Niacin, or nicotinic acid, is a member of the water-soluble vitamin B family. For the most part, niacin functions as part of two important coenzymes.

Nitrous Oxide

Nitrous oxide was first identified by Joseph Priestley in 1772. Years later in the late 1790s, British chemist Humphry Davy (1778-1829) began experimenting with the effects of inhaling nitrous oxide.


Novocain is a local anesthetic (painkiller) used by doctors and dentists. It was developed as a substitute for cocaine in 1905 by German researcher Alfred Einhorn.


In 1996 the Food and Drug Administration (FDA) approved a new synthetic fat called olestra. Olestra is a sucrose polymer that has absolutely no food value.

Open-Heart Surgery

Opening the chest to operate directly on an exposed heart is major surgery. For many years the procedure was considered impossible because performing the operation would cause the heart to stop beating.


An ophthalmoscope enables a physician to examine the interior of the eye to detect abnormalities or signs of disease on the retina and lens of the eye. It does this by directing a tiny beam of light through the pupil.

Opioid Receptor

Opium has long been a drug of interest to scientists. It is one of the most effective of all pain killers.


Opium is a drug that is derived from the poppy plant. Its pain-relieving qualities have been known since ancient times.


Orthodontics is the dental specialty which deals with the positioning and relationship among the teeth within the jaw. The orthodontic goal is to move the teeth into the best position, not only for appearance, but more importantly for proper chewing, swallowing, breathing and speech.

Oxygen Tent

Around the year 1900, French physician Charles Michel (1850-1935) first realized the importance of oxygen to aid the recovery process from respiratory diseases. Oxygen helped the patients breathe easier and made them more alert by providing pure oxygen to the lung tissues and from there, into the blood.


The rhythmic, regular beating of the heart is controlled by a natural cardiac pacemaker called the sinoatrial node. This small patch of cells sends rhythmic bioelectric impulses along specific conducting fibers to the heart muscle.

Pap Test

The Pap test is a simple and relatively painless medical procedure for the early detection of cancer in women. The two most common and fatal forms of cancer are cervical and uterine.


Pasteurization is a process that uses heat to kill microorganisms. While the French chemist Louis Pasteur (1822-1895) first applied this process to wine, pasteurization is more usually recognized as being a treatment for milk.

Patent Medicine

Patent medicines first appeared in England in the 1600s. When a medication was patented, its formula was owned by the patent holder.


Penicillin is a chemical produced in common molds which has potent antibacterial properties. Bacteria are tiny organisms that have the potential to cause a huge variety of infections in every organ system of the human body.

Prenatal Diagnostic Techniques

Prenatal diagnosis is the process of determining the condition of a fetus (name given to unborn young from the end of the eighth week of development through birth) before it is born. This type of diagnosis has become an important part of pregnancy care.

Prenatal Surgery

Prenatal surgery is an invasive procedure performed on a fetus (name given to unborn young from the end of the eighth week of development through birth). An invasive procedure is one in which the fetus is penetrated by an instrument.


Quinine is an alkaloid found in the bark of the cinchona tree. Quinine has been used to treat malaria (a recurring disease marked by severe chills and fever) since the early 1600s.

Radial Keratotomy

Radial keratotomy is a surgery performed on the covering of the eyeball (the cornea). It is used to permanently correct near-sightedness, or myopia.

Radioimmunoassay (RIA)

Radioimmunoassay (RIA) is a sensitive method for measuring very small amounts of a substance in the blood. Radioactive versions of a substance, or isotopes of the substance, are mixed with antibodies and inserted in a sample of the patient's blood.