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Systematic (IUPAC) name
Clinical data
  • C
Legal status
Routes of
Pharmacokinetic data
Bioavailability 89-98% orally
Metabolism sympathetic nervous system
Biological half-life 36-48 hours
Excretion feces and urine
CAS Registry Number  Y
ATC code R03 R03 QG02
PubChem CID:
DrugBank  Y
ChemSpider  Y
Chemical data
Formula C12H18Cl2N2O
Molecular mass 277.19

Clenbuterol, marketed as Dilaterol, Spiropent, Ventipulmin, and also generically as clenbuterol, is a sympathomimetic amine used by sufferers of breathing disorders as a decongestant and bronchodilator. People with chronic breathing disorders such as asthma use this as a bronchodilator to make breathing easier. It is most commonly available as the hydrochloride salt, clenbuterol hydrochloride.


  • Effects and dosage 1
  • Human use 2
    • Legal status 2.1
    • Weight-loss drug 2.2
    • Notable cases of use as performance-enhancing drug 2.3
    • Side effects and dangers 2.4
    • Overdosage 2.5
    • Food contamination 2.6
  • Veterinary use 3
  • See also 4
  • References 5
  • External links 6

Effects and dosage

Clenbuterol is a β2 agonist with some structural and pharmacological similarities to epinephrine and salbutamol, but its effects are more potent and longer-lasting as a stimulant and thermogenic drug. It causes an increase in aerobic capacity, central nervous system stimulation, blood pressure, and oxygen transportation. It increases the rate at which body fat is metabolized while increasing the body's basal metabolic rate (BMR). It is commonly used for smooth muscle-relaxant properties as a bronchodilator and tocolytic.

Clenbuterol is also prescribed for treatment of horses, but equine use is usually the liquid form.

Human use

Clenbuterol is approved for use in some countries, free or via prescription, as a bronchodilator for asthma patients.[1]

Legal status

Clenbuterol is not an ingredient of any therapeutic drug approved by the US Food and Drug Administration[1] and is now banned for IOC-tested athletes.[2] In the US, administration of clenbuterol to any animal that could be used as food for human consumption is banned by the FDA.[3]

Clenbuterol is a therapeutic drug for asthma, approved for human use in some countries in Europe (Bulgaria and Russia) and Asia (China).

Weight-loss drug

Although often used by bodybuilders during their "cutting" cycles, the drug has been more recently known to the mainstream, particularly through publicized stories of use by celebrities such as Victoria Beckham,[2] Britney Spears, and Lindsay Lohan, [4] for its off-label use as a weight-loss drug similar to usage of other sympathomimetic amines such as ephedrine, despite the lack of sufficient clinical testing either supporting or negating such use.

Notable cases of use as performance-enhancing drug

As a β2 sympathomimetic, clenbuterol has also been used as a performance-enhancing drug.

A three-year suspension for taking clenbuterol kept sprinter Katrin Krabbe from competing in the 1992 Summer Olympics, and effectively ended her athletic career.[5][6][7]

In 2006, San Francisco Giants pitcher Guillermo Mota, while a member of the New York Mets, received a 50-game suspension after testing positive for clenbuterol.[8] In 2012, MLB officials announced they were again suspending Mota for 100 games due a positive test for clenbuterol.[9]

American swimmer Jessica Hardy tested positive at the US trials in 2008. She was subject to a one-year suspension, having claimed she unknowingly took the drug in a contaminated food supplement. Former New York Mets clubhouse employee Kirk Radomski admitted in his plea deal to distributing clenbuterol to dozens of current and former Major League Baseball players and associates.[10] After finishing fourth in the K-2 1000-m event at the 2008 Summer Olympics in Beijing, Polish sprint canoer Adam Seroczyński was disqualified for taking this drug, and Chinese cyclist Li Fuyu tested positive for it at the Dwars door Vlaanderen race in Belgium on March 24, 2010.[11]

