A small controlled narcolepsy study reported reduced sleep tendency and fewer errors on a simple computerized driving task after methamphetamine. Its clinical population, unequal group doses and simplified task prevent direct conclusions about real-world driving safety.
The 1993 study included eight adults with narcolepsy and eight matched healthy controls. Active-drug and placebo conditions used double-blind randomized crossover procedures. Each treatment condition lasted four days with intervening washout periods.
Participants with narcolepsy received 20 mg or a pooled high-dose condition of 40–60 mg; controls received 5 or 10 mg. The two groups therefore were not compared at equal doses. The high-dose protocol was also increased after the first five patient pairs and pooled for analysis.
For participants with narcolepsy, mean multiple-sleep-latency-test latency increased from about 4.3 minutes on placebo to 9.3 minutes in the high-dose condition. Errors on the Steer Clear task decreased markedly.
Steer Clear displayed a cartoon car and obstacles, with lane changes made by pressing a keyboard space bar. It tested sustained responding in a monotonous task. It did not reproduce traffic judgment, vehicle control or the full demands of on-road driving.
The investigators measured methamphetamine in serum approximately two and eight hours after dosing. Serum concentrations, task performance and sleep tendency are distinct endpoints; their group relationships did not validate a universal blood impairment or safe-driving cutoff.
High-dose treatment also reduced nocturnal sleep efficiency, and some patients still had abnormal sleep tendency. The authors noted possible carryover, short treatment periods and unresolved long-term safety. Their findings describe a therapeutic experiment in selected patients, not proof that methamphetamine generally improves driving or that similar concentrations imply the same functioning in another person.
Read our analysis of a separate controlled simulated-driving study.
Treatment of Narcolepsy with Methamphetamine. doi:10.1093/sleep/16.4.306.