When a medication is injected directly into muscle, it is called an intramuscular injection (IM). The Z-track method of IM is used to prevent tracking (leakage) of the medication into the subcutaneous tissue (underneath the skin).
During the procedure, skin and tissue are pulled and held firmly while a long needle is inserted into the muscle. After the medication is injected, the skin and tissue are released. The needle track that forms during this procedure takes the shape of the letter “Z,” which gives the procedure its name. This zigzag track line is what prevents medication from leaking from the muscle into surrounding tissue.
The procedure is usually administered by a nurse or doctor. In some cases, you may be instructed in how to perform Z-track injections on yourself at home.
Side effects can include swelling and injection discomfort. Z-track injection is usually less painful than a traditional IM injection.
The Z-track method is particularly useful with medication that must be absorbed by muscle to work, or when using a dark-colored drug that can cause staining of the skin. It also helps to prevent medication from seeping into the subcutaneous tissue and ensures a full dosage. It is less likely that you will develop injection site discoloration or lesions. Z-track injection may be less painful than a traditional IM injection.
It is important that the correct size needle is used. Your healthcare team may take your weight, build, and age into consideration. You may also be asked about preexisting conditions. Be sure to tell your doctor if you have a bleeding disorder.
Your healthcare provider, usually a nurse, will choose the best site for your injection (usually the buttocks or legs), and position you so that your muscle is as relaxed as possible. You may be asked to lie down, stand, or sit.
The medication and dosage will be checked for accuracy.
Your nurse will clean the injection site to minimize the possibility of infection.
If you are nervous or tense, try to relax by taking slow, deep breaths.
Using one hand to pull downward on your skin and subcutaneous tissue, your nurse will hold it firmly about an inch away (2.54 cm) from the muscle. The needle will be held at a 90-degree angle in the other hand. The needle will be quickly inserted deeply enough to penetrate your muscle.
Next, the nurse will pull back the plunger and check the syringe for evidence of aspirated blood. If blood is present, it means a vein may have been nicked, so a new site must be used. This will involve a new needle and fresh medication.
If there is no blood in the syringe, the medication will be slowly injected directly into the muscle. The needle will remain in place for about 10 seconds before it is withdrawn.
When the skin and tissue are released, the needle track is broken, briefly forming a shape like the letter “Z.”
Your nurse may apply gentle pressure to the site for a few moments. A small bandage may be used.
Note: Never massage the site of your Z-track injection. This may cause the medication to leak. It may also cause irritation.
Z-track injection is generally considered a common and safe procedure. Mild side effects include swelling, site pain, and bruising. Less common risks include:
- formation of abscess
- damage to tissues, nerves, blood vessels, or bones
- hemorrhage, especially in people with bleeding disorders