John Oliver returned from a three-month hiatus on Sunday, setting his sights on big pharmaceutical companies and their marketing schemes.

"Drug companies are a bit like high-school boyfriends," Oliver said. "They're much more concerned with getting inside you than being effective once they're in there."

Oliver pointed out pharmaceutical companies spent more than $24 billion marketing to doctors in 2012. He also cited one report that found nine out of 10 big drugmakers spent more marketing than researching drugs, with some spending roughly twice as much on marketing as research.

"Drug companies know that doctors hold all the real power in the prescription drug business," Oliver said.

Oliver told viewers — and Twitter followers — to check out the federal government's open payments website to see how much money their doctors get from pharmaceutical companies. The website seemingly couldn't handle the swarm of fans, appearing to crash throughout the night.

If you’d like to see how much payment your doctors have received from pharmaceutical manufacturers, check here: https://t.co/1yCBiSiU2x — Last Week Tonight (@LastWeekTonight) February 9, 2015

Further reading: Create your own hyperviolent John Oliver headlines.