Terpin

{{Short description|Chemical compound}} {{confuse|Terpene}} {{Infobox drug | IUPAC_name = 4-(2-Hydroxypropan-2-yl)-1-methylcyclohexan-1-ol | image = Terpin.png | image_class = skin-invert-image | width = 100px | alt = | caption = <!-- Clinical data --> | pronounce = | tradename = | Drugs.com = | MedlinePlus = | pregnancy_AU = <!-- A/B1/B2/B3/C/D/X --> | pregnancy_AU_comment = | pregnancy_US = <!-- A/B/C/D/X/N --> | pregnancy_category = | routes_of_administration = | legal_AU = <!-- S2, S3, S4, S5, S6, S7, S8, S9 or Unscheduled--> | legal_AU_comment = | legal_CA = <!-- OTC, Rx-only, Schedule I, II, III, IV, V, VI, VII, VIII --> | legal_DE = <!-- Anlage I, II, III --> | legal_NZ = <!-- Class A, B, C --> | legal_UK = <!-- GSL, P, POM, CD, CD Lic, CD POM, CD No Reg POM, CD (Benz) POM, CD (Anab) POM or CD Inv POM / Class A, B, C --> | legal_US = <!-- OTC/Rx-only/Schedule I, II, III, IV, V --> | legal_UN = <!-- N I, II, III, IV / P I, II, III, IV--> | legal_status = <!-- Free text --> <!-- Pharmacokinetic data -->| bioavailability = | protein_bound = | metabolism = | metabolites = | onset = | elimination_half-life = | duration_of_action = | excretion = <!-- Identifiers --> | CAS_number_Ref = {{cascite|correct|CAS}} | CAS_number = 565-48-0 | class = | ATCvet = | ATC_prefix = None | ATC_suffix = | PubChem = 6651 | DrugBank = | ChemSpiderID = 6399 | ChEMBL = 1651998 | UNII = MPF495B08R | synonyms = Dipenteneglycol, p-menthane-1,8-diol <!-- Chemical and physical data -->| chemical_formula = | C = 10 | H = 20 | O = 2 | molecular_weight = | smiles = CC1(CCC(CC1)C(C)(C)O)O | StdInChI = 1S/C10H20O2/c1-9(2,11)8-4-6-10(3,12)7-5-8/h8,11-12H,4-7H2,1-3H3 | StdInChIKey = RBNWAMSGVWEHFP-UHFFFAOYSA-N }}

'''Terpin''' is an expectorant, used to loosen mucus in patients with bronchitis and related conditions. It is used as the hydrate (terpin·H₂O). It is derived from sources such as turpentine, oregano, thyme, and eucalyptus. It was used in the United States in the late nineteenth century, but was removed from marketed medications in the 1990s after the Food and Drug Administration (FDA) found a lack of evidence of safety and effectiveness.<ref name=FDA>United States Food and Drug Administration: [https://web.archive.org/web/20030915182250/http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?FR=310.545 Code of Federal Regulations, Title 21, Volume 5, April 1, 2009]</ref> Elixirs of terpin hydrate are still available with a prescription, but must be prepared by a compounding pharmacy.

It can be prepared from other volatile oils like geraniol and linalool by adding dilute acids (5% sulfuric acid) to them.<ref>{{cite journal | vauthors = Perkin WH | title = LXVI.—Experiments on the synthesis of the terpenes. Part I. Synthesis of terpin, inactive terpineol, and dipentene. | journal = Journal of the Chemical Society, Transactions | date = 1904 | volume = 85 | pages = 654–671 | doi = 10.1039/CT9048500654 }}</ref>

==Medical uses== Terpin hydrate is an expectorant, used in the treatment of acute and chronic bronchitis, pneumonia, bronchiectasis, chronic obstructive pulmonary disease, and infectious and inflammatory diseases of the upper respiratory tract. It is typically formulated with an antitussive, such as codeine, as a combined preparation.

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

Long-term administration of the combination product of terpin hydrate with codeine may lead to codeine dependence. Terpin hydrate with codeine is often mixed with alcohol as codeine is not as readily as soluble in water. The high alcohol content (42 percent) may increase depression of the central nervous system, codeine metabolism, as well as abuse potential.{{Citation needed|date=February 2017}}

==Mechanism of action== A humectant and expectorant, terpin hydrate works directly on the bronchial secretory cells in the lower respiratory tract to liquify and facilitate the elimination of bronchial secretions. It also exerts a weak antiseptic effect on the pulmonary parenchyma.<ref>[http://www.sopharma.com/codterpin.phtml Codeine with Terpin hydrate] {{Webarchive|url=https://web.archive.org/web/20101120141945/http://www.sopharma.com/codterpin.phtml |date=2010-11-20 }}</ref>

==History== Terpin hydrate was first physiologically investigated by Lépine 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.<ref name=Museum>{{cite web | year = 2004 | title = Terpin Hydrate | url = http://drugstoremuseum.com/sections/level_info2.php?level_id=70 | archiveurl = https://web.archive.org/web/20110114070550/http://drugstoremuseum.com/sections/level_info2.php?level_id=70 | archivedate = 2011-01-14 | url-status = dead | publisher = Drug Store Museum }}</ref>

The following preparations of terpin hydrate were available in the United States in 1907:<ref name=Museum /> * Elixir of terpin hydrate * Elixir of terpin hydrate with codeine * Elixir of terpin hydrate with heroin

==Currently available expectorants in the United States== Currently, guaifenesin (glyceryl guaiacolate) is the only FDA approved expectorant in the United States. Besides terpin hydrate, other expectorants lacking evidence of efficacy include 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, tolu balsam and turpentine.<ref name=FDA />

==References== {{reflist}}

{{Cough and cold preparations}}

Category:Expectorants Category:Tertiary alcohols