Caffeine Flashcards
High absorption from
oral doses
Caffeine half life
~ 4 hour
caffeine is a
Stimulant and anxiogenic
caffeine structure
xanthine alkyloid
Caffeine is structurally analogous
to the neuromodulator
adenosine
- Related xanthines are
found in
many plants
Behavioural effects of caffeine - In animals caffeine has a
biphasic effect
In animals caffeine has a biphasic effect
Increased locomotion at low dose
Decreased locomotion at high dose
In blinded studies vs placebo caffeine (in abstinent coffee drinkers)
increased alertness
and decreased tension,
decreased reaction times
Therapeutic uses of caffeine - OTC analgesics
- Caffeine has been shown
effective at treatment for nonmigraine headache
Therapeutic uses of caffeine - * Apneic episodes in newborns
Periodic cessation of breathing,
common in premature infants -Principal treatment is caffeine or
theophylline
caffeine TOLERANCE
Tolerance develops to some subjective effects of caffeine
Acute tolerance allows one to
o fall asleep after a late-night
cup of coffee
Physiological and psychological symptoms of
withdrawal
Headache, lethargy, fatigue
Impaired psychomotor performance
Mild anxiety or depression
- If abstinent withdrawal may last a
a few days before
dissipating
DEPENDENCE
Caffeine can excite the mesolimbic DA pathway but
only at very high doses
dependence doses
- 5-10 X above ‘normal’ doses
DEPENDENCE is
Well demonstrated but considered relatively harmless
Behavioural / psychological dependence (not
pharmacological) plays a significant role in
reinforcing
effects of caffeine
Most chronic coffee drinking is to provide
relief of
withdrawal
Withdrawal from caffeine
induces
transient
subjective effects
caffeine - placebo - caffeine (headache)
reduced headache in caffeine - increased headache immediately after during placebo phase reduced after 2 days - reduced headache during caffeine
caffeine - placebo - caffeine (concentration)
high levels of concentration - initial decline following by increase - further increase
caffeine - placebo - caffeine (lethargy)
low levels of lethargy - initial increase followed by decrease - further decrease
caffeine - placebo - caffeine (energy)
increased energy - initial decrease followed by increase - increased energy
Biochemical effects - Caffeine acts at many sites in the CNS
including
GABAA receptors and eliciting
Ca2+
-release within cells
Caffeine acts at many sites in the CNS
including GABAA receptors and eliciting
Ca2+
-release within cells, but most likely
exerts stimulant effects by
antagonising
adenosine receptors.
Adenosine is elevated in the cat brain
after periods of long
wakefulness (sleep
deprivation) and is suggested to signal
increased sleep pressure
Blockade of adenosine receptors reduces
drowsiness.
Adenosine
Among other roles, adenosine provides
inhibitory input to ascending arousal
systems
Adenosine Inhibitory at multiple sites in the
hypothalamus
Adenosine Inhibitory at multiple sites in the hypothalamus
- Suprachiasmic nuclei (SCN)
- Lateral hypothalamus (LHA)
- Preoptic areas (MnPO, VLPO)
Adenosine release inhibits
arousal and
increases sleep pressure
