Proof of the Unmistakable Non Identity and the Comparative Potency of Hyoscine and Scopolamine.
Dr. Wendell Reber of Philadelphia contributes an interesting article upon this subject in The Journal of the American Medical Association for April 25. His paper was read in the Section on Ophthalmology of the American Medical Association at its Atlantic City meeting in June, 1907. For some unexplainable reason this article, which bears so strongly upon the controversy concerning the alleged identity of hyoscine and scopolamine, has been withheld from publication for eleven months. This is of peculiar interest, inasmuch as the editor of the Association Journal during this period has been asserting and reasserting most vociferously through the columns of that journal that these two alkaloids are both chemically and pharmacodynamically identical. Dr. Reber's conclusions, which were based upon careful experimental work made upon human beings, are diametrically opposed to the assertions of Dr. G. H. Simmons, Dr. H. C. Wood, Jr., and others, in The Journal of the American Medical Association and its "anvil chorus."
Dr. Reber follows his experiments, which were quite extended, with an interesting study of the chemistry of hyoscine and allied products derived from the Solanaceous plants. He shows that hyoscine hydrobromide and scopolamine hydrobromide were made official in the third edition of the German Pharmacopeia (under the name of the latter), in which they were asserted to be identical "through the influence of E. Schmidt," the authority most quoted by those asserting the absolute identity of these two alkaloids. Apparently this belief in their identity is a one-man dictum which has been passed from Schmidt to the German Pharmacopeia, and thence over to the makers of the U. S. Pharmacopeia.
To show that this difference in action between hyoscine and scopolamine cannot be due to any difference in the purity of the two products, Dr. Reber quotes his correspondence with Merck & Company, to show that both the hyoscine and scopolamine hydrobromide had a rotatory power of -20. In other words, they are chemically identical, of the same degree of purity, yet pharmacodynamically different.
Dr. Reber says: "This leaves the matter precisely where it was in the beginning, namely: that with two drugs said to be absolutely identical as to clinical effect, pharmacodynamic power, molecular build and reaction with the polariscope, there should seem to be a more or less uniform difference in potency when tested by the delicate accommodation reaction."
"In the last analysis," says Dr. Reber, "it is always the clinical phase of such studies that interests us most." With this we most emphatically agree, since in this important report the claims made by Abbott, verified by many practitioners, concerning the nonidentity of the action of hyoscine and scopolamine are upheld at every point. Dr. Reber shows that hyoscine and scopolamine differ decidedly in their action upon the eye. If the slightest difference of action of these two substances is admitted the whole argument of the J. A M. A. critics of Abbott must break down. Dr. Reber prefers the hyoscine to scopolamine in his refraction work, just as many others prefer hyoscine to scopolamine when the alkaloids are used for anesthetic or analgesic purposes.