ftp.cse.unsw.edu.au/2014.06.ftp.cse.unsw.edu.au.tar/ftp.cse.unsw.edu.au/pub/doc/misc/Caffeine

Internet Message Format | 1992-10-18 | 6KB

Path: spinifex!elecvax!usage!basser!john
From: [e-mail] (John Mackin)
Newsgroups: aus.followup
Subject: caffeine
Summary: There's no room in the drug world for amateurs.
Message-ID: <[e-mail]>
Date: 4 Oct 88 18:44:56 GMT
References: <[e-mail]> <[e-mail]>
Organization: Dept of Comp Sci, Uni of Sydney, Australia
Lines: 115

I thought it was time to inject a few facts about caffeine
into this discussion, in line with the Summary: header.
The following is quoted from _Pharmacology: An Introduction
to Drugs_, by M. C. Gerald, Prentice-Hall, 1974, pp. 277-280,
with deletions; where I have paraphrased for brevity I
have indicated that with [square brackets].

John, who's soaking in it.

What accounts for the world-wide popularity of coffee, tea, cocoa,
and cola-containing soft drinks?  Undoubtedly, we drink these
beverages, consciously or unconsciously, for the ``lift''
they provide.  These stimulating properties are attributed to
caffeine, a naturally occurring alkaloid (Table 15.1).
Coffee's popularity may be documented by simply pointing
out that three billion pounds are consumed annually in the
United States.


Table 15-1.  Caffeine content of popular beverages and their
         natural sources.

   Beverage        mg Caffeine         Natural Source    % Caffeine

Coffee                     Coffea arabica    1-2
  Regular      100-150 per cup    (coffee bean)
  Instant      60-80    per cup
  Decaffeinated      2-4 per cup
Tea          25-75    per cup         Thea sinensis     2
                     (tea leaf)
Cocoa          up to    50 per cup   Theobroma cocoa   0.1-0.4
                     (cocoa seed)
Cola beverages      30-50    per 12 oz    Cola acuminata    2
                     (kola nut)


Caffeine and the chemically related xanthines, theophylline
and theobromine, are stimulants of the central nervous system.
In addition, they are capable of stimulating skeletal and
cardiac muscle, relaxing the smooth muscle of the bronchioles,
and increasing respiration and producing diuresis.

Pharmacological Effects

Caffeine is a potent central nervous stimulant, which, with
progressively increasing concentrations, activates the cortex,
then the medulla, and, in toxic doses, the spinal cord.
When administered in doses of 50-200 mg, the equivalent of
one-half to two cups of coffee, we note enhanced mental
alertness with a reduction in drowsiness and fatigue
[and a] lengthen[ed] attention span.  The performance of
simple tasks adversely affected by boredom and fatigue is
improved, but these findings are complicated by highly
subjective factors such as motivation.  Increasing the dosage
of caffeine above 200 mg does not further increase mental and
physical performance but rather has a detrimental influence
because of such adverse effects as nervousness, irritability,
tremors, and headache.

Caffeine is capable of strengthening the force of contraction
of voluntary muscle, as well as reducing the ability of such muscle
to become fatigued.  Laboratory experiments with human subjects
have demonstrated that caffeine permits an individual to carry out
physically exhausting work for longer periods of time.

The heavy coffee drinker becomes psychically dependent upon
caffeinated beverages.  Such an individual generally
requires one or two cups of coffee in the morning before
he can exhibit his normally agreeable disposition.
[Upon withdrawal] a clearly demonstrable abstinence
syndrome is not observed.  The withdrawal symptoms
are relatively mild and are characterized by irritability,
nervousness, and headache.  [Tolerance develops;]
150 mg of caffeine added to decaffeinated coffee
disrupted the normal sleep patterns of nondrinkers,
whereas it was without effect in habitual coffee drinkers.
Similarly, chronic use reduces the ability of these
compounds to enhance alertness.

Toxicity and Adverse Effects

Caffeine is generally considered to be a relatively nontoxic
compound.  One fatality has been reported after an intravenous
dose of 3.2 g, and it has been estimated that 10 g of caffeine
would have to be taken orally to produce death.  Doses larger
than 1 g produce excessive CNS stimulation resulting in
irritability, insomnia, excitement, muscle twitching,
and convulsions.  [These CNS effects] can be readily managed
with short-acting barbiturates.  [Children are more sensitive
to caffeine] than adults, and therefore it is probably wise
to omit [caffeinated beverages] from their diets.
[Caffeine consumption is contraindicated in the presence of
peptic ulcers, heart disease, and hypertension.]

Clinical Uses

The xanthines, theophylline in particular, have proved to be
valuable drugs for the treatment of such respiratory diseases as
asthma, bronchitis, and emphysema.  These drugs are able to
relax the smooth muscles of the bronchi, thereby relieving the
wheezing and other breathing difficulties associated with these
diseases.  These agents, by virtue of their direct stimulatory
effects on the heart muscle, have been employed for the treatment
of heart failure.  In mild cases of central nervous depression
resulting from fatigue or a modest overdose of sedative-hypnotics,
tranquilizers, or antihistamines, several cups of strong, black
coffee have beneficial stimulatory effects.

Amphetamine is among the most effective antifatigue drugs,
yet this agent has great abuse potential, and it can only
be legally procured with a physician's prescription.
To fill the need of those attempting to combat fatigue,
[many different non-prescription stimulants are available,
consisting of caffeine in doses of from 65 to 200 mg per
tablet].