Experts say that most people are unfamiliar with drugs and which medications and doses would really kill them. The Madoffs could have been ignorant.
"We see people who take acetominophin (Tylenol) and end up in the hospital for two or three days getting life-saving treatment, and [they] didn't think it could have been that dangerous," said Casavant.
"Some people wake up surprised they are awake and think this should have killed them," he said. "And sometimes they are disappointed and mad at me for keeping life going."
Paul Doering, co-director of the Drug Information and Pharmacy Resource Center at the University of Florida, agreed that the average person "has no idea" how dangerous or toxic a drug might be.
"I have carried a beeper around with me for overdose patients and you get all types," he said. "Someone decides to end it all with 100 [tablets] of amoxicillin [an antibiotic] which won't kill you but probably [will] make you throw up. Others try to overdose on birth control pills."
Before the advent of newer, safer sleeping medications in 1970, the drugs most often associated with death were barbiturates like Seconal or Nembutal, which had a "narrow measure of safety," according to Doering.
Actresses Marilyn Monroe and Judy Garland overdosed on those drugs. Today, they are used in states that allow physician-assisted suicide and for lethal injections used in the death penalty.
Opioids, such as Ocycontin, can also be dangerous, especially in combination with benzodiazepines and alcohol.
Drug cocktails like these can paralyze "the most primate part of your brain," the respiratory center, said Doering.
Amy Winehouse's death earlier this year was ruled an alcohol overdose -- five times the legal limit -- that caused her breathing to stop.
Benzodiazepines have had a much greater safety record. Valium, the first member of the benzodiazepine family, was approved by the FDA in 1963 as a sedative-hypnotic that targets anxiety.
"The idea of any drug is to do all good things and spare the bad things," Doering said. "Sometimes, we can't separate that out. Drugs that relieve allergies give you dry mouth. One of the beautiful things about benzodiazepines is you can take a whole bunch of it and not reach the respiratory center in the brain."
Doering said he had a female patient who took 100 tablets of Valium, each 5 mg. She was "out like a light" for several days, but did not die.
"Benzodiazepines work effectively and wear off in a reasonable period of time with a low risk of overdose," he said. "They are safer in overdose that most medications. You would probably choke on the pill rather than die from the drug itself."
He guessed that with the combination of Ambien and Klonopin, the Madoffs "probably slept well for eight hours."
"If the Madoffs woke up the next day and felt reasonably well, they didn't take a whole lot of it," said Doering. "It's almost impossible to kill yourself on benzodiazepines."
"People shouldn't try to overdose on any meds," he said. "You could be the first one in medical history to die of a single intoxication of Klonopin or Ambien. But when you combine it with other drugs, all bets are off."
As for the Madoffs, "I am not surprised he woke up the next day," said Doering. "He couldn't even get the overdose right."