Hyoscyamus leaves, officially so called (Hyoscyamus, U.S.P.), consist of the fresh leaves, flowering tops, and branches of the biennial variety of Hyoscyamus niger, Linn. (N.O. Solanaceae), and the same parts of the plant carefully dried. The Brussels Conference agreed that the leaves only should be used. Biennial henbane is an erect herb distributed over the whole of Europe, and cultivated in this country for medicinal purposes. The tops and branches are collected while the plant is in full flower. The leaves vary considerably in size; the lower attain as much as 25 centimetres in length, and are stalked, but the upper are smaller and sessile. They are ovate-oblong in shape, sinuate-dentate, or coarsely dentate in outline, and acute at the apex. They are pale green in colour, and clothed on both sides with long soft hairs, many of which secrete a resin, which renders the leaves clammy and sticky to the touch; the midrib is broad and conspicuous. The flowers, which are crowded together, spring from the axils of large hairy bracts, and possess a green, hairy, gamosepalous calyx, and a yellow, purple-veined gamopetalous corolla; they are succeeded by urn-shaped capsular fruits containing numerous minute seeds. The odour is characteristic, the taste bitter and slightly acrid. The broken or powdered leaves may be identified under the microscope by means of the abundance of small prismatic crystals of calcium oxalate contained in the mesophyll, as well as by the long hairs, most of which terminate in a pluricellular secreting gland. When grown in this country the official henbane plant is usually biennial, producing during the first year a rosette of radical leaves, and in the second year an erect branching and flowering plant. The leaves of the first year's growth are collected and sold under the name of "first biennial henbane." This variety consists of large stalked leaves attaining 30 centimetres or more in length, and is, of course, free from flower. Under favourable conditions the biennial plant will flower in the first year; this is also collected and sold as annual (English) henbane. It closely resembles the biennial, but the flowering tops are usually less dense, and the drug often contains portions of the stem. All these three varieties appear to be of good quality and of equal alkaloidal value. On incineration about 12 per cent. of ash is obtained. Much henbane is imported from the South of Europe; this is probably collected mostly from annual plants. Foreign annual henbane is usually a much more slender plant than the English, more stalky, and often badly preserved. Its alkaloidal value, 0.03 per cent., is lower than that of any of the English-grown varieties. This may be due to the large proportion of stem, sand, etc., that the drug contains, and it is probable that the well-dried leaves alone of all the varieties are of approximately equal alkaloidal strength.
Constituents.—The chief constituent from henbane leaves is the alkaloid hyoscyamine, together with smaller quantities of atropine and hyoscine (scopolamine). The proportion of alkaloid in the B.P. dried drug varies from 0.045 to 0.14 per cent. In isolated cases larger yields of alkaloid (up to 0.27 per cent.) have been reported, but these are exceptional. Hyoscyamus, U.S.P., should contain not less than 0.08 per cent. of mydriatic alkaloids.
Action and Uses.—Hyoscyamus is a cerebral and spinal sedative, due to the hyoscyamine and hyoscine (scopolamine) which it contains. The comparatively small amount of atropine present does not give rise to the excitation and delirium occasioned by belladonna. It is therefore used in insomnia, especially when opium cannot be given; except for this difference it acts like atropine. Hyoscyamus is used to relieve the griping caused by drastic purgatives; exactly how it acts is not known, but it acts without diminishing the peristalsis; it is a common ingredient of aperient pills, especially those containing aloes and colocynth. It is given to allay irritability of the bladder and relieve pain in cystitis, and acts in precisely the same way as atropine. The tincture is given in mixtures as an antispasmodic in asthma in place of stramonium. For this purpose Succus Hyoscyami is sometimes preferred. A sedative application for external use, known as "Oleum Hyoscyami Infusum," is prepared by macerating henbane leaves in alcohol, mixing the strong tincture with olive oil, and heating on a water-bath until the alcohol is dissipated. This preparation should be distinguished from the fixed oil obtained by expression from the seeds.
Dose.—2 to 6 decigrams (3 to 10 grains).
