Peppermint consists of the dried leaves and flowering tops of Mentha piperita, Smith (N.O. Labiatae), a plant found growing wild throughout Europe, and cultivated in England, France, Germany, Russia, and America. There are two varieties, known respectively as black and white peppermint. The drug is official in the U.S.P. The stems are quadrangular, with scattered, deflexed hairs and petiolate, ovate-lanceolate, light or dark green leaves, 3 to 8 centimetres long, acute, and sharply serrate; the small purple flowers occur in terminal obtuse spikes arranged in whorls, with five-toothed tubular calyx, four-lobed corolla, and four short, equal stamens. Odour, strong and characteristic; taste, pungent and cooling.
Constituents.—The chief constituent of peppermint is the volatile oil (see Oleum Menthae Piperitae).
Action and Uses.—Peppermint acts as an aromatic stimulant and carminative and is used chiefly in the form of the oil, but the drug is an ingredient of Spiritus Menthae Piperitae, U.S.P.
Dose.—2 to 4 grammes (30 to 60 grains).
C10H20O = 156.16.
Menthol, C6H90HCH3C3H7, is a saturated secondary alcohol, found only in the laevogyrate modification, as the principal constituent of peppermint oils obtained from various species of Mentha, and imported into England chiefly from Japan. It is also official in the U.S.P. The oils from which it is chiefly obtained are those from Mentha arvensis, var. piperascens, in Japan; var. glabrata, in China; and Mentha piperita, in America. It is separated from the oils by freezing. It occurs in colourless, acicular or prismatic crystals belonging to the hexagonal system, more or less moist from adhering oil; brittle, and having a strong odour of peppermint, and a warm aromatic taste followed by a sensation of cold on drawing air into the mouth. Melting-point, 43°, at which temperature it is a colourless liquid; boiling-point, 212°; specific gravity, about 0.890. Water with which it has been shaken acquires the characteristic odour and taste. Alcoholic and other solutions are neutral to litmus. It volatilises slowly at ordinary temperatures; heated in an open dish on a water-bath it volatilises without leaving any residue (absence of magnesium sulphate, wax, paraffin, etc.). In contact with thymol, camphor, etc., it liquefies. If a few crystals be dissolved in 1 mil of glacial acetic acid, and 3 drops of sulphuric acid and 1 drop of nitric acid be added, no green colour should be developed (absence of thymol). When menthol is oxidised with chromic acid mixture, the laevogyre ketone, C10H18O (menthone), is produced. When dehydrated by means of zinc chloride or potassium acid sulphate, menthol is converted into menthene (C10H18). Heated with anhydrous copper sulphate to 250° to 280°, menthol yields cymene. A derivative by means of which menthol is easily characterised is the menthyl benzoate, produced by heating it with benzoic anhydride; the ester melts at 54.5°, and is with difficulty volatilised with water vapour.
Almost insoluble in water and in glycerin; soluble in alcohol (5 in 1), ether (8 in 3), chloroform (about 4 in 1), liquid paraffin (1 in 6), petroleum spirit (10 in 7), olive oil (1 in 4), and in ethereal oils.
