Caffeine | How it works, Pharmacological effects, Overdose, Headache

Methylxanthines

Various beverage contain methylxanthines such as tea, coffee, cocoa, and soft drinks. It has mild central stimulant effect

The main compounds are caffeine and theophylline. It is also known as analeptics

The average caffeine consumption in beverages is 200 mg /day

Methylxanthines mechanism of action

They act as antagonists of adenosine receptors where both A1 and A2 receptors are affected.

Adenosine receptors are located on pre-synaptic terminals of noradrenergic neurons and blocks noradrenaline release. Hence, caffeine increases NA (noradrenaline) release.

Also, inhibition of phosphodiesterase may occur but only at very high doses.

Peripheral actions are exerted mainly on heart, smooth muscle and kidney.

How Caffeine Works

Adenosine helps prepare the body to sleep by curbing the chatter between nerve cells and by widening blood vessels to increase the flow of oxygen.

Receptors on the surface of brain cells can't tell the difference between adenonsine and caffeine (competitive inhibitor). So when you consume caffeine, it attaches itself to the receptors and adenosine is shut out.

Without adenosine to make you sleepy, your brain activity perks up and you become more alert. By blocking adenosine, caffeine also constricts your blood vessels, which has the ability to make your headache disappear.

Caffeine pharmacological effects

At central nervous system, caffeine stimulate cortex first, followed by medulla and spinal cord at high doses.

The main effects are reduced fatigue & improved mental performance (improved concentration and clearer flow of thought) without euphoria

Other major pharmacological effects are

·         diuresis

·         stimulation of cardiac muscle

·         relaxation of smooth muscle especially bronchial muscle