Clinical data | |||
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Trade names | Benzedrex, Obesin, Dristan Inhaler, and others | ||
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AHFS/Drugs.com | Monograph | ||
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Routes of administration | Medical: Intranasal (inhaler) Recreational: Oral, parenteral | ||
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Pharmacokinetic data | |||
Elimination half-life | 4 ± 1.5 hours | ||
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CompTox Dashboard (EPA) | |||
ECHA InfoCard | 100.002.673 | ||
Chemical and physical data | |||
Formula | C10H21N | ||
Molar mass | 155.285 g·mol−1 | ||
3D model (JSmol) | |||
Chirality | Racemic mixture | ||
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Propylhexedrine, sold under the brand name Benzedrex among others, is an alkylamine primarily utilized as a topical nasal decongestant. [1] Its main indications are relief of congestion due to colds, allergies, and allergic rhinitis. [2] Propylhexedrine was first used medically in 1949, with the release of Benzedrex by Smith, Kline & French, and it has been used, mainly within the United States, since then. [3]
Propylhexedrine is used to treat acute nasal congestion related to the common cold, allergies, and hay 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 500 μg) in 800 mL of air. [4] [2] [5] Use is not to exceed three days. [2]
Historically, it has also been used for weight loss in oral 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 should not be used if a MAOI has been used in the past 14 days or is currently in use by a person. [2]
Unlike other topical decongestants, propylhexedrine is not required to carry a warning against use in individuals with hypertension. [9]
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) or rebound congestion. [2] The sharing of propylhexedrine inhalers may spread infection. [2] The occurrence of these adverse effects is uncommon as propylhexedrine is generally 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 the Food and Drug Administration (FDA) have advised propylhexedrine products only be used in the manners directed on their label. [12]
Reports of overdoses 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, and vomiting." [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 with monoamine oxidase inhibitors (MAOIs), which are contraindicated. [2] Monoamine oxidase inhibitors are used, albeit uncommonly, as an antidepressant. [20] Nonetheless, caution should be exercised when administering propylhexedrine concurrently with other medicines.
Propylhexedrine works mainly as an adrenergic agonist, when used at therapeutic doses in an inhaler dosage form. [21] This restricts the blood vessels in the nose and reduces swelling; thereby, it relieves nasal congestion. [22] At higher doses, propylhexedrine affects the central nervous system as a norepinephrine–dopamine releasing agent (NDRA). [23] Propylhexedrine likely exerts such effects in a manner similar to related alkylamines such as cyclopentamine, methylhexanamine, and tuaminoheptane. [24] [25] [26] In addition, propylhexedrine further releases monoamines through TAAR1 agonism and VMAT2 inhibition. [21] Propylhexedrine also exhibits antihypotensive effects. [27]
Propylhexedrine undergoes metabolism via N-demethylation, C-oxidation, N-oxidation, dehydrogenation, and hydrolysis to form various metabolites such as norpropylhexedrine, cyclohexylacetoxime, cyclohexylacetone, and 4-hydroxypropylhexedrine. [28]
Freebase propylhexedrine is a volatile, oily liquid at room temperature. The slow evaporation 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 the salts of propylhexedrine are stable, clear to off-white crystalline substances that readily dissolve in water. [31]
Propylhexedrine is similar in chemical structure to phenylethylamines. Phenylethylamines and substituted phenethylamines are found in the core of many trace amines and sympathomimetic drugs. The main difference is the presence of an alicyclic cyclohexyl group instead of the aromatic phenyl group of a phenethylamine.
Propylhexedrine is a chiral compound. The active ingredient contained in Benzedrex inhalers is racemic (RS)-propylhexedrine as the free base. [4] (S)-Propylhexedrine, also known as levopropylhexedrine, is believed to be the more biologically active isomer of the two. [27] The dextrorotatory counterpart, which is mainly unused, is dextropropylhexedrine.
