Propylhexedrine, sold under the brand nameBenzedrex among others, is analkylamine primarily utilized as atopical nasal decongestant.[1] Its main indications are relief of congestion due tocolds,allergies, andallergic rhinitis.[2] Propylhexedrine was first used medically in 1949, with the release of Benzedrex bySmith, Kline & French, and it has been used, mainly within the United States, since then.[3]
Propylhexedrine is used to treat acutenasal congestion related to thecommon cold,allergies, andhay fever. For nasal congestion, the dosage is listed as four inhalations (two inhalations per nostril) every two hours for adults and children 6–12 years of age. Each inhalation delivers 0.4 to 0.5 mg (400 to 500μg) in 800 mL of air.[4][2][5] Use is not to exceed three days.[2]
Historically, it has also been used forweight loss inoral tablet preparations at a dose of 25 mg.[6][7] No medications containing propylhexedrine are currently approved for weight loss in any country since roughly 1976.[8]
Propylhexedrine is not recommended in individuals younger than six years of age.[10] There is at least one case of reported accidental poisoning resulting from child access to a propylhexedrine product.[11]
When used as an inhaler, the most common adverse effects warned about for propylhexedrine are temporary discomfort (e.g., stinging or burning sensations) orrebound congestion.[2] The sharing of propylhexedrine inhalers may spread infection.[2] The occurrence of these adverse effects is uncommon as propylhexedrine isgenerally recognized as safe and effective.[12] However, the use of propylhexedrine products in manners not intended by their labeling can result in severe adverse effects not typically encountered in therapeutic settings.[13][14][15] The outcomes of improperly using propylhexedrine products can include hospitalization, disability, or even death.[12] Public health agencies such as theFood and Drug Administration (FDA) have advised propylhexedrine products only be used in the manners directed on their label.[12]
Reports ofoverdoses from propylhexedrine have been documented, but they are uncommon.[16] Most instances of overdoses attributed to propylhexedrine have been the result of improper use of a propylhexedrine product in a manner not intended by its labeling for (non-medical)recreational purposes.[13] As noted by the FDA, the most common symptoms of propylhexedrine overdose are the following: "[r]apid heart rate,agitation,high blood pressure,chest pain,tremor,hallucinations,delusions,confusion,nausea, andvomiting."[13] The use of propylhexedrine products in manners inconsistent with their labeling has proven fatal in some cases.[17][18] Propylhexedrine products are considered to be safe and effective if used as intended.[13] Regardless, medical attention should be sought in the case of suspected overdose.[19]
Most of propylhexedrine's interactions with other medications have to do with its ability to constrict blood vessels. Propylhexedrine’s most serious interaction is withmonoamine oxidase inhibitors (MAOIs), which are contraindicated.[2] Monoamine oxidase inhibitors are used, albeit uncommonly, as anantidepressant.[20] Nonetheless, caution should be exercised when administering propylhexedrine concurrently with other medicines.
Propylhexedrine undergoes metabolism via N-demethylation, C-oxidation, N-oxidation, dehydrogenation, and hydrolysis to form various metabolites such asnorpropylhexedrine, cyclohexylacetoxime,cyclohexylacetone, and 4-hydroxypropylhexedrine.[28]
Hydrochloride salt of propylhexedrine. The off-brown color gives rise to the slang term for this salt: "peanut butter".[29]
Freebase propylhexedrine is a volatile, oily liquid at room temperature. The slowevaporation of freebase propylhexedrine allows it to be administered via inhalation.[30] The evaporation of the freebase also accounts for the limited shelf-life of propylhexedrine inhalers. Many of thesalts of propylhexedrine are stable, clear to off-white crystalline substances that readily dissolve in water.[31]
Propylhexedrine is achiral compound. The active ingredient contained in Benzedrex inhalers isracemic (RS)-propylhexedrine as the free base.[4] (S)-Propylhexedrine, also known as levopropylhexedrine, is the more biologically active isomer of the two.[27] Thedextrorotatory counterpart, which is mainly unused, is dextropropylhexedrine.
