Medicine is the applied science or practice of the diagnosis, treatment, and prevention of disease.  It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness in human beings. Contemporary medicine applies health science, biomedical research, and medical technology to diagnose and treat injury and disease, typically through medication or surgery, but also through therapies as diverse as psychotherapy, external splints & traction, prostheses, biologics, ionizing radiation and others.
Medicine has progressed over the years from ancient times to modern day and a variety of specialties have evolved due to the requirement of focus on specific sections of population (gender and age based medicine) or different parts (organs) of the body and the varied effects of their dysfunction on human health. What has kept man going has been the challenges that nature throws at him and his ability to respond to these challenges through his ingenuity (observation, inference and trial and error) culminating into the art and science that is medicine.
The challenges faced by medicine today are due to the spiraling cost of medical care (cost of imaging technology, drugs, procedures, insurance) and growing cost of medical and pharmaceutical research which prevents the poor and geriatric sections of society from accessing the health care services that are essential for them. Today there is an increase in malpractice litigation against doctors and institutions due to the increasing distrust amongst patients about doctors arising primarily from the deterioration in the doctor patient relationship.
This is in part due to the easy access to information for the patient from the internet (which he may or may not understand) and lack of time and patience on part of the doctor to address the most important aspect of the disease i. e. the anxiety that exists in the patients mind about his/her health. In the past, all medicines came from plants or animals. Although some important medicines still come from plants or animals (e. g. morphine), most medicines used today in the developed world are manufactured through chemical processes.
All new medicines must undergo thorough testing before being approved for use. Before a new medicine can be tried in humans it must undergo extensive testing in the laboratory, to assess its safety and biological activity. This ‘pre-clinical’ development stage may last as long as 3 or 4 years. Then clinical trials in human volunteers, determine if a medicine is safe and effective, at what doses it works best and what side effects it causes. A typical clinical trial development programme Stage | Number and type of patients | Typical duration | Purpose | | | | | Phase I | 20–100 healthy volunteers| up to 1 year| To ensure the medicine is safe and find the most suitable dose| | | | |
Phase II | Up to several hundred patients| 1–2 years| To assess effectiveness and look for side effects| | | | | Phase III | Several hundred to several thousand patients| 2–4 years| To confirm effectiveness and monitor any side effects from long-term use| Only one or two of thousands of new chemical compounds evaluated ever gets as far as being approved for use on prescription by doctors. It costs in the region of US$800 million to develop a new medicine and can take 12 years to make a new medicine available for doctors to prescribe.
In 2002, AstraZeneca invested over US$3 billion on research and development to improve current treatments and develop new medicines for a wide range of illnesses. Each new medicine entering development is given a chemical name (e. g. lisinopril, used to treat high blood pressure ). Occasionally, this chemical name is called something different in different countries (eg. paracetamol and acetaminophen are the same). However, once a medicine has been licensed for use in patients by the medicines agency of a country, the manufacturer can sell the medicine under a brand or trade name (eg Zestril).
Patenting of a new medicine guarantees the manufacturer a 20-year period of protection, during which no other companies can legally make or sell the medicine. However, once this period has expired, other pharmaceutical companies can make the medicine. These ‘copycat’ medicines are called ‘generic’ medicines. ‘Medicine’ as a specialty Internal medicine is the medical specialty concerned with the diagnosis, management and nonsurgical treatment of unusual or serious diseases, either of one particular organ system or of the body as a whole.
According to some sources, an emphasis on internal structures is implied.  In North America, specialists in internal medicine are commonly called “internists”. Elsewhere, especially in Commonwealth nations, such specialists are often called physicians.  These terms, internist or physician (in the narrow sense, common outside North America), generally exclude practitioners of gynecology and obstetrics, pathology, psychiatry, and especially surgery and its subspecialities.
Because their patients are often seriously ill or require complex investigations, internists do much of their work in hospitals. Formerly, many internists were not subspecialized; such general physicians would see any complex nonsurgical problem; this style of practice has become much less common. In modern urban practice, most internists are subspecialists: that is, they generally limit their medical practice to problems of one organ system or to one particular area of medical knowledge. For example, gastroenterologists and nephrologists specialize respectively in diseases of the gut and the kidneys.
