3 ms·

It doesn't take much caffeine to produce fasciculation (specially on facial muscles) in some people, for instance.

• Produce 15y ago
  That doesn't indicate neurotoxicity though. Involuntary movements are caused by excess dopamine and are seen in people who use too much L-Dopa (dopamine precursor) for extended periods of time, for example. Interestingly, this effect is blocked when co-administering and NMDA antagonist. Even more interestingly, NMDA antagonists have been observed to reduce/prevent stimulant tolerance. All of this suggests that it's possible that involuntary movements are simply dopamine deficiencies (e.g. in the case of L-Dopa, dopamine receptors down-regulate too much). Caffeine is known to release significant amounts of dopamine. Over a period of time, this will down-regulate dopamine receptors.