What is a medicine?




A medicine is a substance that is used to cure a disease or alleviate its symptoms. A medicine can also be used to prevent diseases (such as anti-malarial drugs**) or to make a medical diagnosis.


The nomenclature used to describe a drug can be defined as:

Scientific name

The scientific name of a medicine is the one used by physicians and pharmacists.

Registered name

The registered name is the name given to it by the laboratory that prepares it.


A medicine is made up of:

Active ingredient

The substance that has a therapeutic effect. The same medicine may contain more than one active ingredient, each meant to cure or alleviate different symptoms.


A substance that is part of the medicine but has no therapeutic effect. It is used to get the desired pharmaceutical form (capsules, tablets, syrups, etc.) and it facilitates the medicine’s preparation and administration. The substances used to make the excipients depend on the kind of medicine. For example, a sugar-based excipient would not be used in a medicine prescribed for diabetes, and gluten would not be used in one prescribed for sufferers of celiac disease.

What is a generic medicine?

A generic drug is a non-propriety name drug whose patent protection has expired. It is just as safe and effective as a brand drug, it has the same composition (both qualitatively and quantitatively) and, in Spain, it can be distinguished because it has the name of the active substance on the label (e.g.: ibuprofen) followed by the name of the pharmaceutical company and the initials GPE (Generic Pharmaceutical Equivalent).


Of public domain

Safe and effective

Main risks of medication


Side effects, adverse reactions and intoxication.

Dependence or addiction

Especially in medications prescribed to treat psychological disorders.


Taking different medicines at the same time can be dangerous.


Because they are not indicated for that particular disease, because the dose is wrong or because the medicine is administered for an inadequate period of time.

Erroneous diagnosis

By hiding symptoms, some medicines can mask or alter a disease, making it difficult to diagnose or leading to an erroneous diagnosis.

Classification of medicines

By its purpose


These medicines treat diseases caused by the absence or insufficiency of some substance, such as vitamin D for rickets and insulin for diabetes.

Stimulation or reduction of cellular activity

One example is vaccinations, which stimulate the production of antibodies by the cells in the immune system.


These medicines try to destroy or impede the action of a microorganism (bacteria, virus, fungus) that causes an infection.

By the way it is administered


One of the most common ways. Some products (like certain antibiotics) cannot be ingested because the gastric juices would destroy them.


It is injected with a thicker, longer needle because it has to reach the muscle.


Also called topical medications, they are applied on the skin in the form of a gel or ointment.


The medicine is inserted into the anus in the form of a suppository. This means is not used very frequently because the amount of medicine that goes to the blood fluctuates greatly and its effect is variable.


The medicine penetrates the body to the lungs in the form of an aerosol. This is particularly used in the case of asthma.


The classic medicines administered through the nose are nasal decongestants, although they can have a rebound effect and increase congestion once the medicine loses effect.


This is injected directly into a vein. The medicine acts the most quickly with intravenous administration.


The injection reaches the subcutaneous tissue located between the skin and the muscles. These injections are usually administered in the arms, but they can also be in the thighs, buttocks or stomach. Insulin and some vaccinations tend to be administered in this way.


These medicines are applied directly in the eyes in the form of drops or ointments.


These medicines are administered under the tongue, which is an area with many blood vessels, so medicines that dissolve there act more quickly. Some medicines for hypertension or tranquilizers are administered sublingually.


The medicine reaches the body through the outer ear. This is often used in outer ear infections.


This is particularly used to treat infectious diseases of the vagina, such as candidiasis.

By its therapeutic action


They are used to… Eliminate or lower pain. Morphine derivatives** have narcotic effects and are used when the pain is very intense or visceral. Analgesics that do not come from morphine, such as paracetamol, also lower inflammation and fever.
Be careful… Acetylsalicylic acid** is a very well known, effective analgesic, but it affects the stomach and is not recommended for people with gastric problems.

For the digestive tract

They are used for… Acidity and ulcers, vomiting, diarrhea, constipation, flatulence, etc.
Be careful… … Improper use may aggravate the problem it is supposed to treat. Overusing a laxative, for example, can cause constipation. If the diarrhea is caused by an infection, an anti-diarrheal will make the microbes that are causing the infection remain in the intestine for longer.

