Terpin hydrate

Terpin hydrate is an expectorant, commonly used to loosen mucus in the setting of acute or chronic bronchitis, and related conditions. It is derived from sources such as oil of turpentine, oregano, thyme and eucalyptus. Though it was quite popular in the USA since the late nineteenth century, it was banned by the U.S. Food and Drug Administration (FDA) in the 1990s due to lack of proof of efficacy.

History
Terpin hydrate was first physiologically investigated by Lepine in 1855. He reported that it acted upon the mucous membranes and also the nervous system in a manner similar to the oil of turpentine.

The following preparations of Terpin hydrate were available in the USA in 1907 (Taken from The Dispensatory Of The United States Of America. Nineteenth Edition. By Dr. Geo. B.Wood And Dr. Franklin Bache. Based Upon The Eighth Decennial Revision Of The United States Pharmacopoeia Issued June 1, 1907):
 * Elixir of Terpin Hydrate
 * Elixir of Terpin Hydrate with Codeine
 * Elixir of Terpin Hydrate with Heroin

Uses
Terpin hydrate is an expectorant, commonly used in the treatment of acute and chronic bronchitis. It is commonly formulated with an antitussive (e.g., codeine) as a combined preparation.

Pharmacologic mechanisms of action
A humectant and expectorant, terpin hydrate works directly on the bronchial secretory cells in the lower respiratory tract to liquefy and facilitate the elimination of bronchial secretions. It also exerts a weak antiseptic effect on the pulmonary parenchyma.

Indications
The preparation is used in acute and chronic bronchitis; pneumonia; bronchiectases; chronic obstructive pulmonary disease; infectious and inflammatory diseases of the upper respiratory tract.

Dosage and administration
The recommended dose is 85 to 170 milligrams, 3 or 4 times daily.

Adverse reactions
depression of the respiration, sedation, coordination disorders, constipation, urinary retention. Long-term administration of the preparation leads to drug dependence (codeine-dependence).

The side effects of this drug are related to its high alcohol content (42 percent). If enough ETH is consumed it will produce significant CNS depression.

Currently available expectorants in the USA
Currently, guaifenesin (Glyceryl Guaiacolate) is the only agent approved by the FDA for use as an expectorant in the USA. Formerly used expectorants like ammonium chloride, beechwood creosote, benzoin preparations, camphor, eucalyptol/eucalyptus oil, iodines, ipecac syrup, menthol/peppermint oil, pine tar preparations, potassium guaiacolsulfonate, sodium citrate, squill preparations, terpin hydrate, tolu and turpentine oil, must be reformulated.