• Active-Life: Up to 4 days
  • Drug Class: Beta-2-symphatonimetic, thermogenic, possible anticatabolic (Oral)
  • Average Reported Dosage: Men 60-200 mcg per day Women, half that
Let me just start by saying that this is the single most mis-understood compound in use for athletics and bodybuilding today. Most of the information out there is Ѕ truths and conjecture. Ok…having said that, I’m going to make an effort to dispel some myths and give everyone a better understanding of Clen.

First, lets plow quickly through some of the basics:

Clenbuterol (Clen) is a selective beta-2 agonist/antagonist and a bronchodilator. What this means, is that it stimulates your beta-2 receptors. And this in turn stimulates you (clen has stimulant effects which will make you feel….well…stimulated). All of this serves to increase your body temperature a bit, increase your basal metabolic rate, and decrease your appetite (Int J Obes Relat Metab Disord. 1994 Jun;18(6):429-33.). Clen also can decrease insulin sensitivity (Am J Physiol Endocrinol Metab. 2002 Jul;283(1):E146-53.).

Clen is a very effective repartitioning agent, and this is what it’s most often used for. What this means is that it will increase your ratio of Fat Free Mass (FFM) to Fat Mass, by decreasing your Fat and possibly increasing your FFM (J Appl Physiol. 2001 Nov;91(5):2064-70). Want me to quantify that a bit? In one study, horses given a semi-reasonable dose of clen (slightly over 1mcg/lb x2 a day) and excercised for 20mins, 3x a week ( I suppose they were Mentzer disciples) had significant decreases in %fat (-17.6%) and fat mass (-19.5%) at week 2, which was similar to Clen given to horses who didn’t excercise; however, the excercised group had a different FFM response, which significantly increased (+4.4%) at week 6. Week 6! Clen and clen+excercise produce roughly the same results for the first 2 weeks! Remember the old 2 weeks-on/2weeks-off schedule? It’s officially dead and buried. If you want the quasi-anabolic effect from the clen, it’ll take more than 2weeks on (6 weeks apparently). And in fact, since clen alone is similar to clen+excercise for those first 2 weeks...why would you ever use a 2on/2off protocol? Keep in mind that animal responses to beta-agonist/antagonists differ a bit from ours…but you get the picture. 2on/2off? Ha ha...

Clen has a biphastic elimination, which means that it is technically reduced in your body in 2 different stages. This isn’t particularly important, as a recent study has shown that for most intents and purposes, clen concentrations in the body decline with a Ѕ life (approximately) equivalent to 7-9.2hours and again up to as much as 35 hours later(J Anal Toxicol. 2001 May-Jun;25(4):280-7. and J Vet Pharmacol Ther. 2004 Apr;27(2):71-7. and J Pharmacobiodyn. 1985 May;8(5):385-91. ). If you’re really interested, though, clen technically declines biphastically at 10 and then 36 hours. But really, in our little world, where we use Ѕ life to tell us when to take our next dose, who the hell is going to take clen, then a dose 10 hours later, then a dose 36 hours later. We’ll stick with the earlier 7-9 hour Ѕ life for dosing purposes, and take our clen every 3.5-4.5 hours that we’re awake, stopping early enough to still be able to get to bed. Clen can, in some people, cause insomnia (and as with all stimulants, can cause anxiety in some).

Clenbuterol can also cause a downregulation in testicular androgen receptors and in pulmonary, cardiac and central nervous system beta-adrenergic receptors(J Anim Physiol Anim Nutr (Berl). 2004 Apr;88(3-4):94-100.)…possibly making steroids less effective (if there is androgen receptor downregulation elsewhere as well, then it's highly probable) while you are on clen; but definitely making clen less effective as time goes on and you keep taking it. To counteract this, you can take some ketotifen or periactim every 3rd or 4th week that you remain on clen. Both of these are prescription anti-histimines, so they’ll make you drowsy (take before bedtime). Basically, the way both of these work is to reduce beta-2 receptor activity.

