theanatomyandphysiologylearningsystem4epdfdr-150930024720-lva1-app6891

Chapter 2 Chemistry, Matter, and Life 31
From The Pharmacy—cont’d
States Adopted Names (USAN) council. The brand name is a trade
(proprietary) name that is assigned by the manufacturing company.
The public is most familiar with brand names because that is what is
used in advertising. Generic names are increasingly used in health
care, so the practitioner needs to be conversant with both generic
and brand names for effective communication. Here are some examples
of generic and brand names of commonly used medications.
Generic Name
Brand Name
acetaminophen
Tylenol, Datril
aspirin
Bufferin, Ecotrin
cyclobenzaprine
Flexeril
diazepam
Valium
diltiazem
Cardizem
furosemide
Lasix
ibuprofen
Advil, Motrin
warfarin
Coumadin
Medications may be classified according to the form of preparation
as oral solids, oral liquids, topical, injectable, vaginal, rectal,
ophthalmic, or otic. A few preparations (such as nasal sprays,
inhalants, implants, and insulin pumps) do not fit any of these
groups and are classified as miscellaneous.
Mixtures, Solutions, and Suspensions
Mixtures
A mixture is a combination of two or more substances, in
varying proportions, that can be separated by ordinary physical
means. The substances retain their original properties after
they have been combined in a mixture. The components of a
mixture may be elements (such as iron and sulfur), compounds
(such as sugar and water), or elements and compounds (such
as iodine and alcohol).
Solutions
Solutions are mixtures in which the component particles
remain evenly distributed. All solutions consist of two parts:
the solute and the solvent. The solute is the substance that
is present in the smaller amount and that is being dissolved.
It may be a gas, liquid, or solid. The solvent, usually a gas or
liquid, is the component that is present in the larger amount
and that does the dissolving. In a sugar solution, the sugar
is the solute and the water is the solvent. Water is the most
common solvent and is called the universal solvent. Alcohol
and carbon tetrachloride are also commonly used solvents.
When alcohol is the solvent, the solution is called a tincture.
For example, when iodine dissolves in alcohol, the solution
is called tincture of iodine. The composition of a solution is
variable; that is, it may be weak or concentrated. In a sugar
solution, whether there is a small amount of sugar or a large
amount, it is still a solution. Although a solution is always
clear and the solute does not settle, the components may be
separated by physical means such as evaporation. For example,
when the water evaporates from a sugar and water solution,
rock sugar forms.
Suspensions
Some mixtures involving a liquid settle unless they are continually
shaken. If sand is mixed with water, shaken, and then allowed
to settle, the particles of sand will fall to the bottom. This is a type
of mixture called a suspension. A suspension is cloudy and its
particles settle. Blood cells form a suspension in the plasma.
One type of mixture that is particularly important in the
body is the colloidal suspension. The particles in a colloidal
suspension are so small that they remain suspended in the liquid
but they do not dissolve. Mayonnaise, although not of particular
importance in the body, is a colloidal suspension. In this
case, the vinegar is the suspending medium and the beaten egg
provides the colloidal particles. More relevant, perhaps, is the
fact that the fluid that fills the cells of the body, the cytoplasm,
is a colloidal suspension.
Electrolytes, Acids, Bases, and Buffers
Acids, bases, and salts belong to a large group of compounds
called electrolytes. There are numerous electrolytes in the body,
and their concentrations are an important aspect of health care.
Electrolytes
Electrolytes (ee-LEK-troh-lites) are substances that break up,
or dissociate, in solution to form charged particles, or ions.
These compounds are called electrolytes because the ions can
conduct an electrical current. When an ionic compound such
as sodium chloride, NaCl, is placed in water, the positively
charged sodium ion is attracted to the negatively charged oxygen
end of the water molecule. The negatively charged chloride
ion is attracted to the hydrogens of the water molecule. Because
the polar covalent bonds of the water are stronger than the ionic
bonds of the sodium chloride, the sodium chloride breaks apart,
or dissociates, into cations and anions in the water. Figure 2-13
illustrates the dissociation of sodium chloride in water. Refer to
Table 2-2 for some of the cations and anions in the body.
Quick Applications
The electrocardiogram and electroencephalogram are
graphic tracings of the electrical currents created by
the movement of electrolytes in the heart and brain,
respectively.
Acids
Everyone is familiar with acids of various types. Orange juice,
lemon juice, vinegar, coffee, and aspirin all contain acids. Acids
have a sour taste. An acid is defined as a proton donor. Think
about the structure of a hydrogen atom: it has one proton in the
nucleus and one electron in the electron shell. When the hydrogen
atom loses its one electron and becomes a hydrogen ion, its