How should a penicillin injection be given? A comprehensive guide

October 12, 2025 •

3 min read

Improper administration of a penicillin injection can lead to serious complications, including neurological or tissue damage if injected near a nerve or artery. Therefore, understanding the correct procedure is critical for patient safety. This guide details the essential steps for how should a penicillin injection be given, focusing on deep intramuscular administration techniques.

Quick Summary

Proper administration of a penicillin injection involves specific steps for preparation and technique, utilizing appropriate sites like the buttock or thigh based on patient age to ensure safe, deep intramuscular delivery.

Key Points

Deep Intramuscular Injection Only: Penicillin G benzathine, a common formulation, must be administered via deep intramuscular (IM) injection and never intravenously (IV) to prevent fatal reactions.
Choose the Correct Site: Select the injection site based on patient age and development. The buttock is suitable for adults, while the midlateral thigh is preferred for infants and small children.
Warm the Medication: For viscous suspensions like Bicillin L-A, warming the syringe to room temperature by rolling it between palms can significantly reduce injection pain.
Inject Slowly and Steadily: Administer the medication slowly over 20-30 seconds. This allows the muscle to accommodate the viscous suspension and prevents pain and needle blockage.
Monitor for Side Effects: Observe the patient for at least 15-30 minutes after the injection to ensure no immediate allergic reaction occurs, such as hives or swelling.
Avoid Nerves and Arteries: Careful landmarking of the injection site is necessary to avoid hitting major nerves (like the sciatic nerve) or blood vessels, which could cause permanent damage.

Understanding Penicillin Injection Types

Penicillin injections come in different formulations, affecting how they are prepared and administered. For example, Penicillin G benzathine, often known by brand names like Bicillin L-A, is a thick suspension designed for long-lasting effects. Other forms, such as aqueous Penicillin G potassium or sodium, are typically powders needing reconstitution for faster action. This article focuses on intramuscular (IM) administration, particularly for viscous benzathine formulations.

Pre-administration Preparation

Safe and effective administration requires careful preparation:

Verify the 'Five Rights': Confirm the right patient, medication, dose, route, and time against the order and patient information.
Inspect the Medication: Check the expiration date. For suspensions like Bicillin L-A, ensure the liquid is a uniform, opaque suspension without visible particles or discoloration.
Warm the Suspension (if applicable): Gently roll viscous suspensions between your palms to bring them to room temperature, which can help reduce injection pain. Do not freeze the medication.
Gather Supplies: Prepare a prefilled syringe or vial, diluent, an appropriate needle (usually 1.5 inches for adults), alcohol swabs, sterile gauze, and a bandage.

Choosing the Correct Injection Site

Selecting the right site is vital to avoid damaging nerves, blood vessels, or bone, and depends on the patient's age and muscle development.

Recommended Intramuscular Sites

For Adults:
- Dorsogluteal (Buttock): The upper, outer quadrant is a common deep IM site. It's located in the section below the hip bone to avoid the sciatic nerve.
- Ventrogluteal (Hip): Located on the hip, this site is often preferred for its safety due to fewer major nerves and vessels. Find it by placing your hand on the hip's greater trochanter, pointing your index finger towards the anterior superior iliac spine, and extending your middle finger towards the iliac crest. Inject in the 'V' formed by the fingers.
For Neonates, Infants, and Small Children (under 2 years):
- Midlateral Thigh (Vastus Lateralis): This is the preferred site due to better muscle development in this age group.
Site Rotation: For multiple doses, rotate injection sites to prevent muscle issues.


Injection Site	Age Group	Technique Notes	Advantages	Disadvantages
Dorsogluteal (Buttock)	Adults	Use upper-outer quadrant; prone with toes inward relaxes muscle.	Large muscle mass, good for viscous medications.	Risk of sciatic nerve damage if improperly located.
Ventrogluteal (Hip)	Adults and Older Children	Find the 'V' on the hip using landmarks; patient can be prone or supine.	Safest site, avoids major nerves/vessels.	Landmark identification can be challenging for some.
Midlateral Thigh	Neonates, Infants, Small Children	Patient lying down; inject into the middle third of the outer thigh.	Safe for younger patients with developing muscles.	Smaller muscle volume; needs careful landmarking.

Step-by-Step Injection Procedure

Hand Hygiene and Patient Position: Wash hands and use PPE if needed. Position the patient to relax the muscle, such as lying prone with toes inward for a buttock injection.
Clean the Site: Clean the area with an alcohol swab, moving outwards in a circle. Let it air dry.
Prepare the Skin: Pull the skin taut. The Z-track method, displacing the skin before injection, can prevent medication leakage into subcutaneous tissue, especially for viscous injections.
Insert the Needle: Insert the needle deep into the muscle at a 90-degree angle with a quick, smooth motion.
Aspirate: Gently pull back the plunger. If blood is visible, withdraw the needle, discard the syringe, and prepare a new injection at a different location. (Aspiration may be omitted in some modern guidelines for specific medications, but is generally advised for penicillin IM injections).
Inject Slowly: Administer the medication slowly over 20 to 30 seconds. This slow rate helps the muscle absorb the medication and minimizes pain, particularly for thick penicillin suspensions.
Withdraw and Apply Pressure: After injection, release the skin (if using Z-track), withdraw the needle at the same angle, and apply firm pressure with sterile gauze.
Bandage: Apply a bandage. Avoid rubbing the injection site.

Post-Injection Monitoring and Conclusion

Monitor the patient for at least 15 to 30 minutes post-injection for allergic reactions, which can range from mild rashes to severe anaphylaxis. Advise patients to report serious symptoms like difficulty breathing or swelling. Patients treated for syphilis should also be aware of the potential for a Jarisch-Herxheimer reaction (fever, chills) within the first day.

Administering a penicillin injection safely and effectively requires meticulous attention to preparation, technique, site selection, and post-injection monitoring. Following established guidelines helps prevent complications and ensures positive patient outcomes.

Penicillin information from Pfizer Medical

Frequently Asked Questions

Intramuscular (IM) penicillin is injected directly into the muscle and is the correct route for most penicillin suspensions, like Bicillin L-A. Intravenous (IV) administration involves injection into a vein and is strictly prohibited for certain penicillin formulations, as it can cause serious, even fatal, side effects.

Penicillin injections should typically be administered by a trained healthcare professional, such as a nurse or doctor, to ensure correct technique and proper handling of potential side effects. While some patients may be trained for self-injection, it is not common for penicillin.

Pain can be reduced by warming the medication to room temperature before administration and injecting it slowly and steadily over 20 to 30 seconds. Some formulations may also contain a local anesthetic like procaine to lessen pain.

For adults, the upper-outer quadrant of the buttock (dorsogluteal) or the ventrogluteal (hip) site are used. For neonates, infants, and small children, the midlateral aspect of the thigh is the preferred injection site.

It is recommended to observe the patient for 15 to 30 minutes after the injection. This is a crucial step for monitoring and managing any immediate side effects or allergic reactions.

The Z-track technique involves displacing the skin laterally before injection. It is used to prevent medication, particularly viscous or irritating substances, from leaking back into the subcutaneous tissue after the needle is withdrawn.

For repeated injections, the injection site should be rotated to prevent tissue damage. For example, alternating between the left and right buttock is a common practice.