The term "anhydrous" is chemistry lingo for "without water." So, caffeine anhydrous is essentially "dehydrated caffeine." Since caffeine is water-soluble and abundant in certain plants and seeds, especially coffee beans and tea leaves, it naturally exists in liquid phases.

During the caffeine extraction process, it is dehydrated to remove the water content. This yields a highly concentrated caffeine powder, and voila! You have caffeine anhydrous.Transparent Labs Stim Booster

The important thing to grasp is that caffeine anhydrous is the same as "natural caffeine." Caffeine is a discrete chemical — dehydrating it doesn't change how it works in the body. It might help to think of caffeine anhydrous as "caffeine powder" made from natural caffeine.

You might even find it surprising that caffeine anhydrous is more effective than drinking caffeine from coffee, particularly for athletic performance (2). It’s not entirely clear why this is, but it’s plausible that other compounds in coffee render the caffeine less effective.

HOW DOES CAFFEINE WORK?
Caffeine — or 1,3,7-trimethylxanthine, for the organic chemists out there — is a naturally occurring, alkaline substance that belongs to a group of compounds known as methylxanthines. Other lesser-known methylxanthines found in the typical human diet include theobromine and theophylline.

Your body — primarily the liver — actually metabolizes caffeine almost entirely to theobromine, paraxanthine, and theophylline (3). Hence, very little caffeine ever makes it into the urine.

These natural methylxanthines are all responsible, to varying degrees, for how caffeine works in the body. As you well know, caffeine is a potent stimulator of the central nervous system (CNS), eliciting the patent mood-lifting and vigilance-enhancing effects people crave after their last cup of coffee wears off.

Physiologically speaking, caffeine and its related methylxanthines act as adenosine receptor antagonists, as well as acetylcholinesterase (ACE) and phosphodiesterase (PDE) enzyme inhibitors (4).

Without making this too complicated, caffeine works primarily by binding enzymes and adenosine receptors, thereby blocking their actions. These are molecules that normally "put the brakes" on your CNS. Therefore, caffeine and other natural methylxanthines are "stimulants" since they speed up neural activity.

As far as your neurons can tell, caffeine is indistinguishable from the adenosine your body naturally produces on its own. Pretty neat, right? Caffeine is a master of disguise!

EFFECTS OF CAFFEINE
Your brain and spinal cord (i.e., CNS) are the quintessential command center of the rest of your body. For example, when your brain consciously tells your muscles to contract to lift a weight, neurons transmit the "input signal" to the designated muscles.

Electrochemical gradients, chemical messengers (neurotransmitters), and cell messengers govern these signals. Caffeine and related methylxanthines alter the way these gradients and messengers work to keep your neurons "excited."

The primary short-term effects of this are:

Increasing resting heart rate
Psychostimulation (i.e. feeling "wired")
Constricting blood vessels
Dilating the bronchioles
Slightly increasing metabolic rate
Increasing urine production and gastric motility