In 2010, St. Louis Cardinals minor-league shortstop Lainer Bueno received a 50-game suspension for the 2011 season as a result of testing positive for clenbuterol.[12] Cyclist Alberto Contador of Spain was banned for two years from professional cycling after testing positive for the drug at the 2010 Tour de France.[13] He was later stripped of the 2010 title of the Tour de France and the 2011 title of the Giro d'Italia.[14] CAS found that Contador probably tested positive due to a contaminated food supplement.[15] In 2013, Contador's team-mate on the Team Saxo Bank squad, Mick Rogers, tested positive for clenbuterol at the Japan Cup bike race. In April 2014 the Union Cycliste Internationale announced that it accepted Rogers' explanation that the substance had been ingested by him after consuming contaminated meat whilst competing at the 2013 Tour of Beijing, upholding Rogers' disqualification from the Japan Cup but declining to impose any further sanctions on him.[16]

In 2011, players of the Mexico national football team were found with clenbuterol in their bloodstreams, but were acquitted by WADA after they claimed the clenbuterol came from contaminated food. FIFA has also claimed 109 players from the Under-17 World Cup in Mexico tested positive for this drug, because Mexican meat is contaminated.[17]

In 2013, Mexican boxer Erik Morales was suspended for two years after testing positive for clenbuterol.[18]

In 2014, Toronto Maple Leafs Forward Carter Ashton was suspended from the NHL for 20 games without pay for violating the NHL/NHL Players' Association Performance Enhancing Substances Program after it was determined that he had ingested Clenbuterol. Carter claimed he used an unprescribed asthma inhaler.[19]

In 2014, South Korean swimmer Kim Ji-heun has tested positive for the banned substance Clenbuterol at an out-of-competition test on May 13, 2014. After completion of proceedings by the Korea Anti-Doping Disciplinary Panel, Kim received a two-year suspension, back-dated to the day of his positive test.[20]

In 2014, Czech body builder Petr Soukup received a lifetime ban after a positive test for clenbuterol, metenolon, mesterolon, methamphetamin, oxandrolon, stanozolol, nandrolon, fluoxymesterone, DHCMtestosteron and metandienon.[21]

In 2015, Yankees minor league pitching prospect Moises Cedeno tested positive for the banned substance Clenbuterol and was suspended for 72 games.[22]

In 2015, two players from the Collingwood Football Club in Australia were delisted from the club and accepted 2-year bans from all sport in Australia after testing positive to the substance, which they believe may have been in a contaminated illicit drug they consumed.[23][24]

Side effects and dangers

Clenbuterol can cause these side effects:


Excessive use over the recommended dose of about 120 μg can cause muscle tremors, headache, dizziness, and gastric irritation. Persons self-administering the drug for weight loss or to improve athletic performance have experienced nausea, vomiting, diaphoresis, palpitations, tachycardia, and myocardial infarction. Use of the drug may be confirmed by detecting its presence in semen or urine.[25]

Food contamination

Clenbuterol is occasionally referred to as "bute" and this risks confusion with phenylbutazone, also called "bute". Phenylbutazone, which is a drug also used with horses, was tested for in the 2013 European meat adulteration scandal.[26]

Intended to result in leaner meat with a higher muscle-to-fat ratio, the use of clenbuterol has been banned in meat since 1991 in the USA and since 1996 in the European Union. The drug is banned due to health concerns about symptoms noted in consumers. These include increased heart rate, muscular tremors, headaches, nausea, fever, and chills. In several cases in Europe, these adverse symptoms have been temporary.[27]

Clenbuterol is a growth-promoting drug in the β-agonist class of compounds. It is not licensed for use in China[28] or the United States[27] or the EU[29] for food producing animals, but some countries have approved it for animals not used for food, and a few countries have approved it for therapeutic uses in food-producing animals.

Not just athletes are affected by contamination. In Portugal, 50 people were reported as affected by clenbuterol in liver and pork between 1998 and 2002, while in 1990, veal liver was suspected of causing clenbuterol poisoning in 22 people in France and 135 people in Spain.[30]

In September 2006, over 330 people in Shanghai were reported to have food poisoning by eating clenbuterol-contaminated pork that had been fed to the animals to keep the meat lean.[31]

In February 2009, at least 70 people in one

  • Charles F. Kearns, Kenneth H. McKeever, Karyn Malinowski, Maggie B. Struck, and Takashi Abe (2001). "Chronic administration of therapeutic levels of clenbuterol acts as a repartitioning agent". J Appl Physiol 91 (5): 2064–2070.  

