b. Fusion Method. The fusion method is particularly useful when solid waxes
are included in the ointment to add viscosity. In this method, first melt the substance
with the highest melting point by using a water bath, but use as little heat as necessary.
Then add the other ingredients on the basis of their decreasing melting points. When
the entire mixture is liquefied, remove it from the water bath. Then stir the mixture until
it congeals, to prevent possible separation and crystallization.
Ointments are traditionally packaged in jars and collapsible tubes. The jars are
made of glass that is either green or opaque white. Ordinary tin tubes are convenient to
the patient because they are easier to carry and do not break when they are dropped.
They are especially valuable for ointments that lose moisture or decompose on
exposure to the atmosphere.
a. Filling Ointment Jars. Ointment jars, available in many sizes ranging from
1/4 ounce to a pound and larger, may be filled by packing the ointment into them with a
small spatula. In packing, the sides and bottom all the way around should be covered
first, adding the final portions to the center and top in order to minimize air pockets.
Melted ointments containing no material likely to settle out may be poured into
containers while still warm and fluid. In either case, the ointment should be smoothed
off at the top before the lid is closed.
b. Filling Ointment Tubes. You can fill ointment tubes at the pharmacy by first
rolling the ointment into a glassine powder paper to make a cylinder just smaller than
the base of the tube. Remove the cap of the tube so that air will not be trapped when
the ointment is inserted. Insert the roll, ointment and paper combined, as far into the
tube as the roll will go and close it by carefully flattening the end of the tube. Hold the
end of the tube closed with firm pressure from the side of a spatula and carefully pull the
glassine paper out of the tube. The ointment is left in the tube. Fold the end of the tube
over twice, crease it tightly, and score it several times with the spatula edge to prevent it
from opening during use.
c. Labeling. Select a label corresponding in size to the size of the jar being
used. Metal ointment tubes should be moistened with tincture of benzoin before the
label is applied to help the label adhere. When the label has been put into place, it
should be covered with a strip of cellophane tape. The auxiliary label "For External Use
Only" is required on all ointments, pastes, and creams.
Section II. SUPPOSITORIES
Suppositories are solid bodies of various weights and shapes, adapted for
introduction into different orifices of the human body, usually the rectum or vagina.
Suppositories usually dissolve, melt, or soften at body temperature.