The effects of 600 mg of slow release caffeine on mood and alertness

Caffeine is the most widely used psychostimulant.

This study evaluated the pharmacokinetics and effects of mood and alertness of a single oral administration of 600 mg of a slow release caffeine (SRC) on a large group of healthy subjects.

In this double-blind, parallel-group study, 120 young adult males were randomly assigned to either a caffeine group (CG, n = 100) or a placebo group (PC, n = 20). After a normal sleep, each subject took 600 mg of a SRC or a placebo. Circulating caffeine was determined by salivary caffeine assays after acetylation phenotype categorization. Mood, alertness and nocturnal sleep were evaluated by visual analog scales (VAS).

This SRC was well tolerated probably due to its relative low plasmatic Cmax (10.37 micrograms.ml-1). Between CG and PG, there were no differences for alertness, contentedness and sleep quality of the night after treatment (N2) compared to the previous night (N1). VAS scores showed a decrease in calmness in the CG (p < 0.01). Sleep latency in N2 was significantly increased with caffeine (p < 0.01). Calmness, sleep onset latency, quality of sleep onset and overall rating of N2 compared to N1 were correlated with caffeine levels, which were only influenced by tobacco consumption.

Although a single oral dose of 600 mg of a SRC is well tolerated, further evaluation must be done on alertness and pharmacokinetics with fatigued subjects and with females using oral contraceptives.