Action and Uses.—Menthol is used internally as a stimulant and carminative in flatulence and gastralgia, either made into a pill, or dissolved in oil and enclosed in a gelatin capsule. It resembles oil of peppermint in its action, but is more powerful, and more liable to upset digestion. It exerts an anaesthetic effect in the stomach, owing to its action on sensory nerve endings, and to this is attributed its beneficial action in seasickness. Pills are best prepared by adding a little soap and massing with syrup of glucose. If camphor, carbolic acid, or other liquefying substance be present, kieselguhr should be added as an absorbent, and the same process followed. Externally, it is employed as a local analgesic. Rubbed on the skin, it produces a sensation of cold, followed by numbness and partial anaesthesia; it first stimulates the nerves, conveying the sensation of cold, and later penetrates the skin and paralyses the terminations of the ordinary sensory nerves. Menthol moulded into cones is rubbed over neuralgic areas to allay pain. Its action is more complete when dissolved in chloroform, the solution being applied with a brush. Linimentum Mentholis is such a preparation, and is used in neuralgia, sciatica, and lumbago. Menthol, when dissolved in oleic acid, is readily absorbed from the skin; a solution of menthol, 200 grains, in 4 fluid drachms of oleic acid is known as "Mentholeate," and is used in neuralgia, pruritus, etc. Menthol is much used as an inhalation or application to the nasopharyngeal and laryngeal mucous membranes. Mixed with camphor and oil of eucalyptus it is inhaled from cotton wool, or with steam from hot water, for the relief of catarrhs; or the vapour may be inhaled by drawing air through a tube containing the crystals. It is a common ingredient of snuffs for use in nasal catarrh (see Insufflatio Mentholis), and is also much used in the form of pastille. It is used in oily solution (1 or 2 per cent.) applied by means of a spray, and in this form menthol soothes the irritation of catarrh, arrests sneezing, and relieves the sense of fulness in the head. Strong alcoholic solutions of menthol are precipitated on the addition of water. When menthol is required in an aqueous medium, Aqua Mentholis, which is a saturated solution, should be used. Emplastrum Mentholis is applied in rheumatism and lumbago. Menthol ointment (1 per cent. in soft paraffin) is applied to the nares in coryza; a stronger ointment (1 in 20) is applied in neuralgia. Liquefying mixtures of equal weights of menthol and chloral hydrate or camphor are applied on cotton wool to carious teeth to relieve pain. A solution of menthol in olive oil (1 in 4) is used as a paint for the larynx in tuberculous ulceration. Compound menthol wool (Gossypium Mentholis Compositum) is used for nasal catarrh, hay fever, etc., small pieces being inserted loosely in the nostrils. Various esters of menthol have been prepared, and are usually known under trade-names. Coryfin is menthol ethylglycollate, a colourless liquid, insoluble in water, soluble in alcohol and oils. It is used as a paint to the nostrils or by inhalation from hot water. Internally it is given in doses of 1 to 3 decimils (0.1 to 0.3 milliliters) (2 to 5 minims). Estoral is a compound of menthol with boric acid. Validol, a solution of menthol in menthyl valerianate, is a colourless liquid, insoluble in water, soluble in alcohol; used as a carminative in vomiting, and especially recommended in seasickness, and also employed in hysteria. Dose, 6 to 10 decimils (0.6 to 1.0 milliliters) (10 to 15 minims). Menthol liquefies with butyl-chloral hydrate, camphor, carbolic acid, chloral hydrate, naphthol, resorcin, or thymol.
Dose.—3 to 12 centigrams (1/2 to 2 grains).
- Aqua Mentholis, B.P.C.—MENTHOL WATER.
- A saturated solution of menthol in water, employed as a vehicle for alkaline and antiseptic solutions for the throat and nose. It may also be used as a carminative and antispasmodic in place of peppermint water. Dose.—15 to 30 mils (1/2 to 1 fluid ounce).
- Emplastrum Menthol, B.P.—MENTHOL PLASTER. Syn.—Emplastrum Mentholis.
- Menthol, 15; yellow beeswax, 10; resin, 75. Melt together the beeswax and resin, and dissolve the menthol in the mixture at a temperature between 71° and 77°. Menthol plaster is used in neuralgia, rheumatism, and lumbago.
- Gossypium Mentholis, B.P.C.—MENTHOL WOOL. 10 per cent.
- This preparation should be preserved in well-closed vessels. Used in coryza.
- Gossypium Mentholis Compositum, B.P.C.—COMPOUND MENTHOL WOOL.
- Menthol, 3.5; formaldehyde solution, 3; oil of lavender, 3; oil of eucalyptus, 3; alcohol, to 100; absorbent cotton, compressed, a sufficient quantity. Used for nasal catarrh, hay fever, etc., a small piece being inserted loosely in each nostril, and replaced at intervals of about an hour.
- Insufflatio Mentholis, B.P.C.—MENTHOL SNUFF.
- Menthol, 1; ammonium chloride, 9: boric acid, 10. Used as snuff, in nasal catarrh.
- Insufflatio Mentholis Composita, B.P.C.—COMPOUND MENTHOL SNUFF.
- Menthol, 5; ammonium chloride, 10; boric acid, 20; lycopodium, 65. Used as a snuff in nasal catarrh and hay fever.
- Insufflatio Mentholis et Cocainae, B.P.C.—MENTHOL AND COCAINE SNUFF.
- Menthol, 2.5; cocaine hydrochloride, 0.15; ammonium chloride, 25; camphor, 5; lycopodium, to 100. Used as a snuff, in coryza.
