The Drugs That Killed Marilyn Monroe



The two major categories of sedative-hypnotics (anxiety/sleeping pills) are barbiturates and benzodiazepines. The chemical structure of the drugs in these groups are similar. In the 1950’s and early 60’s, barbiturates were routinely prescribed as a sleep-inducer. The most well known were Seconal (secobarbital) and Nembutal (pentobarbital). They were very common and if you lived at the time you would have frequently seen ads for these drugs in newspapers and magazines. Nembutal was even marketed as a sleep aid for children. They were routinely handed out to anyone who went to a doctor with the complaint of not being able to sleep. They were also used to treat anxiety.

At that time, benzodiazepines were relatively new and thus less common. In the years following Marilyn’s death, this situation would reverse. Benzodiazepines would eventually replace barbiturates as the most commonly prescribed sedatives. The most well known examples of benzodiazepines are Valium and Librium.

Today, the pentobarbital that killed Monroe has few medical uses in humans. It’s used by veterinarians to euthanize animals. In Europe (and where it’s legal in the US,) it’s also used in physician-assisted suicide.

Barbiturates depress the brain’s electrical activity. They work within brain tissue to reduce the firing of neurons. Barbs slow down brain function and put the brain to sleep. With too many, breathing is suppressed and the heart stops pumping as hard, leading eventually to death.


The chloral hydrate that Marilyn consumed usually receives very little attention when discussing the circumstances of Marilyn’s death. Nembutal has always been the star in this show and always gets top billing. If anyone had paid attention to the chloral hydrate, we might not have had over five decades of controversy surrounding Marilyn’s death. Any real investigation into Marilyn’s death should have uncovered where Monroe got this drug that contributed to her untimely demise. The chloral hydrate is important because no one can definitively say where it came from. And the fact that there was never an investigation into where the drug came from goes a long way towards proving there was a cover-up so the true circumstances of Monroe’s death would never be revealed.

So let’s take a look at why this drug is so important for answering questions about how and why Marilyn died. Chloral hydrate has been around for a long time. When first synthesized it was classified as a hypnotic. Hypnos is Greek for sleep, so hypnotic is a fancy way to say sleeping aid. Since it can be used to control anxiety it’s also considered a sedative. It was one of the first sedatives and was available long before barbiturates. By the mid 1800’s it could be found in all the best asylums. It was the go-to sleep aid because it could knock a person out fast. It’s dissolves easily in liquids, which is why it became they drug of choice in “Mickey Finn” concoctions. Legend has it that Mickey Finn was a saloon keeper in early 1900’s Chicago, who would use knock-out drops (chloral hydrate) to drug and rob his customers.

If you are trying to die, or want to kill someone, mixing chloral hydrate with another sedative is a good way to do it. When mixed, the two are said to increase the effects of each other. Anna Nicole Smith died of an accidental overdose after mixing chloral hydrate with a sedative. The Jonestown mass suicides involved drinking Flavor Aid (a soft drink beverage) poisoned with a mixture of drugs that included chloral hydrate and a sedative. The two are often used together today in physician assisted suicides. Chloral hydrate is a sedative-hypnotic drug that does not fit either major category of sedatives. It isn’t a barbiturate or a benzodiazepine. So to say Marilyn died of acute barbiturate poisoning isn’t technically correct. She died of a combination of sedative-hypnotic drugs.

Most of the conversation regarding Marilyn’s death focuses mainly on the Nembutal. The amount of Nembutal in Monroe’s system is always called a lethal dose. Sometimes the amount of chloral hydrate found in Monroe’s system is also called a lethal dose, sometimes it’s not. Even the coroner in charge of Marilyn’s case uses conflicting statements concerning whether it was a lethal or toxic dose. Chloral hydrate became a confusing element of the Monroe case right from the beginning. The first toxicology report from the coroner’s office on August 6, 1962, doesn’t even mention chloral hydrate. Initially the only tests requested from the autopsy surgeon listed on the first toxicology report were for ethanol (alcohol) and barbiturates. On the first toxicology report only the blood was tested. Alcohol was absent and the barbiturate level was 4.5 mg. per cent. Since a level of 1.5 mg% can kill a person, it was said there was enough drugs in her system to kill 3 people. That can be misleading because Monroe’s tolerance level was probably much higher than an average person. The amount found in her system was high, but no where near as high as what would be indicated by the hyperbole that would develop. Stories such as “there were enough drugs in her system to put down a heard of buffalo” or “enough to kill 15 people” are simply ridiculous and misleading.

One week after the first toxicology report, a second supplemental report was issued on August 13, 1962. This one reported that the blood contained 8 mg% of chloral hydrate. It also stated that a 13 mg% level of pentobarbital was found in the liver. What these numbers mean has been a source of constant debate ever since. Most “official” estimates of the number of pills Monroe took on the night of her death have been in the 40-50 range. Modern science says those initial estimates were too high. In this work I’m going to use the recent estimates of renowned forensic pathologist, Dr Cyril Wecht, who says the numbers indicate Monroe took 5 chloral hydrates and 12-24 Nembutal capsules.

