Clenbuterol ( Clenbuterol , “Maple” ) – a drug used in medicine to treat asthma . In recent years, clenbuterol has found widespread use in bodybuilding and fitness due to its ability to burn fat, therefore it is often used by athletes for weight loss and drying. Clenbuterol courses often include thyroxine and ketotifen to speed up the weight loss process.

Clenbuterol is not related to anabolic steroids and belongs to the group of adrenomimetics , which exert their physiological effect by stimulating beta-2-adrenergic receptors , as a result of which it is activatedthe sympathetic nervous system and lipolysis is triggered . A prescription is required to purchase the drug.

It can be prescribed to girls without the risk of developing androgenic side effects inherent in anabolic steroids .

Half-life: 36 hours

Doping status 

Clenbuterol has been banned by WADA for use in sports since 1992. Standard anti-doping tests usually respond to a urinary concentration of 5-10 ng / L, which is observed 4-5 days after the last dose. More sensitive tests increase the detection time of clenbuterol to 2-3 weeks or more (1-2 ng / l). The drug accumulates in adipose tissue and can be more actively released during exercise or competition.

One of the possible ways of getting clenbuterol into the athlete’s body may be meat, since in some countries (China, Mexico) it is used to increase the weight of fattened animals.

Several scientific articles report frequent inappropriate inclusion of clenbuterol in sports supplements for burning fat.

Mechanism of action

As a beta-2 agonist , clenbuterol acts as a fat burner by binding to type 2 beta receptors in the fat and muscle tissue of the human body. After clenbuterol binds to the receptor, a cascade of biochemical reactions is triggered that lead to an increase in the synthesis of cAMP (cyclic adenosine monophosphate). cAMP, in turn, activates enzymes that mobilize fatty acids from adipocytes (adipose tissue cells).

With the action of clenbuterol on the beta-2-adrenergic receptors of the presynaptic membrane, the release of norepinephrine and adrenaline increases, which have a powerful fat-burning effect. Clenbuterol increases the basal metabolic rate by 20-30% of the initial level.

Clenbuterol inhibits the activity of lipoprotein lipase, as a result of which the deposition of fat in adipose tissue becomes impossible. Acting on the beta-2-adrenergic receptors of the central nervous system, this drug increases the secretion of thyroid hormones – the body’s natural fat burners.

A unique feature of clenbuterol is that it is not only a powerful fat burner, but also has a pronounced anti-catabolic effect , protecting muscles from destruction, which is very important during weight loss and drying in bodybuilding. In studies, it was found that the anti-catabolic effect of the drug is due to the blocking of Ca 2+ -dependent and ubiquitin-proteasome proteolysis.

A 2012 study (Francesca Wannenes, Loretta Magni) confirms the ability of clenbuterol to block the mechanisms of muscle wasting. A new 2014 study showed that β-agonists ( catecholamines ) released during intense exercise induce CREB-mediated transcription by activating its obligate coactivators CRTC2 and Crtc3.

In contrast to catabolic activity, usually associated with the function of the sympathetic nervous system, activation of Crtc / Creb proteins in the skeletal muscles of transgenic mice leads to an increase in anabolic processes and increased protein synthesis. Thus, in animals with overexpression of CRTC2, the cross-sectional area of ​​myofibrils increases, the content of intramuscular triglycerides and the content of glycogen increase. In addition, there is a significant increase in strength indicators.

Due to the above mechanisms, the drug has a moderate anabolic effect, which has been proven in human experiments and practical use in bodybuilding.

Considering the fact that the drug practically does not interact with beta-1-adrenergic receptors, there is an expansion of the bronchi and easier breathing, as well as a much lower frequency of side effects from the cardiovascular system compared to non-selective agonists such as ephedrine .

Human studies 

The 2015 Lee P. study was the first reliable evidence of the efficacy of beta-agonists in humans. An analogue of the mechanism of action of formoterol ( β2 selective agonist ) at a dose of 160 μg / day stimulated anabolism, increased protein synthesis, without causing side effects from the cardiovascular system, while these effects are more pronounced in girls.

In addition, Morten Hostrup (2015) found that beta-2-adrenergic agonist terbutaline (10-15 mg / day) causes a statistically significant increase in lean muscle mass, increases strength and endurance with maximum exercise on an exercise bike .

Effects of clenbuterol

  • Burn fat and dry muscle
  • Increased strength and endurance
  • Temperature increase
  • Decreased appetite
  • Psychic activation
  • Anticatabolic action
  • Anabolic action

Low incidence of side effects (practice shows that irreversible side effects are almost completely absent) and a wide range of positive effects make clenbuterol one of the best fat burners in bodybuilding.

Some authors ( Yuri Bombela ) argue that in high doses, clenbuterol can have catabolic effects, but this is not true, due to the lack of any physiological or empirical justification.

Clenbuterol course: weight loss or drying

In men, the recommended dose of clenbuterol for drying and losing weight is 120 – 140 mcg per day. In women, the average dose of clenbuterol for drying and losing weight is 80-100 mcg per day. The course of clenbuterol has its own subtle features that must be strictly observed in order to avoid side effects.

The duration of the course of clenbuterol is usually 2 weeks, then addiction is developed (receptor tolerance) and the effectiveness decreases. Then you need to take a 2 week break using ketotifen , without it, the break is useless, and then repeat the course; without ketotifen, the break should be much longer. The need for a break was scientifically substantiated back in 1990: desensitization of beta-adrenergic receptors develops due to phosphorylation of receptors and through other biochemical modifications at the level of secondary messengers (kinases, G-proteins, etc.). It takes several days to update these structures.