Propylhexedrine can be synthesized from cyclohexylacetone through the reductive amination of an intermediary imine over an aluminum-mercury amalgam in the presence of a hydrogen source. [32]
However, propylhexedrine is more commonly prepared by the catalytic hydrogenation of methamphetamine over Adams' catalyst. This transforms methamphetamine's phenyl ring to a cyclohexyl moiety. [33]
Due to its structure, administration of propylhexedrine can lead to false positives for phenethylamine derivatives on urinalysis panels. [34] Propylhexedrine can be differentiated upon further analysis. [35]
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 of Smith, Kline & French. [36] Before it was sold nationally in the United States, propylhexedrine underwent market trials in California. These market trials began on July 15, 1949. [37] Propylhexedrine (under the brand name Benzedrex) was first introduced into interstate commerce on August 4, 1949. [38]
Approval for use in the United Kingdom soon followed in 1956. [16] Later, approval for use in Canada was granted in 1998. [39] In 2023, B. F. Ascher & Co. decreased the amount of propylhexedrine in the Benzedrex inhaler from its historic 250 milligrams down to 175 milligrams. [40]
Barbexaclone, an anticonvulsant containing propylhexedrine, was used in Turkey until its withdrawal from the market in 2009. Barbexaclone's former niche in Turkish medicine is now largely occupied by levetiracetam. [41]
The manufacture of propylhexedrine products for therapeutic use is typically performed based on guidelines established in government regulations and pharmacopeia monographs. [42] [5]
The illicit manufacture or diversion of propylhexedrine by clandestine chemists for use as a recreational drug has been documented in academic literature. [35] 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. [43]
Propylhexedrine was placed under international control by the Convention on Psychotropic Substances in 1985. This action was reversed in 1991. [44]
Propylhexedrine was long reported to be a Schedule V substance in Canada. [47] In 2022, this status changed and propylhexedrine has since been removed from control under the Controlled Drugs and Substances Act. [48]
Propylhexedrine is regulated as a prescription medicine in Germany. [49] 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]
It was formerly a Class C substance in the United Kingdom, but was deregulated in 1995. [50] Propylhexedrine was used recreationally during a brief period in the 1970s after increased government regulation on earlier decongestants due to misuse. [51]
On the 4th of April 1988, propylhexedrine was designated a controlled substance (Schedule V) in the United States. [52] 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 the Drug Enforcement Administration that propylhexedrine did not warrant control. [53] The substance has remained unregulated under the Controlled Substances Act in the United States ever since. Furthermore, pursuant to DEA regulations, certain Benzedrex inhalers are specifically exempt from the Controlled Substances Act. [54] [55] Propylhexedrine remains regulated under the laws of several U.S. states. These states include the states of Alaska, [56] Arizona, [57] Florida, [58] Georgia, [59] Idaho, [60] Kansas, [61] and Rhode Island. [62]
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. [63] [64] 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] [65] [17] The fact that propylhexedrine is less potent than comparable substances has also limited recreational use. [66] [67] Even in areas with prevalent substance use, the use of propylhexedrine was reported as non-significant. [16] The recreational use of nasal decongestant, [65] [68] anorectic, [6] and anticonvulsant preparations [69] have all been reported. The recreational use of propylhexedrine products has been on the rise since the early 2000s. [23]
In 2021, the Food and Drug Administration (FDA) issued the following warning [13] in regard to recreational use of propylhexedrine products in manners inconsistent with their labeling:
"...[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."
That same year, the Indian Health Service issued the following statement [14] in reference to the recreational use of propylhexedrine products:
Only use propylhexedrine according to the instructions on the package label. Do not use it in ways other than inhalation. Seek medical attention immediately for by calling [emergency services] or Poison Control...for anyone using propylhexedrine who experiences [the following.] [These following reactions are] [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, the U.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 as Amazon, eBay, and Walmart. [4] Propylhexedrine has been sold in some countries as an anorectic or as part of an anticonvulsant 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 by Smith, Kline & French in 1944. [70] 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. [71] [72]
Propylhexedrine was also sold in inhaler form by Whitehall Laboratories (Wyeth) under the Dristan brand name as an inhaler. [73] In January 1966, propylhexedrine replaced mephentermine as the active ingredient in the product. [74] The Dristan inhaler has since been discontinued. Furthermore, Wyeth was acquired by Pfizer in 2009. All products currently sold under the Dristan brand are manufactured by Foundation Consumer Brands; Foundation Consumer Brands acquired the Dristan brand in 2020. [75] Foundation Consumer Brands is itself owned by Kelso & Company.
Propylhexedrine has also seen use in Europe as an appetite suppressant, under the trade name Obesin. [37] Obesin has been referenced in literature dating back to the 1950s. [11] [6] Obesin was manufactured by Fahlberg-List in East Germany from 1958 to around 1976. The discontinuation of Obesin was the result of increased regulatory restrictions on over-the-counter anorectics. These restrictions began to be imposed in 1974. [8] Fahlberg-List itself dissolved in 1995.
