What did thalidomide change about how drugs are tested?

Thalidomide showed that a drug can pass every test of its day and still harm thousands, and that the tests themselves were the weak point. It was sold in West Germany from 1957, without a prescription, for anxiety, sleeplessness, tension and morning sickness. In 1961 it was withdrawn in Europe, after more than 10,000 infants, possibly 20,000, had been severely harmed, about 40% of whom died around birth.

How could this happen? Its toxicity had been checked in animals, but it was never tested on pregnant women, and at the time drugs did not have to be tested for effects on the unborn. They were tested for toxicity on rodents only.

One American official kept it off the US market. Frances Oldham Kelsey, a reviewer at the FDA, received the application from Richardson-Merrell in 1960. The FDA could only hold an application for 60 days at a time, so she asked the company for more information every 60 days for over a year, because the supporting testimonials contained no scientific methodology. The company demanded approval six times and was refused each time. Still, tablets handed out for "testing" led to 17 American children born with malformations.

The shock changed the law. In 1962 the Kefauver-Harris Amendment required manufacturers to prove their drugs were safe and effective.