- Extractum Hyoscyami, P.I.—EXTRACT OF HYOSCYAMUS, P.I.
- A solid extract, containing about 10 per cent, of water, prepared with alcohol (70 per cent.).
- Extractum Hyoscyami, U.S.P.—EXTRACT OF HYOSCYAMUS.
- The fluidextract is evaporated to a pilular consistence, and made to contain 0.3 per cent. of mydriatic alkaloids. Average dose.—65 milligrams (1 grain).
- Extractum Hyoscyami Exsiccatum, B.P.C.—DRIED EXTRACT OF HYOSCYAMUS. Syns.—Extractum Hyoscyami Foliorum Exsiccatum; Dried Extract of Hyoscyamus Leaves.
- Contains 0.2 per cent. of alkaloid. It is an improvement upon the official green extract. It is constant in strength, and being in the form of powder is more convenient for dispensing. It should be kept in a cool, dry place. Dose.—1 to 3 decigrams (2 to 5 grains).
- Extractum Hyoscyami Viride, B.P.—GREEN EXTRACT OF HYOSCYAMUS. Syn.—Extract of Henbane.
- Express the juice from the bruised leaves, flowering tops, and young branches of hyoscyamus, and gradually heat to 54°; strain through calico to remove the chlorophyll, heat the strained liquid to 93°, and filter. Evaporate the filtrate to a thin syrup, add the chlorophyll after passing it through a hair sieve; mix, and evaporate to a soft extract at a temperature not exceeding 60°. The alkaloidal strength of green extract of henbane varies from 0.15 to 0.45 per cent., the average strength being about 0.2 per cent. This extract is very commonly used in pills to allay the griping of purgatives (as in Pilula Colocynthidis et Hyoscyami), and for its sedative properties. It is occasionally ordered in suppositories, when the extract should be rubbed to a smooth paste with a few drops of water before incorporating with the fat melted at a low temperature. Dose.—1 to 5 decigrams (2 to 8 grains).
- Fluidextractum Hyoscyami, U.S.P.—FLUIDEXTRACT OF HYOSCYAMUS.
- Hyoscyamus, in No. 60 powder, 100; alcohol (63 per cent.), sufficient to produce about 100. The product is assayed, and made to contain 0.075 per cent. w/v of alkaloids. Average dose.—2 decimils (3 minims).
- Succus Hyoscyami, B.P.—HYOSCYAMUS JUICE.
- Hyoscyamus juice is prepared by subjecting the bruised, fresh leaves, flowering tops, and young branches of Hyoscyamus niger, Linn., to pressure, adding to the expressed juice one-third its volume of alcohol, allowing the mixture to stand for seven days, and filtering. It is of fairly constant strength, approximating to 0.005 per cent. of total alkaloids. Dose.—2 to 4 mils (1/2 to 1 fluid drachm).
- Tinctura Hyoscyami, B.P.—TINCTURE OF HYOSCYAMUS. Synonym.—Tincture of Henbane,
- Hyoscyamus leaves and flowering tops, in No. 20 powder, 10; alcohol (45 per cent.), sufficient to produce 100. Add 10 of the alcohol to the drug to moisten it, and proceed with the percolation process. Tincture of hyoscyamus is used in the same way as tincture of belladonna, but is more sedative on account of the hyoscine it contains. It is employed to allay irritability of the bladder and to prevent griping by purgative medicines. It is also used in all spasmodic affections of plain muscle. Dose.—2 to 4 mils (1/2 to 1 fluid drachm).
- Tinctura Hyoscyami, P.I.—TINCTURE OF HYOSCYAMUS, P.I.
- Strength, 10 per cent. Prepared by percolation with alcohol (70 per cent.).
- Tinctura Hyoscyami, U.S.P.—Similar to B.P., but made with alcohol (49 percent.), and standardised to contain 0.007 per cent. w/v of alkaloids.
- Average dose.—2 mils (30 minims).
The British Pharmaceutical Codex, 1911, was published by direction of the Council of the Pharmaceutical Society of Great Britain.