Propylhexedrine is a component in the anticonvulsant preparation barbexaclone. Its S-isomer (levopropylhexedrine or L-propylhexedrine) is bonded with phenobarbital for the purpose of offsetting the barbiturate-induced sedation. [37] Barbexaclone has been known under the brand name of Maliasin, manufactured by Abbott Laboratories, as early as 1965. [76] [77] Maliasin has also been manufactured by Knoll Pharmaceuticals; Knoll is a company acquired by Abbott Laboratories. In 2010, Abbott discontinued sale of its barbexaclone preparation in many countries. [78]
Levopropylhexedrine (the more active optical isomer of propylhexedrine) has been used as an appetite suppressant under the brand name Eventin. Eventin's use has been documented as early as 1958. [79]
Oxycodone, sold under the brand name Roxicodone and OxyContin among others, is a semi-synthetic opioid used medically for treatment of moderate to severe pain. It is highly addictive and is a commonly abused drug. It is usually taken by mouth, and is available in immediate-release and controlled-release formulations. Onset of pain relief typically begins within fifteen minutes and lasts for up to six hours with the immediate-release formulation. In the United Kingdom, it is available by injection. Combination products are also available with paracetamol (acetaminophen), ibuprofen, naloxone, naltrexone, and aspirin.
Pseudoephedrine, sold under the brand name Sudafed among others, is a sympathomimetic medication which is used as a decongestant to treat nasal congestion. It has also been used off-label for certain other indications, like treatment of low blood pressure. At higher doses, it may produce various additional effects including stimulant, appetite suppressant, and performance-enhancing effects. In relation to this, non-medical use of pseudoephedrine has been encountered. The medication is taken by mouth.
Cold medicines are a group of medications taken individually or in combination as a treatment for the symptoms of the common cold and similar conditions of the upper respiratory tract. The term encompasses a broad array of drugs, including analgesics, antihistamines and decongestants, among many others. It also includes drugs which are marketed as cough suppressants or antitussives, but their effectiveness in reducing cough symptoms is unclear or minimal.
A prescription drug is a pharmaceutical drug that is permitted to be dispensed only to those with a medical prescription. In contrast, over-the-counter drugs can be obtained without a prescription. The reason for this difference in substance control is the potential scope of misuse, from drug abuse to practicing medicine without a license and without sufficient education. Different jurisdictions have different definitions of what constitutes a prescription drug.
A decongestant, or nasal decongestant, is a type of pharmaceutical drug that is used to relieve nasal congestion in the upper respiratory tract. The active ingredient in most decongestants is either pseudoephedrine or phenylephrine. Intranasal corticosteroids can also be used as decongestants and antihistamines can be used to alleviate runny nose, nasal itch, and sneezing.
Oxymorphone is a highly potent opioid analgesic indicated for treatment of severe pain. Pain relief after injection begins after about 5–10 minutes, after oral administration it begins after about 30 minutes, and lasts about 3–4 hours for immediate-release tablets and 12 hours for extended-release tablets. The elimination half-life of oxymorphone is much faster intravenously, and as such, the drug is most commonly used orally. Like oxycodone, which metabolizes to oxymorphone, oxymorphone has a high potential to be abused.
Nicotine replacement therapy (NRT) is a medically approved way to treat people with tobacco use disorder by taking nicotine through means other than tobacco. It is used to help with quitting smoking or stopping chewing tobacco. It increases the chance of quitting tobacco smoking by about 55%. Often it is used along with other behavioral techniques. NRT has also been used to treat ulcerative colitis. Types of NRT include the adhesive patch, chewing gum, lozenges, nose spray, and inhaler. The use of multiple types of NRT at a time may increase effectiveness.
Phenylephrine, sold under the brand names Neosynephrine and Sudafed PE among others, is a medication used as a decongestant for uncomplicated nasal congestion, to dilate the pupil, to increase blood pressure, and to relieve hemorrhoids. It can be taken by mouth, as a nasal spray, given by injection into a vein or muscle, applied to the skin, or as a rectal suppository.
