphilis, etc.).

In some cases, the intramuscular route is preferred for its effectiveness, speed, and adherence to the dosage regimen, especially when treatment adherence is difficult.

The main antibiotics administered intramuscularly

Among the families of antibiotics frequently injected intramuscularly are:

• Penicillins (e.g., Benzathine benzylpenicillin, used for syphilis or prophylaxis of acute rheumatic fever)
• Cephalosporins (e.g., Ceftriaxone, used in severe infections or as a follow-up to intravenous administration)
• Aminosides (e.g. Gentamicin, Amikacin for certain severe infections)
• Macrolides (less frequent, but possible in specific contexts)
• Other: Certain veterinary or hospital specialties may be administered intramuscularly (IM) for bioavailability or safety reasons.

It should be noted that not all antibiotics are suitable for this route. The choice depends on the pharmacokinetic and pharmacodynamic characteristics of each molecule.

Advantages and disadvantages of the intramuscular route

Advantages:

• Speed of action: The antibiotic rapidly enters the bloodstream, ideal for emergency situations.
• Avoids digestive passage: Practical in case of vomiting, malabsorption, or when oral intake is impossible.
• Spaced doses: Some antibiotics can be administered in a single or spaced dose, which promotes adherence.

Disadvantages:

• Pain at the injection site: Intramuscular injection can be painful, especially for large volumes or viscous solutions.
• Local risks: Hematoma, abscess, infection, nerve or vascular lesion.
• Requires trained personnel: Administration is not possible in self-medication.
• Less suitable for long treatments: Risk of local toxicity and poor long-term tolerance.

Administration procedure and precautions

Intramuscular injection of an antibiotic must follow a strict procedure to limit risks:

1. Choice of injection site adapted to age and drug volume.
2. Rigorous asepsis: Disinfection of the site, sterile equipment.
3. Aspiration before injecting to ensure that no blood vessel is touched.
4. Slow injection to limit pain and allow better diffusion of the product.
5. Post-injection monitoring: Monitor for local signs (pain, redness, swelling) or general signs (allergy, anaphylactic shock).

Some additional precautions should be taken with the elderly, children, or patients with coagulation disorders.

Possible complications and side effects

Like any medical procedure, the intramuscular injection of an antibiotic carries risks:

• Allergic reactions: The onset of anaphylactic shock requires emergency management.
• Local effects: Pain, inflammation, necrosis, abscess.
• Nerve injury: Rare, but possible if the injection site is not respected.
• Hematoma: In patients on anticoagulants or with coagulation disorders.

It is therefore essential to inform the patient of the risks and to monitor the evolution after the injection.

Role of intramuscular antibiotics in modern medical practice

The intramuscular route remains a valuable tool, especially in emergency contexts or when oral treatment is not possible. However, the evolution of oral molecules and outpatient infusions tends to reduce its use outside of specific situations.

In pediatrics, it is still used for certain pathologies, as well as in prophylaxis for specific diseases such as syphilis or acute rheumatic fever.

Best practices and recommendations

To optimize the effectiveness and safety of intramuscular antibiotics:

• Respect the indications and do not use this route without valid reason.
• Train healthcare providers in injection technique and complication management.
• Inform the patient about the nature of the treatment, the benefits, and the risks.
• Consider official recommendations (HAS, WHO, learned societies) and local protocols.

Conclusion

Intramuscular antibiotics remain an essential tool in certain medical situations, allowing for rapid and effective management of severe infections. However, it must be used with discernment, in compliance with the indications and rules of good practice, in order to avoid complications and ensure the best possible patient management.

‍