Shift workers are taking drugs to help them stay awake or get to sleep despite weak evidence for their benefit, researchers said.
The authors of the review found only small numbers of trials testing over-the-counter and prescription drugs used by shift workers, and the results suggest that for some people they might do more harm than good.
In most developed countries, at least 10 per cent of the workforce is involved in some form of shift work.
Disturbances to normal sleeping and waking patterns increase the risk of accidents and affect shift workers' health.
"It is therefore important to avoid shift work where possible and improve shift work schedules to help shift workers achieve more normal sleeping and waking patterns," researchers said.
In jobs where shift work cannot be avoided, such as health care, the police force or the military, drugs can potentially offer short-term benefits.
The review included 15 trials involving a total of 718 people. In nine trials, the over-the- counter hormone drug melatonin helped shift workers sleep for around 24 minutes longer during the night or day, compared to placebos. However, it did not help them get to sleep any quicker.
Data from only one trial of the hypnotic drug zoplicone was available. The drug was no more effective than placebos for helping shift workers sleep during the day.
The remaining trials focused on caffeine and two drugs, modafinil and armodafinil, that are prescribed for sleepiness during night shifts.
In one trial, caffeine reduced sleepiness during night shifts, when workers also napped before shifts. Modafinil and armodafinil, used by shift workers in one and two trials respectively, increased alertness and reduced sleepiness.
However, they also caused headaches, nausea and a rise in blood pressure in a substantial number of people.
"For lots of people who do shift work, it would be really useful if they could take a pill that would help them go to sleep or stay awake at the right time," said lead author of the review, Juha Liira, who is based at the Finnish Institute of Occupational Health in Helsinki, Finland.
"But from what we have seen in our review, there isn't good evidence that these drugs can be considered for more than temporary use and some may have quite serious side effects," said Liira.