The Contribution of cocoa additive to cigarette smoking addiction

RIVM report 650270002 Page 29 of 207
Caffeine
Critical assessment
Comparison of smoking related daily consumption with daily consumption of
caffeine (mg) from other sources:
SMOKING DRINKING OR EATING
25 cig. 3 3 3 3 3
(1% cocoa) Coffee Tea Chocolate Chocolate Cocoa
drinks drinks bars of 60 g drinks .
Caffeine (mg) 0.5 186 (12) 95 (12) 12 (12) 40 (milk) (13) 15 (1)
240-405 (9) 36 (milk) (14)
12 (sweet) (15) .
Little is known about the profile of the pyrolysis/combustion products of caffeine.
Conclusion
The daily intake of caffeine from cigarettes through inhalation is marginal compared
with the oral intake of caffeine from other sources, like coffee, tea, chocolate drink
and sweets. So, the plasma concentration reached after ingestion of caffeine from
coffee, tea or chocolate sources is expected to be significantly higher, than after
intake from cigarettes. However, the different route of application via smoking as
compared to other sources should be taken into account. Therefore, local effects of
caffeine on the respiratory system might be a point of concern.
PHARMACODYNAMICS
Mechanism of action
It was initially thought that caffeine and other methylxanthines acted primarily as
phosphosdiesterase inhibitors. However, the inhibition is minimal at typical serum
levels. At present it appears that the most important mechanism of action of caffeine
is the antagonism of adenosine receptors. Adenosine is a locally released purine
hormone that acts on two different receptors, A1 and A2. Receptors mediate either an
increase or a decrease in cellular concentrations of cyclic adenosine monophosphate.
High affinity (A1) receptors inhibit adenylate cyclase; low affinity (A2) receptors
stimulate adenylate cyclase. Adenosine receptors are found throughout the body,
including the brain, the heart and bloodvessels, the respiratory tract, kidneys, adipose
tissue and the gastrointestinal tract. Adenosine acts locally as a vasodilator. It also
reduces platelet aggregretion in vitro, inhibits catecholamine and renin release and
inhibits lipolysis. Caffeine nonselectively inhibits the action of adenosine (9).
Pulmonary system
breathing frequency: The respiratory rate correlates closely with the plasma
caffeine level ( 250 mg oral intake) (9). The major respiratory effect of caffeine
(ingested from coffee) is an increased output of the respiratory centre. In healthy
subjects caffeine (650 mg ingestion) significantly increases ventilation at rest,
accompanied by a fall in an end tidal carbon dioxide tension (16).
tidal volume: Caffeine increased the tidal volume during exercise after ingestion
of 3.3 mg/kg body weight (17) or after 650 mg ingestion (18).
lung compliance: The expired ventilation volume increased significantly after
caffeine ingestion (18, 19).
airway resistance: Caffeine has a bronchodilatory effect in humans through oral
.