Ammonium Carbonate

Rarely prescribed in powders, but if so wrap in waxed paper.

Antipyrin (Phenazone)

This substance is eminently a remedy which should be prescribed by itself, unless for physiological reasons a little caffeine is added to counteract heart symptoms. Prescribers go more upon their personal experience than physiological experiments, and combine things with antipyrin which sometimes trouble the dispenser, as in the following instances:

I.

Antipyrin.....................

gr. x.

Sodii salicylatis..............

gr. xx.

Fiat pulvis. Mitte xij.

Sig.: One every four hours.

II.

Phenazoni........................

gr. v.

Caffeinae citratis..............

gr. v.

Sodii nitritis ....................

gr. iss.

Fiat pulvis. Mitte tales vj.

Antipyrin and sodium salicylate liquefy when mixed together, salicylate of antipyrin being formed. This is not at all dependent upon external moisture, therefore wrapping in waxed paper does not obviate it. A dispenser reported that No. I. powders had been dispensed dry: in that case antipyrin salicylate (salipyrin) had been given. The substitution may be suggested to the prescriber; it would be wrong to adopt it in such a case as the above, because salipyrin contains less than half its weight of salicylic acid. The second prescription furnishes a powder which becomes green and finally red. This is due to the moisture in the ingredients, especially in the sodium nitrite, liberating citric acid from the caffeine citrate (an unstable salt). The acid, reacting with the nitrite, liberates nitrous acid, which then, acting upon the phenazone, forms an isonitroso compound of a green colour. With an equivalent of the alkaloid caffeine (2 1/2 grains) this change does not take place, but a dispenser who used parchment-paper for wrapping the powders made with the alkaloid found that they did become green.

This was owing to the parchment-paper being acid in reaction (it is made by steeping ordinary paper in sulphuric acid and water).

Boric Acid and sodium salicylate become pasty when mixed together, owing to the formation of sodium boro-salicylate.

Crystals should be reduced to powder before they are dispensed as powders. In the case of quinine sulphate this is, unfortunately, not generally done 5 but every dispenser who gets a prescription for quinine powders fresh from the prescriber should take care to mark it 'Tere bene i.m.'for the benefit of subsequent dispensers.