External links

  1. ^ a b "Clenbuterol". Daily Mail. 2009-10-01. Retrieved 2010-04-07 
  2. ^ a b Guest, Katy (2007-04-10). "Clenbuterol: The new weight-loss wonder drug gripping Planet Zero". The Independent (London). Retrieved 2007-04-10. 
  3. ^ FDA's Prohibited Drug List, Food Animal Residue Avoidance & Depletion Program
  4. ^ "Clenbuterol Weight Loss Hollywood Secret". PRBuzz (London). 2012-05-17. Retrieved 2012-04-10. 
  5. ^ [3]
  6. ^ "Krabbe receives IAAF settlement". BBC News. 2002-04-30. 
  7. ^ [4]
  8. ^
  9. ^ Dittmeier, Bobbie (May 7, 2012). "Mota suspended 100 games for positive test".  
  10. ^ Snyder, Whitney (2010-09-30). "Alberto Contador Tests Positive For Banned Substance". Huffington Post. 
  11. ^ Radioshack suspends Li after doping positive
  12. ^ "Three Minor League players suspended". September 30, 2010. 
  13. ^ Macur, Juliet (29 September 2010). "With Positive Test, Contador May Lose Tour Title". The New York Times. Retrieved 29 September 2010. 
  14. ^ CAS Sanction Contador with two year ban in clenbuterol case,, 6 February 2012
  15. ^
  16. ^ "Michael Rogers cleared to race as UCI accepts contaminated meat claim".  
  17. ^ "FIFA alarmed by use of food supplements". September 5, 2012. 
  18. ^
  19. ^
  20. ^ swim
  21. ^
  22. ^
  23. ^
  24. ^
  25. ^ R. Baselt, Disposition of Toxic Drugs and Chemicals in Man, 8th edition, Biomedical Publications, Foster City, CA, 2008, pp. 325–326.
  26. ^ "Horse meat investigation. Advice for consumers". Enforcement and regulation.  
  27. ^ a b "Clenbuterol", Food Safety and Inspection Service (FSIS), July 1995, Retrieved 8 April 2015
  28. ^ China bans production, sale of clenbuterol to improve food safety Retrieved 08/22/2012
  29. ^ European Commission Retrieved 08/22/2012
  30. ^ Anti Doping Advisory Notes Retrieved 08/22/2012
  31. ^ "Pigs fed on bodybuilder steroids cause food poisoning in Shanghai". AFP. 2006-09-19. Retrieved 2006-09-19. 
  32. ^ "China: 70 ill from tainted pig organs". CNN. 2009-02-23. Retrieved 2010-04-30. 
  33. ^ Wang Ying (2009-02-23). "70 ill after eating tainted pig organs". China Daily. 
  34. ^ "China to launch one-year crackdown on contaminated pig feed –". Xinhua. 2011-03-28. Retrieved 2011-03-29. 
  35. ^ Food Safety News Retrieved 08/22/2012
  36. ^ Planipart Solution for Injection 30 micrograms/ml: Uses, National Office of Animal Health


  • Mabuterol (same structure as clenbuterol but one of the chloro groups has been changed to a trifluoromethyl group instead).
  • Cimaterol

See also

The US and the EU prohibit the use of clenbuterol in food-producing animals. It is, however, used in other parts of the world for the treatment of allergic respiratory disease in horses, as it is a bronchodilator. A common trade name is Ventipulmin. It can be used both orally and intravenously. It is also used in cattle to relax the uterus in cows, usually at the time of parturition.[36] It is also a nonsteroidal anabolic and metabolism accelerator, through a mechanism not well understood.

Veterinary use

Authorities around the world appear to be issuing stricter food safety requirements, such as the Food Safety Modernization Act in the United States, Canada’s revision of their import regulations, China’s new food laws published since 2009, South Africa's new food law, and many more global changes and restrictions.

In March 2011, China's Ministry of Agriculture said the government would launch a one-year crackdown on illegal additives in pig feed, after a subsidiary of Shuanghui Group, China's largest meat producer, was exposed for using clenbuterol-contaminated pork in its meat products. A total of 72 people in central Henan Province, where Shuanghui is based, were taken into police custody for allegedly producing, selling or using clenbuterol.[34] The situation has dramatically improved in China since September 2011, when a ban of clenbuterol was announced by China’s Ministry of Agriculture.[35]


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