On the basis of calculated cumulative hazard rates for initial occurrence of adverse experiences of patients following treatment for rheumatoid arthritis and osteoarthritis, a simple function is evolved that fits such cumulative hazard rate data very well. From this simple function, we obtain the estimated hazard rate in terms of two physically meaningful parameters. These two parameters can be used to describe the rate of occurrence of adverse experiences, and to convey the concept of risk of adverse experience associated with duration of exposure to a drug.