This section is from the book "Botanic Drugs Their Materia Medica, Pharmacology and Therapeutics", by Thomas S. Blair. Also available from Amazon: Botanic Drugs, Their Materia Medica, Pharmacology and Therapeutics.
A phenol derived from the volatile oil of Thymus vulgaris, horse-mint and a few other plants. Only that from thyme is designated officially in the U. S. P. Thymus serpyllum. Wild Thyme, and Garden Thyme and Oil of Thyme are widely official.
Thymol is a stearoptene with marked antiseptic properties; it is but slowly absorbed from the alimentary canal. Pharmacologically thymol is intermediate between phenol and oil of turpentine; like phenol, it paralyzes the end-organs of the sensory nerves; if absorbed - combining it with oils, such as castor oil, favors its absorption - it depresses the nerve centers, poisonous doses causing coma and death. Its slight solubility in water - 1:1,500 - limits its usefulness as an antiseptic.
An oil solution of 1:1,000, or one of the same strength in water, with the addition first of a little alcohol to the thymol, is widely used as an antiseptic; and, with other agents, thymol enters into many formulae in surgery. The fact that its odor is attractive to flies limits its usefulness.
As an antiparasitic, a solution of 1:15 in alcohol or ether is used in the treatment of ringworm and pityriasis versicolor. Ointments (10 grains to the ounce) are used in various diseases of the skin. As a mouth wash, the glycerite of thymol (1:200) is available.
The principal use of thymol is in the treatment of hookworm disease, or infestation with the Nercator Americanus or Ankylostoma duodenale. From 1/2 to 1 drachm of thymol, divided in four doses and given in capsules in the course of a day, and followed by a tablespoonful of magnesium sulphate in water, is the approved treatment; but the U. S. P. gives the average anthelmintic dose as 15 grains per day. This large dosage should not be frequently repeated, and castor oil should not be used as the purgative. Allow no oil or alcohol, since thymol is soluble in them.
Oil of chenopodium is coming into use in the place of thymol in the treatment of hookworm disease. See "Chenopodium."
Thymol has been recommended as an internal antiseptic in the treatment of many diseases, but it is not very effective. The average dose is 2 grains.
Thymol Iodide, Aristol, is official in the U. S. P. It is a condensation product of two molecules of thymol with two atoms of iodine, and is dithymol diiodide. An efficient substitute for iodoform, it is a valuable dry surgical dressing; but upon serous membranes it tends to prevent their adhesion. It is contraindicated when secretion is free. It is employed in affections such as lupus, psoriasis, eczema, syphilitic lesions, and in diseased conditions of the mucous membranes. It may be used in oil, ether, flexible collodion, lanolin, or petrolatum. Never heat it, nor mix with alkalies, metallic oxides, or starch.