The selective synthesis of enantiopure levopropylhexedrine can be accomplished through the initialWenker synthesis of an intermediateaziridine followed by catalytic hydrogenation.[34]
Administration of propylhexedrine can lead to false positives forphenethylamine derivatives on urinalysis panels.[35] Propylhexedrine can be differentiated upon further analysis.[36]
Propylhexedrine's medical use as a decongestant evolved from desires to find safer alternatives to previous agents.[3] After searching for such an agent, Dr. Glenn E. Ullyot patented propylhexedrine as a decongestant in 1948. This patent was issued for benefit ofSmith, Kline & French.[37] Before it was sold nationally in the United States, propylhexedrine underwent market trials in California. These market trials began on July 15, 1949.[38] Propylhexedrine (under the brand name Benzedrex) was first introduced into commerce on August 4, 1949.[39]
Approval for use in theUnited Kingdom soon followed in 1956.[16] Later, approval for use in Canada was granted in 1998.[40] In 2023, B. F. Ascher & Co. decreased the amount of propylhexedrine in the Benzedrex inhaler from its historic 250 milligrams down to 175 milligrams.[41]
Barbexaclone, an anticonvulsant containing propylhexedrine, was used inTurkey until its withdrawal from the market in 2009. Barbexaclone's former niche in Turkish medicine is now largely occupied by [[Levetiracetam]|levetiracetam].[42]
The manufacture of propylhexedrine products for therapeutic use is typically performed based on guidelines established in government regulations and pharmacopeia monographs.[43][5]
The illicit manufacture or diversion of propylhexedrine byclandestine chemists for use as a recreational drug has been documented in academic literature.[36] Similar to when opioids are manufactured clandestinely for recreational use, it is unlikely that propylhexedrine produced by clandestine chemists adheres to the standards for purity, identity, and strength required of therapeutic products.[44]
Propylhexedrine was long reported to be a Schedule V substance inCanada.[48] In 2022, this status changed and propylhexedrine has since been removed from control under theControlled Drugs and Substances Act.[49]
Propylhexedrine is regulated as a prescription medicine inGermany.[50] Initially, propylhexedrine products (namely Obesin) were available over-the-counter. However, this changed in the 1970s and propylhexedrine is now regulated as a prescription product in Germany.[8]
Propylhexedrine was formerly aClass C substance in the United Kingdom, but was deregulated in 1995.[51] Propylhexedrine was used recreationally during a brief period in the 1970s after increased government regulation on earlier decongestants due to misuse.[52]
On the 4th of April 1988, propylhexedrine was designated a controlled substance (Schedule V) in theUnited States.[53] This was done to satisfy U.S. compliance with an international treaty. However, in 1991, this action was reversed and propylhexedrine was removed from control under the Controlled Substances Act. This was based on the opinion of theDrug Enforcement Administration that propylhexedrine did not warrant control.[54] The substance has remained unregulated under the Controlled Substances Act in the United States ever since. Furthermore, pursuant toDEA regulations, certain Benzedrex inhalers are specifically exempt from the Controlled Substances Act.[55][56] Propylhexedrine remains regulated under the laws of several U.S. states. These states include the states of Alaska,[57] Arizona,[58] Florida,[59] Georgia,[60] Idaho,[61] Kansas,[62] and Rhode Island.[63]
Multiple public health agencies (most notably within the United States) have warned against the recreational use of propylhexedrine and advised for its use only as directed by a product's labeling; nonetheless it has been reported, through the literature as early as 1959, that propylhexedrine products have been used for recreational purposes.[6] Recreational use is potentially fatal, its risks are magnified when administering the substance through injection means, and the adverse effects of recreational propylhexedrine are more severe when compared to related substances.[64][65] The undesirable side effects of propylhexedrine at recreational doses are less tolerable compared to other substances that produce similar effects; consequently, propylhexedrine is less desirable for recreational use.[19][66][17] The fact that propylhexedrine is less potent than comparable substances has also limited recreational use.[67][68] Even in areas with prevalent substance use, the use of propylhexedrine was reported as non-significant;[16] nonetheless, the recreational use of nasal decongestant,[66][69] anorectic,[6] and anticonvulsant preparations[70] of propylhexedrine has been reported. The recreational use of propylhexedrine products has been on the rise since the early 2000s.[23]
...[T]he abuse and misuse of the over-the-counter (OTC) nasal decongestant propylhexedrine can lead to serious harm such as heart and mental health problems. Some of these complications, which include fast or abnormal heart rhythm, high blood pressure, and paranoia, can lead to hospitalization, disability, or death....Propylhexedrine is safe and effective when used as directed.
