Intramuscular vs Subcutaneous Injections - Which is Better? Imagine you’re sitting next to two sick people in a doctor’s office. One person is given an injection and they recover quickly, the other is also given an injection but it takes longer for the medication to kick in. Why does one recover fast and the other more slowly? This is because they may have been given two different types of injections!

The person who recovered quickly was most likely given an intramuscular injection. An intramuscular injection is the injection of a substance/medication which is delivered deep into the muscles. This method of drug administration allows the substance to be absorbed into the bloodstream quickly1. Vaccines are a common example of a substance that is given to patients via intramuscular injection.

In comparison, the person who recovered more slowly was most likely given a subcutaneous injection is the injection of a substance/medication into the tissue layer between the skin and muscle. This type of injection uses a short needle and the substance/medication is absorbed more slowly in the bloodstream2

What are the advantages and disadvantages of Intramuscular Injections?

Advantages DisadvantagesIntramuscular injections are often better than intravenous injections as some drugs may irritate veins and suitable veins may be difficult to locate in some patients3 – this is particularly seen in elderly patients!

Intramuscular injections can be used instead of oral drugs as drugs taken orally can be destroyed by the digestive system, whereas an intramuscular injection is simply delivered straight into the muscle

Hate seeing the doctor? Not a problem! drug dosage can be easily controlled and simple to use so patients can administer intramuscular injections on their own

This type of injection is absorbed much faster than subcutaneous injections as muscle tissue has a greater blood supply than the tissue just under the skin

Can be quite painful! Some side effects include numbness, redness, swelling, persistent bleeding and allergic reactions

If the injection is given incorrectly, nerve damage might occur4 (As if injections weren’t painful enough!)

Administering intramuscular injections at the wrong site can lead to wastage of the medication/drug – this means the drug might be useless!

If the dose given is too large, there may be side effects, but if the dose given is too low, there may be no effect or pain relief! So, it is important to get the correct dose!

What are the advantages and disadvantages of Subcutaneous Injections?

Advantages DisadvantagesDid you know this type of injection can be self-administered by the patient? Meaning it is simple to use and super convenient

It is also less expensive and less painful than intramuscular injections

Lower risk of developing an infection and patient compliance is a lot higher with this type of injection

There is almost complete absorption of the drug in the patient, so an accurate measure of the amount of drug absorbed is possible5

Many injection sites are available for multiple dosing if required

Only small volumes of drug can be administered (<1 – 2ml)

There can also be degradation of therapeutic at the injection site

If the drug is confined at the injection site, some patients can get adverse reactions at the site of the injection6

The speed of absorption is slower when compared to intramuscular injections

Are Intramuscular injections really that helpful? – YES! and here ’ s why: Combating Schizophrenia

Aripiprazole is an atypical antipsychotic prescription medication given via intramuscular injection to treat Schizophrenia in adults7. This drug is long-acting and decreases hallucinations and extreme changes in mood as well as improving concentration and clarity in schizophrenic patients.

Aripiprazole is injected into the gluteal muscle once a month at a dose of 400mg and is metabolised mainly through pathways involving CYP 450, CYP2D6 and CYP3A4 enzymes8

However, there are some side effects of this drug which include dizziness, light-headedness, drowsiness, blurred vision, weight gain, tremors and swelling/pain at the site of injection9. More severe side effects include increased risk of death in elderly patients with a dementia-related psychosis, Neuroleptic Malignant Syndrome (NMS), tardive dyskinesia and hyperglycaemia

When in need, Epinephrine has speed!Epinephrine is a common drug used in emergencies to treat serious allergic reactions! This drug can be injected via intramuscular injection to quickly improve breathing, blood pressure and stimulate the heart10. The effects of Epinephrine are rapid but is not intended to be a long-lasting form of medication as the effects of this drug last for only 10 to 20 minutes.

Side effects of this drug include vomiting, dizziness, nausea, headaches, sweating, anxiety and difficulties with breathing11.

References1. Healthline 2017, What are Intramuscular Injections?, viewed 4 May 2018,

<https://www.healthline.com/health/intramuscular-injection#helpful-tips>

2. Healthline 2017, What is a Subcutaneous Injection?, viewed 4 May 2018,

<https://www.healthline.com/health/subcutaneous-injection>

3. ConnectUS The Global Issues Blog 2015, 5 Advantages and Disadvantages of Intramuscular Injections,

viewed 4 May 2018, <https://connectusfund.org/5-advantages-and-disadvantages-of-intramuscular-

injections>

4. Ganfyd 2009, Intramuscular route, viewed 4 May 2018, <http://www.ganfyd.org/index.php?

title=Intramuscular_route>

5. Pain Community Centre 2017, Route of Administration, viewed 4 May 2018,

<http://www.paincommunitycentre.org/article/route-administration-0>

6. ResearchGate 2010, Intravenous and Subcutaneous injections: Advantages and Disadvantages, viewed 4

May 2018, <https://www.researchgate.net/figure/Intravenous-and-subcutaneous-injections-

Advantages-and-disadvantages_tbl1_45441948>

7. RxList 2018, HALDOL, viewed 4 May 2018, <https://www.rxlist.com/haldol-drug.htm#description>

8. FDA 2016, MEDICATION GUIDE, viewed 4 May 2018,

https://www.fda.gov/downloads/Drugs/DrugSafety/UCM342207.pdf

9. NPS MedicineWise 2015, Aripiprazole modified release (Abilify Maintena) for schizophrenia, viewed 4

May 2018, <https://www.nps.org.au/radar/articles/aripiprazole-modified-release-abilify-maintena-for-

schizophrenia>

10. WedMD 2017, Epinephrine Auto-Injector, viewed 8 May 2018,

<https://www.webmd.com/drugs/2/drug-76758/epinephrine-injection/details>

11. MedlinePlus 2018, Epinephrine Injection, viewed 8 May 2018,

https://medlineplus.gov/druginfo/meds/a603002.html