Intramuscular injections

Some medicines are given as an injection into a muscle if they can't be taken by mouth because the acids in your stomach affect the medicine. These medicines are better absorbed when given into a muscle, which means they work better.

Some other types of intramuscular medicines are called depot injections. They slowly release a slow-acting form of your medicine. The carrier liquid in the injection releases the medicine slowly so it lasts a lot longer in your body. 

Depot injections are usually given every few weeks or months, depending on the medicine. A depot injection might be a good option if you have difficulty swallowing medicine or remembering to take it regularly or if you prefer not to have to think about taking medicines every day.

Before you use an IM injection, make sure you have a discussion with your doctor about all the other medicines you are taking, including medicines you may buy from a health food store or over the counter.

IM injections may not be suitable for people who are taking some other types of medicines, or you may need to take special care. 

Some medicines given by IM injection are:

• antibiotics
• contraceptive hormones such as Depo-Provera
• vaccines
• EpiPen (adrenaline injections for severe allergic reactions)
• antipsychotics (read more about depot antipsychotics).

An IM injection is usually given into muscles such as your thigh, bottom or upper arm. Some medicines need to be given in larger muscles such as your bottom, while others can be given in smaller muscles such as your arm. Your healthcare provider will tell you which area is best for your medicine.

Some IM injections are available as pre-filled syringes, which means the syringe is already filled with medicine and is ready for use. Other IM injections come in a small glass bottle or vial, so the dose needs to be measured using a needle and syringe. Your healthcare provider will tell you what dose is best for you and show you how to measure your dose if you need to give the injection yourself at home.

Always wash your hands with soap and water and dry them before giving an IM injection.

• The skin at the injection site should also be clean before giving the injection.
• If your skin looks dirty, wash the area with soap and water and pat it try, or use an alcohol swab and allow it to dry.   
• If your skin doesn't look dirty, you don't need to clean it or use an alcohol swab before giving an injection. 

After most injections, it is recommended that you relax and limit your activity for the remainder of the day unless you have been told otherwise by your doctor or nurse.

• You may shower but avoid soaking baths, hot tubs, whirlpools or swimming pools for a few days. 
• You can exercise after having an IM injection, but it is a good idea to avoid strenuous exercise for several hours after the injection.

It is normal to get some pain and discomfort after an IM injection, but here are a few do's and don't to reduce the pain and discomfort.

Call your doctor if you get fever or chills or a lump, swelling, redness or bruising at an injection site that does not go away. This could be signs of an infection.

You must get rid of your used needles and syringes safely.

• Keep them out of reach of children and pets and places where they could hurt others. You can do this by buying a sharps container from your pharmacy.
• This is a special container made of hard plastic that has a tight-fitting lid so used needles and syringes can be stored securely.
• Don't flush used needles and syringes down the toilet or place them in household or public rubbish or recycle bins.
• Once your sharps container is full, take it to your pharmacy for safe disposal.
• Talk to your pharmacist about how you can get rid of your needles and syringes safely.

(Image credit: Healthify He Puna Waiora)