Only use propylhexedrine according to the instructions on the package label. Do not use it in ways other than inhalation. Seek medical attention immediately[...] by calling [emergency services] orPoison Control[...] for anyone using propylhexedrine who experiences [any of the following:] [s]evere anxiety or agitation, confusion, hallucinations, or paranoia[,] [r]apid heartbeat or abnormal heart rhythm[,] [or] [c]hest pain or tightness[.]
A year later, in 2022, theU.S. Army published the following guidance[15] on propylhexedrine. The guidance states that recreational use of propylhexedrine is not permissible by service-members, can open its participants up to disciplinary action, and carries potentially fatal risks:
When disciplining a member for suspected use of any drug, it is important to consult [legal counsel] on how to proceed, [according to the Office of Drug Demand Reduction][...] This is especially important when the evidence supporting discipline consists of scientific reports and data that may require special assistance in their interpretation. In cases involving [propylhexedrine], legal consultation is highly recommended.
Put briefly, the FDA, Indian Health Service, and U.S.Army all advise individuals not to use propylhexedrine products for recreational purposes.
Propylhexedrine, under the brand name Benzedrex, is sold online by retailers such asAmazon,eBay, andWalmart.[4] Propylhexedrine has been sold in some countries as ananorectic or as part of ananticonvulsant preparation; however, such products are not sold freely to consumers and require a physician's prescription.
Propylhexedrine, as a nasal decongestant, is currently marketed under the trade name Benzedrex. The name Benzedrex was initially trademarked bySmith, Kline & French in 1944.[71] The brand was passed onto Menley James Laboratories (through a subsidiary, NuMark Laboratories) in 1990, and was finally acquired by B. F. Ascher & Co. in 1998.[72][73]
Propylhexedrine was also sold in inhaler form byWhitehall Laboratories (Wyeth) under theDristan brand name as an inhaler.[74] In January 1966, propylhexedrine replacedmephentermine as the active ingredient in the product.[75] The Dristan inhaler has since been discontinued. Furthermore, Wyeth was acquired byPfizer in 2009. All products currently sold under theDristan brand are manufactured by Foundation Consumer Brands; Foundation Consumer Brands acquired the Dristan brand in 2020.[76] Foundation Consumer Brands is itself owned byKelso & Company.
Propylhexedrine has also seen use inEurope as anappetite suppressant, under the trade name Obesin.[38] Obesin has been referenced in literature dating back to the 1950s.[11][6] Obesin was manufactured by Fahlberg-List inEast Germany from 1958 to around 1976. The discontinuation of Obesin was the result of increased regulatory restrictions onover-the-counteranorectics. These restrictions began to be imposed in 1974.[8] Fahlberg-List itself dissolved in 1995.
Propylhexedrine (in the form of levopropylhexedrine) is a component in theanticonvulsant preparationbarbexaclone. It is included for the purpose of offsetting thebarbiturate-inducedsedation fromphenobarbital.[38] Barbexaclone has been known under the brand name of Maliasin, manufactured byAbbott Laboratories, as early as 1965.[77][78] Maliasin has also been manufactured byKnoll Pharmaceuticals; Knoll is a company acquired byAbbott Laboratories. In 2010, Abbott discontinued sale of its barbexaclone preparation in many countries.[79]
^abcdRose W (September 1959). "Arzneimittelsucht durch Mißbrauch von sogenannten Appetitzüglern (Obesin)" [Drug addiction due to abuse of so-called appetite suppressants (Obesin)].Archiv für Toxikologie (in German).17 (5):331–335.Bibcode:1959ArTox..17..331R.doi:10.1007/BF00577633.ISSN1432-0738.S2CID31539217.
