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Clenbuterol and Side Effects – part 1

What is Clenbuterol?
Interestingly, Clenbuterol was not actually developed to be a weight loss drug at all.  In fact, it was designed for the treatment of such breathing disorders as asthma.  However, in spite of the fact that clenbuterol is used throughout the world, the U.S. FDA has never approved its use for the treatment of asthma.  Instead, Albuterol is prescribed in the U.S. when a patient is in need of a bronchodilator, where clenbuterol would be very effective.

clenbuterol balkan-pharmaceuticals

Fig 1. Clenbuterol by Balkan Pharma

Table of Contents

How it works

Clenbuterol works by stimulating the sympathomimetic nervous system, particularly the beta-2 receptors.  This stimulation actively reverses airway obstructions and provides improved breathing, which is a very positive effect for asthmatic patients and athletes who benefit from enhanced cardiovascular endurance.  What’s more, this same stimulation can be also used to enhance the metabolic rate of the individual, since beta-2 stimulation causes the mitochondria of the cells to produce and release more heat.  In turn, this heats up the body’s temperature, up regulates the metabolism and causes the individual to burn body fat at a higher rate.

Unfortunately, clenbuterol is often incorrectly recognized for having strong anabolic properties because studies have shown that clenbuterol has the ability to promote anabolic activity in rats.  This has caused many bodybuilders to use the compound in their post cycle therapy (PCT) or in hopes of gaining lean muscle tissue.

Nonetheless, there is no data supporting such findings in the case of human beings, so clenbuterol use in humans is only justified as a bronchodilator or as a thermogenic compound.

Furthermore, in spite of being a powerful fat loss agent, clenbuterol will not make a fat physique lean on its own.  Therefore, if you are obese or significantly overweight, your best bet is to leave clenbuterol use for later.  Hence, the optimal time to use Clenbuterol is once you’re already lean and in an effort to help you get rid of that last little body fat that often hangs on for dear life.

Dosages of Clenbuterol

Due to the body’s incredible ability to adapt to clenbuterol, dosages will need to be increased throughout the cycle.  Most individuals will begin with a starting dose of 20-40 micrograms (mcg) per day for 2-3 weeks.  At the end of the 2-3 week period, the user will increase the dose by 20mcg and hold that dose for another 2-3 weeks.  From here, the dosage will be increased by 20mcg every 2-3 weeks until the diet or cycle comes to an end.  Nevertheless, the maximum clenbuterol dose I ever recommend using is 120mcg per day, and no one for any reason should ever surpass the 140mcg daily mark.

This dosing format will keep the metabolism revved throughout the entire cycle and there will be no period in the diet where the athlete won’t enjoy the metabolic enhancement. What’s interesting, many users inaccurately assume that when the stimulating effects of clenbuterol begin to fade, the thermogenic effects are no longer working.  This is not true, as literature suggests that the same dose of clenbuterol can actually keep the metabolism revved for as much as five weeks.

Regarding the cycle duration, no matter what dosages are taken, clenbuterol use should be limited to a maximum of 16 weeks per year.  Those competing in more than one show per year can split the 16 weeks into two 8-week cycles.


Ketotifen is a medically used anti-histamine to treat asthma and allergies.  What’s relative to this article is that ketotifen has been shown to inhibit the down regulation of the beta 2 receptors caused by clenbuterol.  Consequently, you can continue taking clenbuterol for a longer period of time without having to cycle off to regenerate the receptor sensitivity by adding ketotifen.  Additionally, it means that you don't need as much clenbuterol to get the same benefits.  Although no studies have been done to find the most effective dose of ketotifen for this purpose, most users find a daily dose of 2-3 milligrams (mgs) to be ideal, and this dosage can be split or taken in one sitting.  Meanwhile, higher doses are likely to cause drowsiness and increased appetite that can be sometimes severe.

Ketotifen clenbuterol

Fig 2. Pharma Ketotifen

I personally feel that ketotifen supplementation is only necessary for the professional physique athlete doing multiple shows per year with very minimal time off from clenbuterol between shows.

Side Effects of Clenbuterol

The side effects of clenbuterol come from its stimulating nature.  Therefore, the most common side effects surround a jittery feeling, shaky hands and increased sweating.  Besides, the side effects will usually be very pronounced during the early stages of use.  Luckily, as the individual becomes accustomed to the stimulant, these side effects should begin to subside somewhat.

Moreover, one of the more bothersome side effects of clenbuterol are muscle cramps.  Even though these cramps are not exceedingly common, they will affect many people, especially at the dosages of clenbuterol seen closer to the end of the cycle.  Staying well hydrated is often enough to avoid or remedy this problem, but supplementing with the amino acid taurine and making sure that sufficient electrolytes are being consumed daily (sodium, magnesium, calcium and magnesium) can also help.

Additionally, clenbuterol supplementation often brings issues with insomnia.  This happens because clenbuterol has a 34-hour half-life, which can make sleep impossible for some people.  Hence, it is best to supplement with clenbuterol first thing in the morning, which will often help with the insomnia, but due to the long half-life some users will face insomnia regardless of when they take it.

Finally, when used at high doses and for extended periods of time, clenbuterol can bring upon severe side effects, including high blood pressure, irregular heartbeat, trembling and even panic.  As a result, clenbuterol abuse can cause cardiac hypertrophy, which could potentially lead to death.


Want to read about Clenbuterol on our forums? check out these threads:

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Trevor Kouritzin is a Canadian Natural Professional Bodybuilder and International Model. Mr. Kouritzin is also a Chemical Engineer and currently is a Human Nutrition MSc Candidate, he will be working on his PhD this coming year. Currently, he is conducting research on dietary supplements at prestigious universities throughout North America.

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