The duration and effectiveness of the clenbuterol course, as mentioned, can be increased by the inclusion of ketotifen. Sometimes, to prevent adaptation of receptors, a pulse rate is recommended – 2 days of intake, 2 days of rest, but this scheme is less effective.

Remember to take enough protein , BCAAs, and other cortisol blockers throughout your cycle to dramatically improve your results. Follow an appropriate weight loss or drying diet .

In 2010, a study was conducted that revealed a synergistic effect when combined with anabolic steroids, which confirms the advisability of including the drug at the end of the course of the AU. Many experts do not recommend combining the drug with anabolic steroids, as the risk of cardiac hypertrophy increases.

Clenbuterol course without ketotifen 

  • day 1: 20 mcg (0.02mg)
  • day 2:40 mcg (0.04mg)
  • day 3: 60 mcg (0.06 mg)
  • day 4: 80 mcg (0.08mg)
  • day 5: 100 mcg (0.10 mg)
  • day 6-12: 120 mcg (0.12 mg)
  • day 13: 80 mcg (0.08 mg)
  • day 14:40 mcg (0.04mg)
  • break

The dose of clenbuterol should be progressively increased during the first week. The optimal time for taking clenbuterol is in the morning (so as not to provoke insomnia, moreover, the effectiveness of the drug is higher in the morning hours). When the dosage is increased, start taking it in 2 doses: in the morning and in the afternoon.

Course of Clenbuterol + Ketotifen 

Ketotifen is an antiallergic agent with a unique ability to restore the sensitivity of beta-2-adrenergic receptors to clenbuterol. This property has been proven many times in studies involving not only asthma patients, but also isolated lymphocytes. The mechanism of this effect is obviously associated not with histamine receptors, but inhibition of phosphodiesterase , which regulates cAMP-dependent metabolism of all cells, which allows extrapolating the results obtained in studies with lymphocytes to adipose tissue …

Similar effects of receptor re-sensitization have been observed with ketotifen in relation to other beta-agonists, which has been confirmed by a large number of studies.

With the help of ketotifen, you can speed up the process of losing weight or drying by 10-20 percent and extend the course up to 8 weeks. In addition, ketotifen will help eliminate mental agitation, limb tremors, insomnia and heart palpitations.

  • day 1:20 mcg of clenbuterol
  • day 2:40 mcg of clenbuterol
  • day 3: 60 mcg of clenbuterol
  • day 4:80 mcg Clenbuterol
  • day 5: 100 mcg Clenbuterol + 1 mg ketotifen
  • day 6-27: 120 mcg Clenbuterol + 2 mg ketotifen
  • day 28: 80 mcg Clenbuterol + 2 mg ketotifen
  • day 29:50 mcg Clenbuterol + 1-2 mg ketotifen
  • day 30: 33-35 mcg Clenbuterol + 1 mg ketotifen
  • at least two weeks off

Ketotifen is taken at night, clenbuterol – in the morning. The distribution of doses is the same as in the previous example.

Combination: To maximize the effectiveness of the course, clenbuterol is combined with thyroxine . However, in this case, the risk of side effects increases.

Side effects of clenbuterol 

The side effects of clenbuterol are listed by frequency of occurrence:

  • Palpitations (60%) – eliminated by beta-1-blockers. Take Bisoprolol 5 mg or Metoprolol 50 mg in the morning.
  • Tremors (20%) – especially pronounced on the first day of admission, then gradually fades away. Eliminated by ketotifen.
  • Sweating (10%)
  • Insomnia (7%) – eliminated by ketotifen
  • Anxiety (6%) – eliminated by ketotifen
  • Increased blood pressure (6%) – eliminated by beta-1-blockers. Take Bisoprolol 5 mg or Metoprolol 50 mg in the morning.
  • Stool disorder – diarrhea (5%) – usually observed only in the first days of taking the drug
  • Nausea (3%)
  • Convulsions (in case of overdose or at the initial stage of taking the drug)
  • In individual cases, a headache is possible, most likely associated with an increase in blood pressure.

As you can see, many of the side effects of clenbuterol can be prevented with ketotifen and bisoprolol (metoprolol). Also, it should be noted that most of the side effects are especially pronounced only at the initial stages of the course, and after a few days they subside or completely disappear.

It has been shown in animal experiments that large doses of clenbuterol can be toxic to the myocardium, and testicular tissue.

In Ostapenko’s book “Anabolic drugs” there is information that due to the accumulation of polyamines in cells, clenbuterol can cause a malignant process and lead to an increase in internal organs (in particular myocardial hypertrophy), which can explain the pronounced protrusion of the anterior abdominal wall in many modern athletes … However, there is no scientific and practical confirmation of these statements, so they can only be regarded as guesses of the author. In addition, it was determined that the increase in the abdominal cavity in professional athletes is associated primarily with the use of high doses of growth hormone .

Beta 2 receptors are also found in the kidneys, due to which there is an increase in renin secretion, which further leads to the excretion of potassium from the body, therefore, an additional intake of asparkam is considered advisable .

Clenbuterol slightly increases insulin secretion . Acting on the receptors of the intestine, it causes its relaxation, which can affect its function: incomplete digestion of food, diarrhea, flatulence, dysbiosis.

The information in some instructions on bronchospasm after withdrawal is relevant only for people with asthma, in whom the reaction of the bronchial tree is increased.

Caffeine , yohimbine, thyroxine, and other stimulants significantly increase the incidence of side effects.

Clenbuterol and alcohol

It is not recommended to combine clenbuterol and alcohol, as this can increase nausea and palpitations. Clenbuterol and alcohol increase the stress on the cardiovascular system. In addition, alcohol interferes with weight loss and drying. Alcohol destroys muscles. Read the main article: Alcohol and Muscle.