It all depends on two factors: the depth with which the needle penetrates the body and the chemical composition of the applied substances. Basically, there are four types of injection: intradermal, subcutaneous, intravenous, and intramuscular. The difference is in the point of the body they reach. The intramuscular injection, which, as the name implies, goes directly to the muscle, is the one that most bothers us because it penetrates deeper into our arms or buttocks. Already intradermal, applied to the skin, is the least painful. But, in addition to this issue of needle reach, the injected product also makes the sting more or less uncomfortable. In some injections, such as in an application of vitamin A, the active ingredient of the drug needs to be dissolved in fat, a substance that is more complicated for the body to break down and which, therefore, causes more pain to the stung patient.
At other times, the applied compound can receive an adjuvant, a substance used to give more stability to the medicine and which prolongs not only its effect but also the discomfort of the needle. There are cases in which the person can choose between taking a medicine orally or through an injection, but this is not always the case. The advantage of the sting is that the medicine has a much faster, localized action and is not influenced by other compounds produced by the body, such as stomach acids. The current trend is to try to alleviate some of the suffering of patients with injections, for example by combining several vaccines into one. “Nowadays, a single injection in the thigh allows the application of the triple bacterial, Salk, hemophilus and hepatitis vaccines”, says pediatrician Sandra de Oliveira Campos, from the Federal University of São Paulo (Unifesp).
Health professionals are even studying changes in the composition of vaccines, thinking of reducing discomfort for people. These novelties may even make bites more palatable, but injections will still have a long life in medicine.
deep suffering The further the needle goes, the more discomfort the person feels.
surface entry
Applied with a 0.4 to 0.5 millimeter gauge needle, the intradermal injection is the most superficial of all, not going beyond the layers of the skin. It serves, for example, for allergy tests, as this type of problem appears precisely on the skin. Another use is in the application of BCG, the vaccine against tuberculosis.
under the skin
With slightly thicker gauge needles, between 0.5 and 0.7 millimeters, subcutaneous injections go beyond the skin and reach the fat layer. The insulin used by diabetics is applied here. The measles vaccine as well, as it provides better defense for the body and fewer adverse effects.
straight into the vein
Intravenous injections go into a vein, where most of the antibiotics are given. Some vitamins can also be applied here. This type of injection is not usually as painful as the intramuscular injection, but depending on the substance applied, it can be very irritating. Anyone who has ever taken glucose after a big drink knows this well.
Full stop
The intramuscular is the deepest, as the needle needs to reach the person’s muscle, usually in the shoulder or buttocks. That’s why it is the most painful of injections. The dreaded Benzetacil, used against various infections, belongs to this group. Its chemical formula, made to act for a long time, makes things even worse.
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– Which injection hurts the most?
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– What happens to the medicine in the stomach?