Pregabalin, sold under the brand name Lyrica among others, is an anticonvulsant, analgesic, and anxiolytic amino acid medication used to treat epilepsy, neuropathic pain, fibromyalgia, restless legs syndrome, opioid withdrawal, and generalized anxiety disorder (GAD). Pregabalin also has antiallodynic properties. Its use in epilepsy is as an add-on therapy for partial seizures. It is a gabapentinoid medication which are drugs that are derivatives of γ-aminobutyric acid (GABA), an inhibitory neurotransmitter. Pregabalin acts by inhibiting certain calcium channels. When used before surgery, it reduces pain but results in greater sedation and visual disturbances. It is taken by mouth.
Naphazoline is a medicine used as a decongestant, and a vasoconstrictor added to eye drops to relieve red eye. It has a rapid action in reducing swelling when applied to mucous membranes. It is a sympathomimetic agent with marked alpha adrenergic activity that acts on alpha-receptors in the arterioles of the conjunctiva to produce constriction, resulting in decreased congestion.
Actifed is a registered trademark for a combination antihistamine and nasal decongestant medication used for cold and allergy symptoms. Actifed was developed in 1958 by Burroughs Wellcome & Company, later Haleon.
Levmetamfetamine, also known as l-desoxyephedrine or levomethamphetamine, and commonly sold under the brand name Vicks VapoInhaler among others, is an optical isomer of methamphetamine primarily used as a topical nasal decongestant. It is used to treat nasal congestion from allergies and the common cold. It was first used medically as decongestant beginning in 1958 and has been used for such purposes, primarily in the United States, since then.
Sodium oxybate, sold under the brand name Xyrem among others, is a medication used to treat symptoms of narcolepsy: sudden muscle weakness and excessive daytime sleepiness. It is used sometimes in France and Italy as an anesthetic given intravenously; it is also approved and used in Italy and in Austria to treat alcohol dependence and alcohol withdrawal syndrome.
A drug is any chemical substance other than a nutrient or an essential dietary ingredient, which, when administered to a living organism, produces a biological effect. Consumption of drugs can be via inhalation, injection, smoking, ingestion, absorption via a patch on the skin, suppository, or dissolution under the tongue.
Tapentadol, sold under the brand names Nucynta and Palexia among others, is a synthetic opioid analgesic of the benzenoid class with a dual mode of action as a highly selective full agonist of the μ-opioid receptor and as a norepinephrine reuptake inhibitor (NRI). Tapentadol is used medically for the treatment of moderate to severe pain. It is addictive, a commonly abused drug, and poses a high risk of physical and/or mental dependence.
Methylhexanamine is an indirect sympathomimetic drug invented and developed by Eli Lilly and Company and marketed as an inhaled nasal decongestant from 1948 until it was voluntarily withdrawn from the market in the 1980s.
Perampanel, sold under the brand name Fycompa, is an anti-epileptic medication developed by Eisai Co. that is used in addition to other drugs to treat partial seizures and generalized tonic-clonic seizures for people older than twelve years. It was first approved in 2012, and as of 2016, its optimal role in the treatment of epilepsy relative to other drugs was not clear. It was the first antiepileptic drug in the class of selective non-competitive antagonist of AMPA receptors.
Methiopropamine (MPA), also known as N-methylthiopropamine, is an organic compound structurally related to methamphetamine. Originally reported in 1942, the molecule consists of a thiophene group with an alkyl amine substituent at the 2-position. It appeared for public sale in the United Kingdom in December 2010 as a "research chemical" or "legal high", recently branded as Blow. It has limited popularity as a recreational stimulant.
Budesonide, sold under the brand name Pulmicort, among others, is a steroid medication. It is available as an inhaler, nebulization solution, pill, nasal spray, and rectal forms. The inhaled form is used in the long-term management of asthma and chronic obstructive pulmonary disease (COPD). The nasal spray is used for allergic rhinitis and nasal polyps. Modified-release pills or capsules and rectal forms may be used for inflammatory bowel disease including Crohn's disease, ulcerative colitis, and microscopic colitis.
Methamphetamine in the United States is regulated under Schedule II of the Controlled Substances Act. It is approved for pharmacological use in the treatment of attention deficit hyperactivity disorder, narcolepsy, and treatment-resistant obesity, but it is primarily used as a recreational drug. In 2012, 16,000 prescriptions for methamphetamine were filled, approximately 1.2 million Americans reported using it in the past year, and 440,000 reported using the drug in the past month.