Pharmacodynamics

Pharmacodynamics is the study of how drugs affect the body. Drugs are chemicals that induce changes in the human body. Most often, drugs are prescribed by doctors and are given in carefully controlled dosages to treat a particular illness or condition. Other drugs are taken for nonmedicinal purposes. These can include legal drugs such as alcohol and caffeine, or illegal substances such as heroin and cocaine, and many other substances that produce an altered state of consciousness.

Pharmacodynamics is concerned with the factors that influence how strong the effect of a particular dosage is in a given person. Numerous factors influence the strength of a particular dosage of a drug. For example, some drugs cause users to build up resistance and require a larger dose to achieve the same result. Mixing drugs can cause them to react in a dangerous manner, drastically increasing or decreasing the strength of the dosage. Even the age of the user plays a significant role in determining the correct dosage of a drug.

Background

Drugs are chemicals that, when ingested, affect the chemistry of the brain or the way the body functions. Drugs can have a wide variety of effects on the human body. Some drugs can help the body heal, while others can disrupt its functions in several negative ways. Many people take drugs intentionally, seeking to enact specific changes on how their body is functioning. Sometimes these drugs are prescribed by a doctor.

Drugs prescribed by doctors to diagnose, treat, or cure a disease are considered pharmaceutical drugs, or more simply, medicine. Medicine can help the body treat the illness itself or the symptoms that accompany an illness. For example, antibiotics are drugs that kill bacteria, helping fight potentially harmful bacterial infections. Analgesics are medicines that reduce pain, while antipyretics help reduce fever.

Some medical drugs are designed to assist mental health instead of physical health. They change a person’s mood or thought patterns. For example, people who suffer from depression may benefit from controlled doses of antidepressants. Similar classifications of drugs include antipsychotics, sedatives, mood stabilizers, and antianxiety medications.

Other drugs used for nonmedicinal purposes and are often regulated or even illegal. Like pharmaceutical drugs, taking these drugs results in changes to the way the human body functions. However, most are taken without the input of a doctor and are used for recreational purposes, not to treat a medical illness.

Recreational drugs can induce a wide range of effects on the body. For this reason, clinicians often divide them into several categories. Stimulants, such as caffeine and cocaine, make users feel energetic, talkative, and excited. Depressants, such as alcohol and sleeping pills, make users feel relaxed and sleepy. Opium-related painkillers are usually based on the drug morphine. They create feelings of euphoria and put users in a drowsy state. Hallucinogens make users feel detached from themselves or their surroundings. They may also cause strange psychological experiences, hallucinations, and an altered sense of time.

Some drugs are more dangerous than others. For example, users of cocaine are at greater risk of bodily harm than users of caffeine. Many drugs can cause permanent harm or death if taken in an incorrect dosage. Additionally, many drugs are addictive, meaning the drug changes the chemistry of the brain so that the body becomes dependant on the chemicals in the drug. This can cause painful withdrawal symptoms if the user fails to take an expected dosage. For this reason, any patient prescribed a potentially addictive drug by a doctor must be carefully monitored for symptoms of dependency.

Overview

Pharmacodynamics is the study of the chemical, biological, and psychological effects drugs have on the human body. It includes both the changes themselves and how drugs induce those effects. Pharmacodynamics also studies how the effects of drugs can be increased, reduced, or changed. To track these effects, scientists study receptor bindings, postreceptor effects, and chemical interactions.

The human body contains numerous receptors, special proteins on the surface of cells that bind to a specific chemical or substance. Molecules from substances such as drugs and hormones that bind themselves to receptors are called ligands. In most cases, the binding of a ligand and a receptor is temporary. When a receptor is bound, it induces a particular effect in the body. For example, activating a certain receptor might increase or decrease a type of cell function.

Not all molecules can bind to some receptors. In most cases, receptors only bind to a specific subset of molecules. A greater understanding of how drugs match to particular receptors within the body gives researchers significant insight into how the body will react to the presence of a particular drug.

The effects of a drug on the body can be increased or decreased by various mechanisms. Some ligands are naturally more efficient than others. Efficient ligands easily bind to receptors and induce a greater response from cells. This results in a more intense reaction from the body.

Some effects are influenced by how long a ligand remains bound to a receptor. However, many other factors may influence the effect of a drug on the body. For example, repeated exposure to some drugs causes the body to build up a resistance to it. Over time, the same dosage of a drug will result in weakened effects.

External factors can also influence the body’s reaction to a particular drug. The presence of other drugs can increase or decrease the impact of a new drug on the body. In some cases, the interactions between two drugs can be unpredictable or dangerous for the user. A combination of drugs may cause similar chemicals to compete for the same receptors, reducing the effects of both drugs, or it may cause a dangerous increase in the drug’s effects. Additionally, the aging process alters receptor binding and postreceptor sensitivity. This causes older or very young people to respond to drugs differently than the average adult.

Bibliography

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