Another option, if you are worried about receptor downgrade, is taking Benadryl, at around 50-100mgs/night before bed (every 3rd week or so, for that week). Benadryl is sold as an anti-histimine in the United States, and/or a sleep aid elsewhere in the world. However, Beta receptors are embedded in the cell's outer phospholipid membrane. The stability of the membrane has a lot to do with the proper function of the receptors. Methylation of the phospholipids is stimulated by the binding of beta agonists to their receptors. Methylated phospholipids are foreign to the body, and when the body recognizes tham as foreign, it breaks them down with phospholipase A2. This changes the structure of the outer membrane which results in desensitizaton of the beta receptors. On the other hand, agents that inhibit phospholipase A2 slow desensitization.

Cationic ampiphylic drugs are known for their ability to inhibit phospholipase A2. Benadryl (diphenhydramine) is a cationic ampiphylic drug.

Ergo, Benadryl slows desensitization of Beta receptors (i.e. Upgrades them) by inhibiting phospholipase A2, which is the enzyme that breaks down methylated phospholipids, and this action in turn keeps the phospholipid membrane stable, and thus keeps the receptors functioning properly. (Prog Clin Biol Res. 1981;63:383-8). This will allow you to use clen for much longer and it'll still have the same effects.

A lot of people claim that clen is quite anti-catabolic and/or anabolic. This hasn’t been confirmed in human studies (Ann Pharmacother. 1995 Jan;29(1):75-7.). And the doses given to the animals in these studies where clen is shown to be very anticatabolic or highly anabolic are so absurdly high that no human could ever take them (1mg/kg of bodyweight and higher). The best you can hope for is the very mild anabolic effects I cited earlier.

Oh yeah…I guess I should get around to the proper dosing of clen. My recommendations are the same for both men and women. You’ll need to take 20mcgs upon rising, and then repeat that same dose again later in the day, and then once again in that day (if you find you can tolerate the effects). So you’ll start with 20mcgs, and then repeat that dose 2 more times that same day if you can tolerate it (side effects will determine this…hand shaking, sweating, etc…classic stimulant sides). Then you can start increasing the dose gradually. Personally, I wouldn’t work my way up to more than 200mcg/day. 60-120mcg/day is an average dose. And keep your Blood Pressure at (or under) 140/90, while on clen, ust to be safe. If you go over that, lower the dose.

Also, bear in mind that clen isn’t great for your heart, and can cause some issues there (enlargement of ventricles, etc…) but most studies showing clen to cause heart problems are with animals, and even though the dosing is almost similar to what humans take (in some studiesits within range of what would be double of a large himan dose...) it’s important to remember that animals have more beta-2 receptors and they cause certain event chains that humans’ beta-2 receptors may not. Clen causes cardiac hypertrophy to some degree, in some cases. Again though, many studies showing more significant heart problems are with mg dosing. We humans take clen in mcg doses.

If we want to duplicate the “theraputic” levels of clen in the more conservative studies, we’d be taking just over 1mcg/lb of bodyweight. I’d suggest a bit less, though.

Performance issues with clen also vary. Some studies show reduced exercise (cardiovascular) performance with clen (Med Sci Sports Exerc. 2002 Dec;34(12):1976-85.), while some show that clen can alleviate exercise induced asthma (Respiration. 1987;51(3):205-13.)! Sometimes you feel like a nut…sometimes you don’t, I guess. What this means, to me, is that you’ll need to figure out how clen affects your performance individually.

Which brings me to the issue of cramps while on clen. I don’t get them. My friends don’t get them. Most of us are athletes who use clen during the season as well as the off season, and one of my friends even claims that it gives him more “wind” (cardiovascular stamina). Take on enough water every day and you should be fine. If you’re really concerned, you can take some extra minerals and taurine, since clen depletes taurine (Adv Exp Med Biol. 1996;403:233-45) as do most if not all beta-agonists. I don’t take anything more than my usual vitamins and minerals.