Drug in the context of Mydriasis

Medication (also called medicament, medicine, pharmaceutical drug, medicinal product, medicinal drug or simply drug) is a drug used to diagnose, cure, treat, or prevent disease. Drug therapy (pharmacotherapy) is an important part of the medical field and relies on the science of pharmacology for continual advancement and on pharmacy for appropriate management.

Drugs are classified in many ways. One of the key divisions is by level of control, which distinguishes prescription drugs (those that a pharmacist dispenses only on the medical prescription) from over-the-counter drugs (those that consumers can order for themselves). Medicines may be classified by mode of action, route of administration, biological system affected, or therapeutic effects. The World Health Organization keeps a list of essential medicines.

A biopharmaceutical, also known as a biological medical product, or biologic, is any pharmaceutical drug product manufactured in, extracted from, or semisynthesized from biological sources. Different from totally synthesized pharmaceuticals, they include vaccines, whole blood, blood components, allergenics, somatic cells, gene therapies, tissues, recombinant therapeutic protein, and living medicines used in cell therapy. Biopharmaceuticals can be composed of sugars, proteins, nucleic acids, or complex combinations of these substances, or may be living cells or tissues. They (or their precursors or components) are isolated from living sources—human, animal, plant, fungal, or microbial. They can be used in both human and animal medicine.

Terminology surrounding biopharmaceuticals varies between groups and entities, with different terms referring to different subsets of therapeutics within the general biopharmaceutical category. The term biologics is often used more restrictively to mean biopharmaceuticals that are produced using recombinant DNA technology. Some regulatory agencies use the terms biological medicinal products or therapeutic biological product to refer specifically to engineered macromolecular products like protein- and nucleic acid-based drugs, distinguishing them from products like blood, blood components, or vaccines, which are usually extracted directly from a biological source. Biopharmaceutics is pharmaceutics that works with biopharmaceuticals. Biopharmacology is the branch of pharmacology that studies biopharmaceuticals. Specialty drugs, a recent classification of pharmaceuticals, are high-cost drugs that are often biologics. The European Medicines Agency uses the term advanced therapy medicinal products (ATMPs) for medicines for human use that are "based on genes, cells, or tissue engineering", including gene therapy medicines, somatic-cell therapy medicines, tissue-engineered medicines, and combinations thereof. Within EMA contexts, the term advanced therapies refers specifically to ATMPs, although that term is rather nonspecific outside those contexts.

A medical abortion, also known as medication abortion or non-surgical abortion, occurs when drugs (medication) are used to bring about an abortion. Medical abortions are an alternative to surgical (also called procedural or instrumentation) abortions such as vacuum aspiration or dilation and curettage. Medical abortions are more common than surgical abortions in most places around the world.

Medical abortions are most commonly performed by administering a two-drug combination: mifepristone followed by misoprostol. This two-drug combination is more effective than other drug combinations. When mifepristone is not available, misoprostol alone may be used in some situations.

Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms. Study of structure determines their structural formula. Study of properties includes physical and chemical properties, and evaluation of chemical reactivity to understand their behavior. The study of organic reactions includes the chemical synthesis of natural products, drugs, and polymers, and study of individual organic molecules in the laboratory and via theoretical (in silico) study.

The range of chemicals studied in organic chemistry includes hydrocarbons (compounds containing only carbon and hydrogen) as well as compounds based on carbon, but also containing other elements, especially oxygen, nitrogen, sulfur, phosphorus (included in many biochemicals) and the halogens. Organometallic chemistry is the study of compounds containing carbon–metal bonds.

Pharmacy is the science and practice of discovering, producing, preparing, dispensing, reviewing and monitoring medications, aiming to ensure the safe, effective, and affordable use of medicines. It is a miscellaneous science as it links health sciences with pharmaceutical sciences and natural sciences. The professional practice is becoming more clinically oriented as most of the drugs are now manufactured by pharmaceutical industries. Based on the setting, pharmacy practice is either classified as community or institutional pharmacy. Providing direct patient care in the community of institutional pharmacies is considered clinical pharmacy.