For the respiratory tract

They are used for… Congestion, cough, mucus, asthma, chronic bronchitis, etc.
Be careful… In diseases that cause a great deal of mucus in the lungs, such as chronic bronchitis, cough medicine can prevent the sufferer from expelling the mucus.


They are used for… Skin infections, itchiness, psoriasis, acne, warts, callouses, etc.
Be careful… Medicines applied on the skin often pass into the bloodstream and from there spread to the entire body, so they can have side effects just like medicines that are ingested or administered intramuscularly. This is particularly true when the skin has wounds. Furthermore, the side effects of many medicines appear on the skin: eruptions, redness, rashes, allergies, sun sensitivity, etc. Anti-acne medicines administered orally can cause severe fetal malformations.

For endocrine diseases

They are used to… Treat diseases related to the glands that produce hormones, such as diabetes and hypothyroidism.
Be careful… Improper use of corticoids, medicines which are similar to the hormones produced by the suprarenal glands, can lead to osteoporosis, high blood pressure and digestive hemorrhaging, among others.


They are used to… Anemia, clotting disorders, etc.
Be careful… In excess, they can cause hemorrhaging y hematomas.


They are used to… Combat infections caused by bacteria.
Be careful… Antibiotics can do nothing against viruses (such as the flu), and if they are taken needlessly they can make bacteria become resistant to them. Plus, excessive and unjustified consumption of antibiotics can end up damaging the “friendly” microbes in our body, which are housed in areas like the intestinal flora and are beneficial to our health.


They are used for… Angina, heart failure, arrhythmia, hypertension, lowering cholesterol and triglycerides, etc.
Be careful… Generally speaking, medicines are fairly toxic, and some can lead to heart disorders and even aggravate the initial situation.


They are used to… Combat the action of histamine, a natural substance in the body which triggers the effects of allergies. Discover more about allergies here.
Be careful… Some antihistamines also act on the central nervous system and cause sleepiness, so they should not be combined with driving, drinking alcohol and doing certain jobs.

For the central nervous system

They are used to… Put a patient totally to sleep (general anesthesia) or put only part of the body to sleep (local).
Be careful… They can cause heart problems (this is why a study of the condition of the patient’s heart is always needed before administering anesthesia) and psychological problems when the patient wakes up.

For psychological disorders
They are used for… Psychological disorders (anxiety, depression, schizophrenia, neurosis, etc.) and sleep disorders.
Be careful… These are particularly dangerous medicines, and abusing them can cause serious problems and even death. They act on the central nervous system and are therefore capable of altering the behavior of the person taking them. Chronic use of some of these medicines can create dependency. It is dangerous to drink alcohol when using them.


They are used to… Treat cancer.
Be careful… They often have serious side effects which require the treatment to be stopped. Sometimes they can also affect the healthy cells in the body, although the treatments are increasingly advanced and attack only the cancerous cells.

Medicine during pregnancy

A medicine’s ability to harm the fetus depends on the amount taken and its toxicity, but the stage in the pregnancy and the amount of time it is taken also matter.

Up 17 days after fecundation

It is harder for the medicine to affect the fetus.

From days 17 to 60.

The embryo is more vulnerable, since its organs are in the process of developing. Medicine can cause miscarriage or a congenital anomaly.

After the first trimester

Medicine may alter the growth and function of the organs and tissues, as well as the placenta, by lowering the exchange of oxygen and nutrients between the fetus and the mother. They can also cause contractions of the uterine muscles and lower the amount of blood that the fetus receives.


  1. During pregnancy, it is more important than ever not to take a medicine if it is not strictly necessary.
  2. If you do have to take medicine, always check with your physician and/or gynecologist first.
  3. There are certain chronic diseases, such as epilepsy, asthma or diabetes, whose treatment cannot be interrupted, since the risk of not taking medicine is greater than the risk of taking it.
  4. There are medicines and vitamin complexes that are especially designed for pregnant women, such as folic acid, antacids, and those that relieve constipation, vomiting and hemorrhoids.