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OBSERVATIONS ON THE STRENGTH OF TINCTURE OF OPIUM. BY A. B. GARROD, M. D.
Professor of Materia Medica at University College, and Physician to University College Hospital.
As many discrepant statements are to be found in works on Materia Medica, in various dispensatories, &c. concerning the strength of the tincture of opium of the London Pharmacopœia, it may not be either uninstructive or uninteresting at least to the medical profession, to have the subject brought under notice and discussion at this society, in order that they may arrive at some definite conclusion concerning the strength of a preparation they are in the daily habit of prescribing. If we refer to the London Pharmacopœia of 1836, we find the following directions for making the tincture of opium:—
- Take of hard opium powdered, 3 ounces,
- Proof spirit, 2 pints,
- Macerate for fourteen days, and strain.
In the Pharmacopœia of 1851, we are ordered to—
- Take of opium powdered, 3 ounces,
- Proof spirit, 2 pints,
- Macerate for seven days, press out, and strain.
The only difference in the directions being that powdered hard opium, and digestion for fourteen days, are ordered in the one case, and simply powdered opium and seven days digestion in the other. If we look at the authorised edition of the Pharmacopœia by Mr. Philips of 1836, (and also at the present edition) we find stated, that the preparation has a deep brownish red color, possesses the peculiar odor and taste of opium, has sp. gr. 0.952, and about 19 minims contain 1 grain of opium, which is said to be proved by the following data: 1st, by evaporating the tincture, and finding the amount of solid extract left; 2d, by ascertaining the quantity of opium remaining undissolved. The conclusion at which Mr. Phillips arrived, viz: that 1 grain of opium was contained in 19 minims of the Pharmacopœia tincture, has been copied into most English works on Materia {86} Medica, and most medical men have been and are still in the habit of prescribing the tincture considering it to be of the above strength. Were Mr. Phillip’s conclusions correct?
With regard to the amount of solid extract left on evaporation of the tincture, it appears from the experiments of Mr. Allchin, which are also confirmed by those which I have myself made, that 19 minims yield about 1 grain of extract; but in these cases the Turkey opium of commerce must be first exsiccated; and the tinctures of commerce yield quantities varying from 1 in 19 to 1 in 28 minims of the tincture. Tincture of opium made with Turkey opium in small masses not previously dried, fl.
