THE MAKING OF SWEET TABLETS.
IT IS GENERALLY supposed that tablet making is an art, requiring
special expertness and expensive machinery. Now while both of these
ideas are correct when the preparation of a large variety of tablets
and of large quantities is contemplated, they are erroneous in regard
to the making of prescription quantities of these sweet tablets, which
present a comparatively simple and relatively uniform problem in tablet
making.
Though the process of making moulded tablets was introduced by Dr.
Robert M. Fuller of New York before the Academy of Medicine on February
21, 1878, in a paper entitled: "Dose-Dispensing Simplified,"[4] the
simplification was evidently not such that druggists could notice it;
for moulded tablets have not become popular among them, perhaps mainly
because they require drying. Likewise are compressed tablets, which
were introduced even earlier by Professor Brockeden of England in 1844,
considered unsuitable for extemporaneous preparation, as granulation
of the powder by moistening is believed to be necessary; and this, of
course, also requires drying.
A step in the direction of rendering tablet making available for
extemporaneous preparation was made in 1909 by A. Schleimer[5] by
advocating the use of cacao butter in lieu of granulation of the
powder and subsequent drying. This brings tablets into the category
of extemporaneous preparations. All that is necessary is to add three
percent of cacao butter to the powder, and it is ready for immediate
compression in a tablet machine. Having found that cacao butter is
liable to become rancid on keeping of some tablets made with it, the
author experimented to find a substitute devoid of this tendency, and
found it in paraffin of low melting point.[6] For tablets that are
not to be kept for any length of time, cacao butter is preferable, as
it melts readily and is digestible. The amount of paraffin, however,
that enters into the composition of each tablet is so small that in
spite of its indigestibility, it seems that it could not meet with any
but theoretic objection. Either of these materials, in form of fine
shavings, is added to the extent of three to five per cent. with just
sufficient trituration to distribute fairly well. Excessive trituration
lessens the efficiency of the lubricating agent. If the tablet has a
tendency to stick to the punches, the material can be worked better if
a little talcum, say three per cent. is added to the powder by stirring
it in with a spatula rather than by trituration. This process renders
tablet making no more difficult or time-consuming than the making of
pills or capsules.
* * * * *
The author has succeeded in still further simplifying the process by
the preparation of what he would propose to call "fat sugar." Having
noticed that the addition of, say, 10 per cent. of powdered cacao to
sugar forms an almost ideal powder for immediate compression in the
tablet machine, the idea occurred to him to reproduce, as nearly as
possible, the physical condition of cacao by covering each particle of
powdered starch with a thin layer of fat, which can readily be done by
triturating starch with liquid petrolatum. While other fat, such as
cacao butter, "Crisco" or paraffin, might be used for this purpose, by
dissolving the fat in ether and thus distributing it over the starch,
permitting the ether subsequently to evaporate, the author has found
that liquid petrolatum, 1 part, distributed over 3 parts of starch
forms a powder which added to sugar in proportion of about twenty
per cent. renders it admirably suitable for compression in a tablet
machine. The starch might be sweetened by previously triturating it
with an alcoholic solution of saccharin and permitting the alcohol to
evaporate; though this sweetening is not essential. For starch, thus
prepared, the author proposes the name "fat starch", the formula for
which will be found in Chapter VIII. Sugars containing twenty per cent.
of "fat starch", are ready for immediate compression in the tablet
machine; and admit of admixture of a moderate amount of medicament
without losing this quality. If a large amount of medicament is to
be incorporated, then an additional amount of "fat starch" should
be allowed. Sugars containing "fat starch" the author has called
"fat sugars" for want of a better name. He is aware of the fact that
petrolatum is not a fat in the true sense of the word. Nevertheless
it is, no doubt, its "fatty" nature that does the work; other fatty
substances, such as cacao butter or "Crisco", producing the same result
as far as rendering the powder suitable for compression in the tablet
machine is concerned. Liquid petrolatum has the advantage over these of
being devoid of tendency to rancidity.
Excessive trituration interferes with the efficiency of the fat starch,
evidently by distributing the fat all over the powder, rendering it
homogeneous, which is inimical to tablet making. Therefore in case of
the red fat sugar which is used as a vehicle for poisonous medicaments
that require very thorough trituration, it is recommended that the fat
starch be added after the trituration.
The author would suggest that the pharmacist prepare the various fat
sugars described in Chapter VIII and that he keep them on hand, in
a cool and _dark_ place, adding the medicament as prescribed by the
physician, making use of Chapter VII for guidance in the elaboration of
individual formulae.