Getting an injection?
Where is that needle really going and … what is in that syringe?
Hi Everyone, Crystal here for DNews.
Injection is a common medical practice and all of us have to get our shots.
Whether its the chicken pox vaccine or a boost of insulin, we’ve grown to accept that injection
is a good way to administer drugs and vaccines, but how does that actually work and what is
really being injected into your body?
It turns out that what type of injection you get and the “formulation” used depends
a lot on how quickly doctors want the syringe contents to be absorbed.
This affects how often a you would need to receive an injected treatment as well as your
blood concentration of the active ingredient.
The two main types of injections are intramuscular injections, which are injected into your muscles,
and subcutaneous injections, which are injected just under your skin.
Intramuscular injections like the flu vaccine, and some steroids and anti-psychotics are
given in large muscles like your upper arm or buttocks because they need to reach the
bloodstream and take effect quickly.
This can happen because you’ve got a lot of blood circulating in your muscles to pick
up the drug and distribute it throughout your body.
Subcutaneous injections are probably the most common, and they include most vaccines and
the “insulin shots” given to diabetics.
Absorption of drugs injected under the skin is similar to that of absorption in muscles,
but since there are less blood vessels under the skin absorption can be slower.
As a chemist, I think it’s pretty cool that the absorption rate of an injected fluid is
influenced by many formulation factors as well as injection location.
Water based solutions are usually absorbed faster than oil solutions, and doctors can
“fine tune” the absorption rate, by using mixtures of oil-in-water or water-in-oil to
deliver the drug.
The composition of an injected formulation may also depend on the solubility of the active
compound so there are many factors at play here and it is controversy over the preparation
of some vaccine formulations that has lead to the anti-vax movement.
So why injection and not a pill?
Injected treatments take effect faster, are more concentrated, and don’t run the risk
of being destroyed by your stomach acid before they can do their job.
For all the good they do, there are some risks associated with injections.
Our skin exists to keep germs out and when we puncture it we leave ourselves open to
infection and transmission of disease.
This is especially true when equipment is re-used without adequate sterilization as
is frequently the case in less developed countries or in recreational drug use.
Fifteen years ago the World Health Organization estimated that, in developing and transitional
countries, unsafe injections accounted for respectively 5%, 32% and 40% of new infections
with HIV, hepatitis B virus (HBV) and hepatitis C virus (HCV).
Due to worldwide safe injection campaigns these conditions are improving, but not fast
enough.
So now that you know a little more about how they work, are you still afraid of getting
shots?
Subscribe to DNews and let us know in the comments down below.
And for a nerdy good time, come find me on Twitter @PolycrystalhD