The scope of pharmacy practice includes more traditional roles such as compounding and dispensing of medications. It also includes more modern services related to health care including clinical services, reviewing medications for safety and efficacy, and providing drug information with patient counselling. Pharmacists, therefore, are experts on drug therapy and are the primary health professionals who optimize the use of medication for the benefit of the patients. In some jurisdictions, such as Canada and Australia, Pharmacists may be able to prescribe or adapt/manage prescriptions, as well as give injections and immunizations.

Drug injection is a method of introducing a drug into the bloodstream via a hollow hypodermic needle, which is pierced through the skin into the body (usually intravenously, but also at an intramuscular or subcutaneous, location). Intravenous therapy, a form of drug injection, is universally practiced in modernized medical care. As of 2004, there were 13.2 million people worldwide who self-administered injection drugs outside of medical supervision, of which 22% are from developed countries.

A wide variety of drugs are injected, often opioids: these may include legally prescribed medicines and medication such as morphine, as well as stronger compounds often favored in recreational drug use, which are often illegal. Ketamine administered intravenously in clinical settings has become more common. Although there are various methods of taking drugs, injection is favoured by some people as the full effects of the drug are experienced very quickly, typically in five to ten seconds. It also bypasses first-pass metabolism in the liver, resulting in higher bioavailability and efficiency for many drugs (such as morphine or diacetylmorphine/heroin; roughly two-thirds of which is destroyed in the liver when consumed orally) than oral ingestion would. The effect is that the person gets a stronger (yet shorter-acting) effect from the same amount of the drug. Drug injection is therefore often related to substance dependence.

Fluorocarbons are chemical compounds with carbon-fluorine bonds. Compounds that contain many C-F bonds often have distinctive properties, e.g., enhanced stability, volatility, and hydrophobicity. Several fluorocarbons and their derivatives are commercial polymers, refrigerants, drugs, and anesthetics.

Pharmacodynamics (PD) is the study of the biochemical and physiologic effects of drugs (especially pharmaceutical drugs). The effects can include those manifested within animals (including humans), microorganisms, or combinations of organisms (for example, infection).

Pharmacodynamics and pharmacokinetics are the main branches of pharmacology, being itself a topic of biology interested in the study of the interactions of both endogenous and exogenous chemical substances with living organisms.

Drug design, often referred to as rational drug design or simply rational design, is the inventive process of finding new medications based on the knowledge of a biological target. The drug is most commonly an organic small molecule that activates or inhibits the function of a biomolecule such as a protein, which in turn results in a therapeutic benefit to the patient. In the most basic sense, drug design involves the design of molecules that are complementary in shape and charge to the biomolecular target with which they interact and therefore will bind to it. Drug design frequently but not necessarily relies on computer modeling techniques. This type of modeling is sometimes referred to as computer-aided drug design. Finally, drug design that relies on the knowledge of the three-dimensional structure of the biomolecular target is known as structure-based drug design. In addition to small molecules, biopharmaceuticals including peptides and especially therapeutic antibodies are an increasingly important class of drugs and computational methods for improving the affinity, selectivity, and stability of these protein-based therapeutics have also been developed.

A controlled substance is generally a drug or chemical whose manufacture, possession, and use is regulated by a government, such as illicitly-obtained drugs or prescription medications that are designated by law. Some treaties, notably the Single Convention on Narcotic Drugs, the Convention on Psychotropic Substances, and the United Nations Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances, provide internationally agreed-upon "schedules" of controlled substances, which have been incorporated into national laws; however, national laws usually significantly expand on these international conventions.

Some precursor chemicals used for the illegal production of 'controlled drugs' are also controlled substances in many countries, even though they may lack the pharmacological effects of the drugs themselves. Substances are classified according to schedules and consist primarily of potentially psychoactive substances and anabolic steroids. The controlled substances do not include many prescription items such as antibiotics.