^"Propylhexedrine".www.mskcc.org. Memorial Sloan Kettering Cancer Center. Archived fromthe original on 9 August 2023. Retrieved16 July 2023.
^abPolster H (February 1965). "Über eine Vergiftung mit dem Appetitzügler Propylhexedrin "Obesin", bei einem 3 Ährigen Kinde" [About poisoning with the appetite suppressant propylhexedrine "Obesin" in a 3-year-old child].Archiv für Toxikologie (in German).20 (5):271–273.doi:10.1007/BF00577551.PMID14272412.S2CID19812917.
^abcSmith DE, Wesson DR, Sees KL, Morgan JP (1 October 1988). "An epidemiological and clinical analysis of propylhexedrine abuse in the United States".Journal of Psychoactive Drugs.20 (4):441–442.doi:10.1080/02791072.1988.10472514.PMID2907528.
^Schmidt JL, Fleming WW (July 1964). "A Nonsympathomimetic Effect of Cyclopentamine and Beta-Mercaptoethylamine in the Rabbit Ileum".The Journal of Pharmacology and Experimental Therapeutics.145:83–86.doi:10.1016/S0022-3565(25)26827-6.PMID14209515.
^Delicado EG, Fideu MD, Miras-Portugal MT, Pourrias B, Aunis D (August 1990). "Effect of tuamine, heptaminol and two analogues on uptake and release of catecholamines in cultured chromaffin cells".Biochemical Pharmacology.40 (4):821–825.doi:10.1016/0006-2952(90)90322-c.PMID2386550.
^abMidha KK, Beckett AH, Saunders A (October 1974). "Identification of the major metabolites of propylhexedrine in vivo (in man) and in vitro (in guinea pig and rabbit)".Xenobiotica; the Fate of Foreign Compounds in Biological Systems.4 (10):627–635.doi:10.1080/00498257409169765.PMID4428789.
^Schaiberger PH, Kennedy TC, Miller FC, Gal J, Petty TL (August 1993). "Pulmonary hypertension associated with long-term inhalation of "crank" methamphetamine".Chest.104 (2):614–616.doi:10.1378/chest.104.2.614.PMID8101799.
^US granted 4095596, Grayson M, "Nasal Inhaler", issued 20 June 1978, assigned to Smithkline Corp.
^Mancusi-Ungaro HR, Decker WJ, Forshan VR, Blackwell SJ, Lewis SR (1983). "Tissue injuries associated with parenteral propylhexedrine abuse".Journal of Toxicology. Clinical Toxicology.21 (3):359–372.doi:10.1097/00005373-198307000-00114.PMID6144800.
^Lednicer D, Mitscher LA (1977).Organic Chemistry of Drug Synthesis. Vol. 1. New York, NY: Wiley. p. 37.ISBN978-0-471-52141-9.
^Thurman EM, Pedersen MJ, Stout RL, Martin T (1992). "Distinguishing sympathomimetic amines from amphetamine and methamphetamine in urine by gas chromatography/mass spectrometry".Journal of Analytical Toxicology.16 (1):19–27.doi:10.1093/jat/16.1.19.PMID1640694.
^"Propylhexedrine - NAPRA".(Canadian) National Association of Pharmacy Regulatory Authorities. Archived fromthe original on 15 July 2023. Retrieved15 July 2023.
^Bolukbasi F, Delil S, Bulus E, Senturk A, Yeni N, Karaagac N (September 2013). "End of the barbexaclone era: an experience of treatment withdrawal".Epileptic Disorders.15 (3):311–313.doi:10.1684/epd.2013.0605.PMID23981808.S2CID39112148.
^Angrist BM, Schweitzer JW, Gershon S, Friedhoff AJ (March 1970). "Mephentermine psychosis: misuse of the Wyamine inhaler".The American Journal of Psychiatry.126 (9):1315–1317.doi:10.1176/ajp.126.9.1315.PMID5413209.
^Krueger HJ, Schwarz H (April 1965). "[Clinical Communication on the Therapy of Epilepsy With Maliasin]".Die Medizinische Welt.14:690–692.PMID14276849.
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