Drug information relevant to early 1959?

Back again! I'm getting close to finishing my current story, and I need some help with how to come close to killing off my main character. Basically, my bad guys is going to try to kill her off by forcing her to take enough pills to kill her. I don't know anything about what type of pills there would've been in '59, whether they had capsules, or tablets, or both, and I also don't know exactly what she's going to be poisoned with.

If possible, I would like the pills to cause her muscles to grow weak, and her breathing to slow, and eventually completely stop. I don't know what kind of life support systems they had in '59, but if they could've kept her heart going, a drug which would cause her heartbeat to drop dangerously low would work.

If you know a drug which would cause symptoms like that if you overdosed on it, or know a place with retro information on drugs, I'll be in heaven. Thanks.

Yeah, barbs match what I want right down to the letter. I took a peek on Wikipedia, and found an article on barbs, and managed to find one, Phenobarbital to be exact, which has been around for quite a while. The overdose symptoms are exactly what I want, so I have the drug of choice. Thanks!