There are many methylxanthines, but only tow other, theophylline and theobromine occur naturally and are widely self-administered.
Although methylxanthines occur naturally in many species of plant, the most common sources are tea, coffee and chocolate. They are also found in many over-the-counter painkillers, cold remedies and stimulants.
After drinking tea or coffee, peak levels of caffeine in the blood are reached between 30-60 minutes later. However, there is some evidence that caffeine in cola beverages are absorbed more slowly and reach their peak around two hours later.
Commonly believed to be an aphrodisiac, it was used at wedding feasts and by rich noblemen who had many wives.
Following the spanish conquest of central and south america, the roman catholic church banned the use of the drug because of it’s reputation as an aphrodisiac but the ban did not last.
Chocolate was introduced to the Spanish court in 1520. The spanish added vanilla and sugar instead and the sweetened form of chocolate became popular across Europe.
Methylxanthines compete with adenosine for the receptor sites, consequently, adenosine is prevented from exerting its inhibitory action, resulting in the stimulation of the CNS. Caffeine is a stimulant drug and also a diuretic.
Relaxation of smooth muscle causes dilation in the bronchi in the lungs and a subsequent decrease in airway resistance. Consequentally, theophilline is used clinically in the treatment of asthma.
The subjective effects of caffeine include elevated mood, feelings of alertness, the ability to concentrate and the ability to overcome tiredness.
There have also been concerns with the amount of caffeine you children have been consuming though soft drinks and chocolate.
Lower doses, four to five cups per day, over a long period of time is also sufficient to cause dependence.
Symptoms of caffeine withdrawal include: headache, fatigue, lethargy and agitation which may last up to a week.
There have been at least six deaths recorded due to caffeine overdose. The lethal dose in humans is equivalent to 30-80 cups of coffee. Death results from convulsions and respiratory collapse.