CNS effects of indomethacin: should patients be cautioned about decreased mental alertness and motor coordination?

In many European countries as well as in the USA, the leaflet, or even the packaging of indomethacin, contains a specific warning to refrain from activities requiring mental alertness and motor coordination, such as driving a car. In this placebo-controlled randomized study with a crossover design we attempted to find evidence for that warning.

Indomethacin 75 mg slow release or a visually identical placebo with similar flavour was taken orally twice daily for 2.5 days. It was suggested that indomethacin affects the motor coordination required to avoid obstacles successfully during walking and that this effect will be even stronger when simultaneously performing a cognitive task that puts mental alertness to the test. Nineteen healthy middle-aged individuals (60 ± 4.7 years, eight female) performed an obstacle avoidance task on a treadmill), combined with a cognitive secondary task. Biceps femoris (BF) muscle response times, obstacle avoidance failure rates and composite scores ((100 × accuracy)/verbal response time) were used to evaluate the data.

No differences between indomethacin and placebo were found on the outcome measures regarding motor coordination, avoidance failure rates (P = 0.81) and BF response times (P = 0.47), nor on the performance on the secondary cognitive task (P = 0.12).

Even though surrogate methods were used, the current study provides evidence to suggest that there might be no need to caution patients who experience CNS side effects after indomethacin use to avoid activities requiring quick and adequate reactions, such as walking under challenging circumstances and maybe also driving a car.