If people voluntarily take drugs that make them invalids, fully knowing the risks, what lawsuit would account for that? People still voluntarily smoke now, knowing that there's a very good chance it'll kill them.
It's that people smoke knowing that it will kill them but that's something different. Think about the dangers of illegal drugs - the chemical itself isn't generally the problem, it's the impurities / bad manufacturing.
If you were buying drugs over the counter you wouldn't expect to hit on a batch that contained a poisonous substance. Drug companies would be very careful to make sure that doesn't happen.
