Pharmacology
From Wikipharm
Pharmacology (in Greek: pharmacon (φάρμακον) meaning drug, and logos (λόγος) meaning science) is the study of how substances interact with living organisms to produce a change in function.<ref name=nagle>Template:Cite book</ref> If substances have medicinal properties, they are considered pharmaceuticals. The field encompasses drug composition and properties, interactions, toxicology, therapy, and medical applications and antipathogenic capabilities.
Development of medication is a vital concern to medicine, but also has strong economical and political implications. To protect the consumer and prevent abuse, many governments regulate the manufacture, sale, and administration of medication. In the United States, the main body that regulates pharmaceuticals is the Food and Drug Administration and they enforce standards set by the United States Pharmacopoeia.
Pharmacology as a chemical science is practiced by pharmacologists. Subdisciplines include clinical pharmacology (the medical field of medication effects on humans), neuro- and psychopharmacology (effects of medication on behavior and nervous system functioning), toxicology and theoretical pharmacology.
Pharmacology is not identical with pharmacy, though in common usage the two are at times confused.
[edit] Drug legislation and safety
In the United States, the Food and Drug Administration (FDA) is responsible for creating guidelines for the approval and use of drugs. The FDA requires that all approved drugs fulfill two requirements:
- The drug must be found to be effective against the disease for which it is seeking approval.
- The drug must meet safety criteria by being subject to extensive animal and controlled human testing.
Gaining FDA approval usually takes several years to attain. Testing done on animals must be extensive and must include several species to help in the evaluation of both the effectiveness and toxicity of the drug. The dosage of any drug approved for use is intended to fall within a range in which the drug produces a theraputic effect or desired outcome.<ref name=nagle />
The safety and effectiveness of prescription drugs in the U.S. is regulated by the federal Prescription Drug Marketing Act of 1987.
[edit] Scientific background
The study of chemicals requires intimate knowledge of the biological system affected. With the knowledge of cell biology and biochemistry increasing, the field of pharmacology has also changed substantially. It has become possible, through molecular analysis of receptors, to design chemicals that act on specific cellular signalling or metabolic pathways by affecting sites directly on cell-surface receptors (which modulate and mediate cellular signalling pathways controlling cellular function).
A chemical has, from the pharmacological point-of-view, various properties. Pharmacokinetics describes the effect of the body on the chemical (e.g. half-life and volume of distribution), and pharmacodynamics describes the chemical's effect on the body (desired or toxic).
When describing the pharmacokinetic properties of a chemical, pharmacologists are often interested in ADME:
- Absorption - How is the medication absorbed (through the skin, the intestine, the oral mucosa)?
- Distribution - How does it spread through the organism?
- Metabolism - Is the medication converted chemically inside the body, and into which substances. Are these active? Could they be toxic?
- Excretion - How is the medication eliminated (through the bile, urine, breath, skin)?
Medication is said to have a narrow or wide therapeutic index or therapeutic window. This describes the ratio of desired effect to toxic effect. A compound with a narrow therapeutic index (close to one) exerts its desired effect at a dose close to its toxic dose. A compound with a wide therapeutic index (greater than five) exerts its desired effect at a dose substantially below its toxic dose. Those with a narrow margin are more difficult to dose and administer, and may require therapeutic drug monitoring (examples are warfarin, some antiepileptics, aminoglycoside antibiotics). Most anti-cancer drugs have a narrow therapeutic margin: toxic side-effects are almost always encountered at doses used to kill tumours.
[edit] Drugs used as medicines
A medication is a licensed drug (chemical) taken to cure or reduce symptoms of an illness or medical condition. Medications are generally divided into two groups -- over-the-counter (OTC) medications, which are available without special restrictions, and Prescription only medicines (POM), which must be prescribed by a physician. Most OTC medication is generally considered to be safe enough that most persons will not hurt themselves accidentally by taking it as instructed. Many countries, such as the UK have a third category of pharmacy medicines which can only be sold in registered pharmacies, by or under the supervision of a pharmacist. However, the precise distinction between OTC and prescription depends on the legal jurisdiction. Medications are typically produced by pharmaceutical companies and are often patented. Those that are not patented are called generic drugs.
