THE CONSTRUCTION OF FORMULAE FOR SWEET TABLETS.
Choice of Flavor.
THERE are quite a number of medicines sufficiently free from taste
and odor to be made perfectly pleasant by the mere admixture of sugar
and of flavoring. These can, of course, be prepared with any flavor
desired. In the formulary, rose has been chosen as the flavor under
these circumstances, but any other flavor may be used instead.
Substances that have a slightly acrid taste are generally best
disguised by peppermint. For sour taste, lemon is best. Wintergreen was
chosen as the flavor for salicylates.
Substances that have a slightly bitter taste are best disguised by
"vanilla cacao sugar." For drugs that, in addition to a slightly bitter
taste, have an odor that needs disguising, "cinnamon cacao sugar" is to
be preferred.
The Subduing of Tastes.
There are quite a number of drugs that have a tendency to leave a
rather persistent disagreeable after-taste, drugs of slight solubility,
particles of which remain on the tongue longer than the sugar
does, so that their taste lingers after the taste of the sugar has
disappeared. For such drugs saccharinization solves the problem of
candy medication. The saccharin will be most efficient, as the author
has shown by repeated experiments, if it is directly incorporated with
the drug in solution rather than in dry form. Saccharinization is,
therefore, carried out in the formulary by triturating the drug with a
saturated (3 per cent.) alcoholic solution of saccharin, and permitting
the alcohol to evaporate subsequently. The drying may be expedited by
using a hot mortar. When alcohol is not permissible, as in the case
of "Alcresta" preparations (see below), dry saccharinization must be
used instead, that is, triturating the drug with saccharin, preferably
a 1 to 10 trituration. Likewise when time does not permit moist
saccharinization, triturating the substance with a somewhat larger
amount of saccharin will answer the purpose.
A second expedient for the subduing of taste is fat covering, which
consists of triturating the drug with liquid petrolatum or other fat,
e. g., Crisco in ether, and permitting the ether to evaporate. The thin
film of fat left on the drug delays its solution to a slight degree,
yet sufficiently to reduce the taste, so that certain drugs--such
as aspirin, digitalis, diuretin--can be administered in the form of
sweet tablets in useful dose. In these cases, saccharinization and fat
covering combined give the best results.
* * * * *
Most of the alkaloids can be administered in candy form by
saccharinization with or without additional fat covering, and, in the
case of some, the addition of sodium bicarbonate is still further
useful in lessening the solubility, thereby subduing the taste. Only
in the case of the bitterest alkaloids such as strychnine and of
alkaloids that have to be given in large doses such as quinine are
different expedients necessary. For quinine, aristochin or saloquinine
solve the problem. For strychnine, Lloyd's "Alcresta" strychnine gives
good results. In 1910, John Uri Lloyd[9] of Cincinnati discovered
that the addition of fuller's earth to alkaloids almost completely
abolished their bitter taste. He found on further research that this
activity resided in the finest particles, especially those of colloidal
dimensions, which could be separated from the coarser portion of
fuller's earth by elutriation. By means of this powder, now known as
Lloyd's Reagent, it is possible to obtain the bitterest alkaloids, even
strychnine, in almost tasteless form. That this strychnine combination
is still active, can be proved by the fact that it will kill a dog
almost as readily as the uncombined strychnine. Lloyd has coined the
name "Alcresta" for these alkaloidal combinations; they are marketed
by Ely Lilly and Company. The combination of the strychnine with
fuller's earth is destroyed by alkali and by alcohol. Hence alcohol
must not be added to the powder after the Alcresta combination has been
incorporated. The addition of a little acid lessens the bitterness of
the combination by lessening solubility in the mouth. The addition of
acid is also of advantage to lessen the solubility in the saliva, and
with it the taste, of such resinous bodies as the resin of podophyllum.
Choice of Color.
To indicate tablets containing poisonous substances, a dark red color
is chosen, unless cacao disguises the taste better. It would be
advisable not to prescribe more than a small number of such tablets
to be dispensed at one time, so as to prevent the possibility of
poisoning. The choice of the other colors has been more or less
without special principle underlying it, yellow having been chosen for
lemon, and green for wintergreen, leaving pink for rose and white for
peppermint. The relation of color to flavor can, of course, be varied.