Injecting a shot into muscle, known as an intramuscular (IM) injection, allows medication to quickly enter the bloodstream and reach the intended site of action.
How Intramuscular Injections Work
IM injections deliver medication deep into the muscle tissue. Here's a breakdown of what happens:
- Rapid Absorption: Muscles have a rich blood supply (good vascularity). This allows the injected drug to be absorbed quickly into the bloodstream.
- Systemic Circulation: Once in the bloodstream, the medication circulates throughout the body (systemic circulation). This allows the medication to reach the specific area where it's needed to take effect.
- Bypassing First-Pass Metabolism: A key advantage of IM injections is that they bypass the first-pass metabolism in the liver. This means more of the drug remains unchanged and available to work in the body. The reference states the injected drug "quickly reaches the systemic circulation and thereafter into the specific region of action, bypassing the first-pass metabolism."
Benefits of IM Injections
- Faster Onset of Action: Compared to oral medications, IM injections generally lead to a faster onset of action due to the quicker absorption rate.
- Suitable for Certain Medications: Some medications are better absorbed through intramuscular injection than other routes (e.g., orally).
- Alternative for Patients Unable to Swallow: IM injections are a useful alternative for patients who have difficulty swallowing pills.
