This section is from the book "A Treatise On Therapeutics, And Pharmacology Or Materia Medica Vol1", by George B. Wood. Also available from Amazon: Part 1 and Part 2.
Neither generally nor locally should henbane be administered with one of the fixed caustic alkalies; and, when it is desirable to combine an alkaline action with that of the medicine, the carbonates should be used. The medicine may be given in substance, extract, or tincture. The dried leaves are so uncertain that they are very seldom used. The dose to begin with is from five to ten grains. The seeds should not be employed at first in more than half the smaller dose mentioned. The extract is much more frequently used.
Two extracts of henbane are directed by our national Pharmacopoeia, one made by inspissating the expressed juice of the fresh leaves, the other by evaporating an alcoholic tincture of the dried leaves The former is called simply Extract of Henbane (Extractum Hyoscyami, U. S.), the latter Alcoholic Extract of Henbane (Extractum Hyoscyami Alco-holicum, U. S.). As, in many parts of our country, the fresh leaves cannot be obtained, it is necessary either to use the imported extract, or to prepare the alcoholic. Unhappily, in either case, the preparation is of very uncertain strength, and often extremely feeble. The proper method of proceeding, in this uncertainty, is to give from one to three grains of the extract, and gradually increase the dose until it produces the desired effect, or at least evinces some narcotic power; and, having thus ascertained the strength of the parcel, to be guided afterwards accordingly. The dose will often be raised to ten grains before acting, sometimes even to twenty or thirty grains, or indeed much higher; for occasionally the extract is quite inert.
A Fluid Extract (Extractum Hyoscyami Fluidum, U. S.) was introduced into the U. S. Pharmacopoeia at the late revision. It is a concentrated tincture, and may be given in the commencing dose of from five to ten minims.
The Tincture of Henbane (Tinctura Hyoscyami, U. S., Br.) is also officinal. It is prepared from the leaves by percolation with diluted alcohol, and is of such a strength that a fluidrachm represents rather less than eight grains. The same rule holds as to the commencing dose in this as in the extract; for the preparation is almost equally uncertain. From thirty minims to a fluidrachm and a half may be given at first.
Should hyoscyamia be used, not more than one-sixteenth of a grain should be given at once. As water dissolves it in small proportion, its aqueous solution may be used for dilating the pupil, being for that purpose dropped into the eye.