| Abstract: | The effects of 4 mg/kg and 8 mg/kg caffeine nocte as a model of insomnia, and its potential for reversal with an hypnotic (temazepam 20 mg) were investigated in two double-blind placebo controlled crossover studies, each with six healthy volunteers. Following an adaption night and day, two nights per treatment were assessed with multiple sleep latency tests (MSLTs), performance measures and subjective questionnaires undertaken the following day. In comparison to placebo significant (P < 0.05) increases in sleep onset latency of 30 and 40 min were seen for low and high doses respectively. Significant reductions in sleep duration were limited to the higher dose (total sleep time 80 min, sleep efficiency 17 per cent), as were reductions in slow wave sleep and non-REM sleep which contrasted with increased waking. However, contrast analysis revealed significant dose-related effects for these measures, whilst the lower dose produced more stable effects across nights, suggesting it as more suitable for a model of insomnia in healthy sleepers. Significant decrements in critical flicker fusion (CFF) performance and reduced MSLT latencies reflected increased daytime sleepiness following both doses; although significant subjective changes to sleep and sleep tendency next day were limited to the higher dose. Co-administration of temazepam elixir successfully reversed increased sleep latency seen with the lower caffeine dose and improved subjective sleep, but significant effects on other sleep measures were more limited despite improved mean trends. Similarly, improvements in CFF performance and MSLT latencies failed to achieve significance, suggesting a possible limitation of the hypnotic in overcoming the effects of sleep disturbance and consequences for waking function next day. |
