Terpin hydrate is an expectorant, commonly used to loosen mucus

Mucus

In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. Mucous fluid is typically produced from mucous cells found in mucous glands. Mucous cells secrete products that are rich in glycoproteins and water. Mucous fluid may also originate from mixed glands, which...

 in the setting of acute

Acute (medicine)

In medicine, an acute disease is a disease with either or both of:# a rapid onset, as in acute infection# a short course ....

 or chronic

Chronic (medicine)

A chronic disease is a disease or other human health condition that is persistent or long-lasting in nature. The term chronic is usually applied when the course of the disease lasts for more than three months. Common chronic diseases include asthma, cancer, diabetes and HIV/AIDS.In medicine, the...

 bronchitis

Bronchitis

Acute bronchitis is an inflammation of the large bronchi in the lungs that is usually caused by viruses or bacteria and may last several days or weeks. Characteristic symptoms include cough, sputum production, and shortness of breath and wheezing related to the obstruction of the inflamed airways...

, and related conditions. It is derived from sources such as oil of turpentine

Turpentine

Turpentine is a fluid obtained by the distillation of resin obtained from trees, mainly pine trees. It is composed of terpenes, mainly the monoterpenes alpha-pinene and beta-pinene...

, oregano

Oregano

Oregano – scientifically named Origanum vulgare by Carolus Linnaeus – is a common species of Origanum, a genus of the mint family . It is native to warm-temperate western and southwestern Eurasia and the Mediterranean region.Oregano is a perennial herb, growing from 20–80 cm tall,...

, thyme

Thyme

Thyme is a culinary and medicinal herb of the genus Thymus.-History:Ancient Egyptians used thyme for embalming. The ancient Greeks used it in their baths and burnt it as incense in their temples, believing it was a source of courage...

 and eucalyptus

Eucalyptus

Eucalyptus is a diverse genus of flowering trees in the myrtle family, Myrtaceae. Members of the genus dominate the tree flora of Australia...

. 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 alleged lack of proof of efficacy.

History

Terpin hydrate was first physiologically investigated by Lepine

Lepine

-People:* Alfred Lépine , Canadian ice hockey player* Ambroise-Dydime Lépine , Canadian aboriginal leader* Hector Lepine , Canadian ice hockey player* Jean-Antoine Lépine , French clock and watchmaker...

 in 1855. He reported that it acted upon the mucous membrane

Mucous membrane

The mucous membranes are linings of mostly endodermal origin, covered in epithelium, which are involved in absorption and secretion. They line cavities that are exposed to the external environment and internal organs...

s and also the nervous system

Nervous system

The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of its body. In most animals the nervous system consists of two parts, central and peripheral. The central nervous...

 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
  Codeine
  Codeine or 3-methylmorphine is an opiate used for its analgesic, antitussive, and antidiarrheal properties...
  
  
• 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

Humectant

A humectant is a hygroscopic substance. It is often a molecule with several hydrophilic groups, most often hydroxyl groups, but amines and carboxyl groups, sometimes esterified, can be encountered as well; the affinity to form hydrogen bonds with molecules of water is crucial here.Since...

 and expectorant, terpin hydrate works directly on the bronchial secretory cells in the lower respiratory tract

Lower respiratory tract

The term lower respiratory tract refers to the portions of the respiratory system from the trachea to the lungs.Lower respiratory tract infections can be the cause of several serious illnesses, including pneumonia....

 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.

Adverse reactions

Adverse reactions include depression of the respiration, sedation, coordination disorders, constipation, and urinary retention.

Long-term administration of the popular combination product of Terpin hydrate with codeine may lead to codeine dependence. Terpin hydrate with codeine is often mixed with alcohol as this combination is not as readily as soluble in water. This combination can also cause complications and problems of cross dependence with alcohol and codeine as well as increase codeine metabolism and side-effects.

The side effects of this combination product 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

Guaifenesin

Guaifenesin INN or guaiphenesin , also glyceryl guaiacolate, is an expectorant drug sold over the counter and usually taken by mouth to assist the bringing up of phlegm from the airways in acute respiratory tract infections.-History:Similar medicines derived from the guaiac tree were in use as a...

 (Glyceryl Guaiacolate) is the only agent approved by the FDA for use as an expectorant in the USA. Formerly used expectorants like ammonium chloride

Ammonium chloride

Ammonium chloride NH4Cl is an inorganic compound with the formula NH4Cl. It is a white crystalline salt that is highly soluble in water. Solutions of ammonium chloride are mildly acidic. Sal ammoniac is a name of natural, mineralogical form of ammonium chloride...

, beechwood creosote

Creosote

Creosote is the portion of chemical products obtained by the distillation of a tar that remains heavier than water, notably useful for its anti-septic and preservative properties...

, benzoin

Benzoin

Benzoin is an organic compound with the formula PhCHCPh. It is a hydroxy ketone attached to two phenyl groups. It appears as off-white crystals, with a light camphor-like odor. Benzoin is synthesized from benzaldehyde in the benzoin condensation...

 preparations, camphor

Camphor

Camphor is a waxy, white or transparent solid with a strong, aromatic odor. It is a terpenoid with the chemical formula C10H16O. It is found in wood of the camphor laurel , a large evergreen tree found in Asia and also of Dryobalanops aromatica, a giant of the Bornean forests...

, eucalyptol/eucalyptus oil

Eucalyptus oil

Eucalyptus oil is the generic name for distilled oil from the leaf of Eucalyptus, a genus of the plant family Myrtaceae native to Australia and cultivated worldwide. Eucalyptus oil has a history of wide application, as a pharmaceutical, antiseptic, repellent, flavouring, fragrance and industrial uses...

, iodine

Iodine

Iodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....

s, ipecac syrup, menthol

Menthol

Menthol is an organic compound made synthetically or obtained from peppermint or other mint oils. It is a waxy, crystalline substance, clear or white in color, which is solid at room temperature and melts slightly above. The main form of menthol occurring in nature is -menthol, which is assigned...

/peppermint oil, pine tar

Pine tar

Pine tar is a sticky material produced by the high temperature carbonization of pine wood in anoxic conditions . The wood is rapidly decomposed by applying heat and pressure in a closed container; the primary resulting products are charcoal and pine tar.Pine tar consists primarily of aromatic...

 preparations, potassium guaiacolsulfonate, sodium citrate

Sodium citrate

Trisodium citrate has the chemical formula of Na3C6H5O7. It is sometimes referred to simply as sodium citrate, though sodium citrate can refer to any of the three sodium salts of citric acid. It possesses a saline, mildly tart flavor. For this reason, citrates of certain alkaline and alkaline earth...

, squill preparations, terpin hydrate, tolu

Tolú

Tolú is a small town and municipality in Sucre Department, northern Colombia by the Caribbean sea. The municipality has an area of 500 km². The name of Tolú comes from a tree called the Balsam of Tolú....

and turpentine oil, must be reformulated.