 In the Commonwealth of Nations and some other countries, specialist pediatricians and geriatricians are also described as specialist physicians (or internists) who have subspecialized by age of patient rather than by organ system. Elsewhere, especially in North America, general pediatrics is often a form of Primary care. There are many subspecialities (or subdisciplines) of internal medicine: * Cardiology * Critical care medicine * Endocrinology * Gastroenterology * Geriatrics * Haematology * Hepatology * Infectious diseases * Nephrology * Oncology
* Pediatrics * Pulmonology/Pneumology/Respirology * Rheumatology * Sleep medicine. Training in internal medicine (as opposed to surgical training), varies considerably across the world: see the articles on Medical education and Physician for more details. In North America, it requires at least three years of residency training after medical school, which can then be followed by a one to three year fellowship in the subspecialties listed above. In general, resident work hours in medicine are less than those in surgery, averaging about 60 hours per week in the USA.
This difference does not apply in the UK where all doctors are now required by law to work less than 48 hours per week on average. Legal controls In most countries, it is a legal requirement for a medical doctor to be licensed or registered. In general, this entails a medical degree from a university and accreditation by a medical board or an equivalent national organization, which may ask the applicant to pass exams. This restricts the considerable legal authority of the medical profession to physicians that are trained and qualified by national standards.
It is also intended as an assurance to patients and as a safeguard against charlatans that practice inadequate medicine for personal gain. While the laws generally require medical doctors to be trained in “evidence based”, Western, or Hippocratic Medicine, they are not intended to discourage different paradigms of health Criticism of modern medicine Modern medicine is criticized for systemic bias and malpractice. According to Paul Farmer, the main problem for modern medicine is lack of access in poor regions.
There is an “outcome gap” between the rich and poor that is most noticeable with expensive-to-treat diseases like AIDS and tuberculosis. The majority of medical resources and therapies are concentrated in the rich, low-incidence regions such as the West. On the other hand, countries in the developing world have high rates of HIV but lack the resources to treat them.  Drugs A drug is a substance which may have medicinal, intoxicating, performance enhancing or other effects when taken or put into a human body or the body of another animal and is not considered a food or exclusively a food.
What is considered a drug rather than a food varies between cultures, and distinctions between drugs and foods and between kinds of drug are enshrined in laws which vary between jurisdictions and aim to restrict or prevent drug use. Even within a jurisdiction, however, the status of a substance may be uncertain or contested with respect to both whether it is a drug and how it should be classified if at all. There is no single, precise definition, as there are different meanings in drug control law, government regulations, medicine, and colloquial usage.
 In pharmacology, a drug is “a chemical substance used in the treatment, cure, prevention, or diagnosis of disease or used to otherwise enhance physical or mental well-being. “ Drugs may be prescribed for a limited duration, or on a regular basis for chronic disorders.  (Coffee is the most widely used psychoactive drug beverage in the world. In 1999, the average consumption of coffee was 3. 5 cups per day per U. S. citizen) The molecules of drugs are complex, and most of them consist of many hydrogen and carbon atoms, a few oxygen atoms, and one or a few nitrogen atoms.
Drugs may also have no nitrogen atoms in it and many may have chlorine atoms in it, such as chloral hydrate. Recreational drugs are chemical substances that affect the central nervous system, such as opioids or hallucinogens.  They may be used for perceived beneficial effects on perception, consciousness, personality, and behavior.  Some drugs can cause addiction and/or habituation.  Drugs are usually distinguished from endogenous biochemicals by being introduced from outside the organism.
 For example, insulin is a hormone that is synthesized in the body; it is called a hormone when it is synthesized by the pancreas inside the body, but if it is introduced into the body from outside, it is called a drug.  Many natural substances, such as beers, wines, and psychoactive mushrooms, blur the line between food and recreational drugs, as when ingested they affect the functioning of both mind and body and some substances normally considered drugs such as DMT (Dimethyltryptamine) are actually produced by the human body in trace amounts.
Spiritual and religious use The spiritual and religious use of drugs has been occurring since the dawn of our species. Drugs that are considered to have spiritual or religious use are called entheogens. Some religions are based completely on the use of certain drugs. Entheogens are mostly hallucinogens, being either psychedelics or deliriants, but some are also stimulants and sedatives. The cigarette is the common pharmaceutical form of tobacco – one of the world’s best selling drugs.