- Linimentum Mentholis, B.P.C.—MENTHOL LINIMENT.
- Menthol, 20; chloroform, 25; olive oil, to 100. Painted on the skin or applied on lint for neuralgia, sciatica, and lumbago.
- Nebula Mentholis, B.P.C.—MENTHOL SPRAY. Syn.—Pigmentum Mentholis. 1 in 20.
- Used as an antiseptic in nasal catarrh, and to check excessive discharge.
- Nebula Mentholis Aetherea, B.P.C.— ETHEREAL MENTHOL SPRAY.
- Menthol, 4; chloroform, 40; ether, to 100. Used to produce temporary local anaesthesia.
- Nebula Mentholis Composita, B.P.C.—COMPOUND MENTHOL SPRAY.
- Menthol, 3; cocaine hydrochloride, 0.5; tincture of benzoin, 50; glycerin, to 100. Used with a nebuliser for its antiseptic and sedative properties in laryngitis, asthma, and bronchitis.
- Nebula Mentholis et Cocainae, B.P.C.—MENTHOL AND COCAINE SPRAY.
- Menthol, 5; cocaine, 2; almond oil, 25; liquid paraffin, to 100. Used for the throat and nose in pharyngitis and catarrhal colds.
- Nebula Mentholis et Iodi Composita, B.P.C.—COMPOUND MENTHOL AND IODINE SPRAY.
- Iodine, 0.5; compound menthol and thymol spray, to 100.
- Nebula Mentholis et Thymolis Composita, B.P.C.—COMPOUND MENTHOL AND THYMOL SPRAY.
- Menthol, 2; thymol, 2; camphor, 2; phenol, 2; liquid paraffin, to 100.
- Parogenum Mentholis, B.P.C.—MENTHOL PAROGEN. Syn.—Menthol Vasoliment.
- Menthol, 2; parogen, to 100. Applied to the seat of pain in neuralgia, sciatica, lumbago, etc.
- Pastillus Mentholis, B.P.C.—MENTHOL PASTILLE. 1/20 grain.
- Pastillus Mentholis et Cocainae, B.P.C.—MENTHOL AND COCAINE PASTILLE.
- Each pastille contains menthol, 3 milligrams (1/20 grain); cocaine hydrochloride, 3 milligrams (1/20 grain).
- Pastillus Mentholis et Codeinae, B.P.C.—MENTHOL AND CODEINE PASTILLE.
- Each pastille contains menthol, 3 milligrams (1/20 grain); codeine phosphate, 6 milligrams (1/10 grain).
- Pastillus Mentholis et Eucalyptolis, B.P.C.—MENTHOL AND EUCALYPTOL PASTILLE.
- Each pastille contains menthol, 3 milligrams (1/20 grain); eucalyptol, 3 centimils (0.03 milliliters) (1 minim).
- Pigmentum Mentholis Compositum, B.P.C.— COMPOUND MENTHOL PAINT.
- Menthol, 0.25; thymol, 0.25; oil of eucalyptus, 12.5; liquid paraffin, to 100. Applied with a brush to the nasal mucous membrane for hay fever and catarrh.
- Pigmentum Mentholis et Tolueni, B.P.C.—MENTHOL AND TOLUENE PAINT. Syn.—Löffler's Pigment or Solution.
- Menthol, 10; absolute alcohol, 60; strong solution of ferric chloride, 1; toluene, 100. Applied as an antiseptic to the false membrane of diphtheria.
- Spiritus Mentholis, B.P.C.—SPIRIT OF MENTHOL. 1 in 20.
- Tabellae Mentholis, B.P.C.—MENTHOL TABLETS. 1/5 grain.
- Trochisci Mentholis Compositi, B.P.C.—COMPOUND MENTHOL LOZENGES.
- Each lozenge contains 1/4 grain of menthol, 3/4 grain of potassium chlorate, 1/40 grain betacaine hydrochloride, with a sufficient quantity of fruit basis. Compound menthol lozenges are used in catarrh and in ulcerated and inflamed conditions of the buccal mucous membrane.
- Unguentum Mentholis et Cocainae, B.P.C.—MENTHOL AND COCAINE OINTMENT.
- Menthol, 10; cocaine, 10; soft paraffin, white, 80.
The British Pharmaceutical Codex, 1911, was published by direction of the Council of the Pharmaceutical Society of Great Britain.