All early sources reference Dr Engelberg as having prescribed Marilyn the Nembutal. Engelberg himself revealed this to the authorities. Confusion soon developed over how many and when these were prescribed. Was it 50 or 25? (It turned out to be two prescriptions for 25.) Was the second a refill or a new prescription? When was the first prescription filled? Those question’s are a little harder to answer, you’ll find sources with conflicting information. The only thing clear is that Dr Engelberg gave Marilyn what he calls a refill on August 3, 1962 for 25 capsules of Nembutal, but the vial itself appears to be an original prescription and not a refill. This anomaly has always led to the question of whether Monroe had enough Nembutal on hand to account for the levels found in her system. Following Marilyn’s death, Dr Greenson is quoted as saying he did not know about this Nembutal prescription. Greenson says he turned over all prescription related duties to Engelberg, and the internist was supposed to notify him if he prescribed Marilyn Nembutal. Greenson and Engelberg were said to be coordinating in an effort to decrease her reliance on pills. Greenson reportedly had instructed Engelberg to switch her to a milder sedative. Librium was found on Marilyn’s nightstand and I believe this is the milder sedative Engelberg had been prescribing during the months before Monroe’s death. With all this attention on the Nembutal, it never seemed to occur to anyone to ask, “Who prescribed the chloral hydrate?” Since Dr Greenson had prescribed Marilyn chloral hydrate during the filming of The Misfits, it’s often assumed he was the one to prescribe it. It wouldn’t even become an issue until the LA District Attorney reopened the case in 1982. By this time Greenson had died, and only Engelberg was left to answer when the question was finally raised. Back in 1962, multiple prescriptions of different kinds were found on Monroe’s nightstand. It seems at that time, anything that hadn’t come from Engelberg was assumed to have come from Dr Lee Siegel, the Fox studio doctor. But in 1982 Siegel denied prescribing the chloral hydrate, and Engelberg said he hadn’t prescribed it either. Engelberg didn’t believe Greenson had given it to her and he assumed no doctor in the US would have still prescribed it. He assumed she had got it in Mexico, and that’s the story he would maintain in all future interviews. This issue was never resolved and it goes a long way towards proving there never was a serious investigation of this case. Not in 1962, nor again in 1982.

Fast forward to the modern internet age. Within the last 20 years there has been an intense interest in Marilyn memorabilia. Anything even remotely associated with the icon continues to find it’s way onto online auctions. Every scrap of paper that was ever in the vicinity of Monroe has been photographed, cataloged and sold online. Included in this vast assortment of ephemera are actual copies of prescriptions from Marilyn’s last summer. One of those prescriptions just so happens to be one for chloral hydrate, and it’s from Dr Engelberg! “Liar, liar, pants on fire,” came the cry from the Marilyn community. It was said that, “Engelberg had been lying and here’s the proof.” Unfortunately for Engelberg, he was no longer alive to answer his critics. New documentaries were produced charging Engelberg with medical negligence. Engelberg took his place in the Marilyn “blame game,” among such notable villains as, JFK, RFK, Greenson, Murray, Hoover, Hoffa, Castro, the FBI, the CIA, Giancana and a couple of thugs named Needles and Mugsy; and even our reptilian overloads. Was the blame warranted? Things are rarely cut and dry in the Monroe case. Researching Marilyn is like being sucked into a black hole that leads to a vortex of contradictions, wrapped around a riddle, who’s center is an enigma. There is never easy answers, and this piece of evidence ultimately leads to more questions. What do I mean? If you do an image search online for Engelberg, Monroe, prescription and Librium, you will be led to a photo of another prescription from that summer. This one is an Engelberg prescription for Librium. This is the drug I believe Greenson had switched Marilyn to when he came back from his vacation in June, when he began to coordinate with Engelberg to reduce Monroe’s dependence on pills. This is an “official” Engelberg prescription, complete with his name and the address of his practice at the top. Now do an image search with these search terms: chloral hydrate, Engelberg, Monroe and prescription. You should find a chloral hydrate prescription from Engelberg dated June 1962. Compare this prescription with the one for Librium. The unmistakable conclusion from this comparison is that the handwriting doesn’t match! The Engelberg signatures on each document aren’t the least bit similar. How can this anomaly be explained. Three possible explanations are: the prescriptions are fakes, someone forged Engelberg’s signature or the prescriptions were phoned into the pharmacy. But even this last possibility doesn’t prove they were phoned in by Engelberg, it could have been someone masquerading as Engelberg. The Nembutal in Marilyn’s system was enough to kill her and it’s clear it was prescribed by Engelberg. Why would he lie about the chloral hydrate? This new evidence throws a curve ball into the investigation of Marilyn’s death. It requires new theories to accommodate this information. What follows are two new scenarios concerning Marilyn’s last summer that try to explain where the mystery prescriptions came from and the part they played in her death.

The Drugs that Killed Marilyn Monroe - Chloral Hydrate