Substance misuse, also known as drug misuse or, in older vernacular, substance abuse, is the use of a drug in amounts or by methods that are harmful to the individual or others. It is a form of substance-related disorder, differing definitions of drug misuse are used in public health, medical, and criminal justice contexts. In some cases, criminal or anti-social behavior occurs when some persons are under the influence of a drug, and may result in long-term personality changes in individuals. In addition to possible physical, social, and psychological harm, the use of some drugs may also lead to criminal penalties, although these vary widely depending on the local jurisdiction.

Drugs most often associated with this term include alcohol, amphetamines, barbiturates, benzodiazepines, cannabis, cocaine, hallucinogens, methaqualone, and opioids. The exact cause of substance abuse is sometimes clear, but there are two predominant theories: either a genetic predisposition or most times a habit learned or passed down from others, which, if addiction develops, manifests itself as a possible chronic debilitating disease. It is not easy to determine why a person misuses drugs, as there are multiple environmental factors to consider. These factors include not only inherited biological influences (genes), but there are also mental health stressors such as overall quality of life, physical or mental abuse, luck and circumstance in life and early exposure to drugs that all play a huge factor in how people will respond to drug use.

A drug cartel is a criminal organization composed of independent drug lords who collude with each other in order to improve their profits and dominate the illegal drug trade. Drug cartels form with the purpose of controlling the supply of the illegal drug trade and maintaining prices at a high level. The formations of drug cartels are common in Latin American countries. Rivalries between multiple drug cartels cause them to wage turf wars against each other. Drug cartels often transport both drugs and narcotics, and most often the term "Narcotics cartel" is not used to describe an organization that transports the latter legally defined set of illegal substances, such as marijuana.

Drugs considered addictive or dangerous in the United Kingdom are called "controlled substances" and regulated by law. Until 1964 the medical treatment of dependent drug users was separated from the punishment of unregulated use and supply. Under this policy drug use remained low; there was relatively little recreational use and few dependent users, who were prescribed drugs by their doctors as part of their treatment. From 1964 drug use was decreasingly criminalised, with the framework still in place as of 2014 largely determined by the Misuse of Drugs Act.

Chemical castration is castration via anaphrodisiac drugs, whether to reduce libido and sexual activity, to treat cancer, or otherwise. Unlike surgical castration, where the gonads are removed through an incision in the body, chemical castration does not remove organs and is not a form of sterilization.

Chemical castration is generally reversible when treatment is discontinued, although permanent effects in body chemistry can sometimes be seen, as in the case of bone density loss increasing with length of use of depot medroxyprogesterone acetate (DMPA). In men, chemical castration reduces sex drive and the capacity for sexual arousal, side effects of some drugs may include depression, suicidal ideation, hot flashes, anemia, infertility, increase in body fat and higher risks of cardiovascular diseases and osteoporosis. In women, chemical castration acts by decreasing testosterone levels in order to lower their sex drive, side effects include the deflation of breast glands, expansion of the size of the nipple and shrinking of bone mass.

Behavioral neuroscience, also known as biological psychology, biopsychology, or psychobiology, is part of the broad, interdisciplinary field of neuroscience, with its primary focus being on the biological and neural substrates underlying human experiences and behaviors, as in our psychology. Derived from an earlier field known as physiological psychology, behavioral neuroscience applies the principles of biology to study the physiological, genetic, and developmental mechanisms of behavior in humans and other animals.

Behavioral neuroscientists examine the biological bases of behavior through research that involves neuroanatomical substrates, environmental and genetic factors, effects of lesions and electrical stimulation, developmental processes, recording electrical activity, neurotransmitters, hormonal influences, chemical components, and the effects of drugs. Important topics of consideration for neuroscientific research in behavior include learning and memory, sensory processes, motivation and emotion, as well as genetic and molecular substrates concerning the biological bases of behavior. Subdivisions of behavioral neuroscience include the field of cognitive neuroscience, which emphasizes the biological processes underlying human cognition. Behavioral and cognitive neuroscience are both concerned with the neuronal and biological bases of psychology, with a particular emphasis on either cognition or behavior depending on the field.