Side effects of ofloxacin in clinical trials and in postmarketing surveillance.

Data derived from clinical trials of ofloxacin in 15,962 patients show that the incidence rate of adverse drug events was 4.27 per 100 patients. Symptoms were generally mild and related to the gastrointestinal tract, nervous system or hypersensitivity reactions in rank order. On the other hand, spontaneous reports obtained during postmarketing surveillance involving 1.5 million patients showed that the most frequent adverse drug events were related to the nervous system; next in order of frequency were hypersensitivity reactions and gastrointestinal symptoms. A comparison of the data obtained from clinical trials and postmarketing surveillance revealed no change in the favourable overall benefit:risk ratio of ofloxacin. Possible reasons for the different patterns of adverse drug events are discussed.