Pharmacodynamics is the science that studies and describes the effects of medications and drugs on the body, as well as their mechanisms of action and the relationship between the dose and the effects caused.
When a drug is ingested, absorbed, or injected, it enters the bloodstream and, as it travels through the body, produces effects in various target sites.
The drug's interaction at the affected site produces the desired reaction, but its interaction with other cells, organs and tissues can cause undesirable effects or side effects.
Some examples of side effects are increased chances of cell mutation, drug-induced illnesses, and drug hypersensitivity.
Classification of drugs
With respect to action mechanisms, the drugs can be divided into two groups:
Structurally unspecific
These drugs, to cause effects in the body depend only on their physicochemical properties., that is, they do not bind to a cellular component to take effect.
One of the examples of structurally unspecific drug are fruit salts, which are antacids that reduce the acidity of gastric juice just because of their physicochemical properties.
structurally specific
In this case, the drug interacts with a cellular component, which can be an enzyme, a signaling protein, or an ion channel.
This interaction can be exemplified with a key and a lock, where the key is the drug and the lock is the target in the cell. The drug reaction happens when the two bond.
The study of the relationship between a drug and the body considers factors such as the body's response to the drug; the effects caused; the relationship between substance concentration and effect intensity and mechanism and site of action.
Two other important concepts of pharmacodynamics are affinity and intrinsic activity:
- Affinity: affinity is the ability of the drug to bind to its cellular target;
- Intrinsic Activity: it is the ability of the drug to trigger an action within the cell after it has attached itself to its target.
When there is intrinsic affinity and activity, the drug is considered agonist. That is, it binds and causes a reaction in the cell.
There is also the possibility that the drug only binds to the cellular target, but does not promote any action in the body, that is, it does not have an intrinsic activity. In this case, the drug is classified as antagonist.
Even if there is no intrinsic activity, it is possible for the drug to produce pharmacological effects.
In the case of antihistamines used as antiallergics, for example, by binding to the cell target, they block the allergens from their receptors and thus block the allergy.
know more about side effect
Pharmacodynamics and pharmacokinetics
Pharmacodynamics is the area that studies the physiological effects of drugs on organisms, their relationship with cell targets and the production of undesirable or side effects.
Pharmacokinetics, in turn, is the path that the drug takes in the body. This path consists of the following steps: absorption, distribution, biotransformation and excretion.
See more about pharmacokinetics.
