Despite being perfectly sane, a character is given drugs that make people around him think that he is insane. This is usually done maliciously and without the character's knowledge. Frequently done to get a character out of the way when killing them would be too messy, or simply to discredit them
Often this would be maintained by having a caregiver giving the patient "medicine" to treat their mental illness, but in reality is dosing them to keep them insane. May be administered by Slipping a Mickey and/or Water Source Tampering.
Compare Psycho Serum where a character intentionally takes a drug to enhance himself, but it induces insanity as a side-effect; also compare Infectious Insanity where insanity is induced by contact with an already insane person, and Mushroom Samba for cases where a character is under the influence of hallucinogens (voluntarily or otherwise). See also Gaslighting, another way in which one character can make another seem insane.
See also Munchausen Syndrome and the "by proxy" variant.
- In the Tintin album "Cigars of the Pharoah", the Egyptologist Dr. Sarcophagus is given drugs to make him insane, so as to cover up an opium-smuggling ring that was running through Egypt. The Rajaijah Juice or "poison of madness" then pops up again in next album "The Blue Lotus", though at the end of the album, Dr. Fang (who was kidnapped by the drug ring because they feared his research on madness) develops a cure for its effects.
- In Dragonheart: A New Beginning, the king's apparent senility proves to be caused by drugs administered by the Big Bad.
- Nightbreed: Doctor Decker convinces his patient Aaron Boone that he is responsible for a horrible series of murders that have plagued the city for the past several months, then he prescribes him some anti-psychotic drugs. It turns out that the drugs were actually intended to make Boone psychotic: Decker is the real killer who is trying to cover up his own crimes by framing Boone.
- In Red, Marvin is clearly shown to be a bit insane. Then Frank reveals to Sara (and the audience) he'd been secretly fed LSD for 11 years.
- In Dragon Blood, the protagonist is given drugs as part of a plot to make him seem unfit to rule. The reader gets to know what he thinks his surroundings look like (people talking to him are monsters, etc).
- In Crash Deluxe, Parrish Plessis is nearly driven insane by Glorious and her powerful pheromone blends.
- In the opening of the Venus Prime series, Sparta has spent several years of her life being drugged into oblivion by the Free Spirit.
- In the Warhammer 40,000 novel Blood Angels: Deus Encarmine the traitorous Inquisitor Stele drugs a Blood Angel who stumbled onto his plot to trigger the Black Rage in him.
- In John D. MacDonald's Travis McGee novel Nightmare in Pink, McGee has a hallucinatory drug slipped into his drink. When he loses control, he's taken into custody by the bad guys and sent to a mental hospital so he can be interrogated and lobotomized.
- In Jonathan Strange & Mr Norrell, Mr. Strange Invokes this on himself: realizing that The Fair Folk are visible to madmen even when they're making themselves Invisible to Normals, he creates an alchemical distillation of insanity and spends a few days wandering around Venice in a hallucinatory stupor. It even lets him find the Gentleman with Thistledown Hair, to the Gentleman's considerable surprise, though he's too loopy to realize it until after the fact.
- The Kingkiller Chronicle: Ambrose doses Kvothe with an alchemical concoction that leaves him The Sociopath for a few hours, intending him to embarrass himself at an important moment. Although Kvothe runs his mouth in front of a younger student and has to be restrained from nonchalantly murdering Ambrose when Kvothe learns what's been done, his friends manage to get him to privacy before he does any real damage.
- In The Celebrated Cases of Judge Dee a woman who murdered her husband to have an affair with a neighbor gave her daughter a drug that rendered her unable to speak comprehensibly to keep her from exposing her. During the trial Judge Dee cures the daughter so she can testify.
- In The Stainless Steel Rat, Jim has trouble predicting a psychopathic murderer's next move, so he takes a drug combination temporarily giving him the same kind of insanity.
- Vatta's Peace: In Into the Fire, the people who survived Miksland with Ky Vatta in the previous book have been quarantined and drugged into a stupor by The Conspiracy for fear that what they saw on the supposedly uninhabitable continent could derail their Evil Plan.
- Kushiel's Legacy: In Kushiel's Mercy, Imriel has a spell cast on him, in the form of being stuck with a steel needle soaked in the sweat of a madman, to drive him insane for several weeks so that he isn't affected by a Fake Memories spell that another party cast on the entire city.
- Hercule Poirot: The Cretan Bull (part of The Labours of Hercules): the "bull" in this case is a huge and energetic young man named Hugh who is suffering from hallucinations and sometimes wakes up with bloodied hands and the news that animals have been found butchered nearby. As his family has a history of congenital madness, he's afraid of going off the deep end and resolves to commit suicide when he thinks he's close to harming his fiancé. He's perfectly sound in mind, the hallucinations being produced by drugs in his shaving cream. The actual madman is his father- or rather, his mother's husband, who does suffer from the family insanity and resolved to drive Hugh to suicide in revenge, having murdered his wife years ago. He shoots himself once found out.
- One of the viewpoint characters of Rule 34 by Charles Stross is a contract killer who ended up with a form of paranoid schizophrenia due to medical experiments on him, and now has to take drugs to remain lucid. He's fortunate in one case that Scotland still has a National Health System (England has apparently gotten rid of theirs) which supplies it for free.
- In A Caribbean Mystery, this turned out to be the chief cause of Molly Kendal's mental instability. The guilty party kept drugging her for a long while so that her eventual murder would look like suicide.
- Inverted in a Lord Peter Wimsey short story, where the villain withholds a drug that the victim needs to stay mentally healthy.
- In Heavy Weather by Bruce Sterling, a member of the conspiracy doesn't like the protagonist staring at him, so threatens to inject her with a drug that will do this.
- Joe Pickett: The bad guys in Out of Range use psychoactive drugs added to his drinking water and psychological trickery to turn game warden Will Jensen's depression into paranoia, which ultimately drives him to suicide.
- Sierra's backstory in Dollhouse. After spurning the advances of a rich man, he is so angered that he doses her and has her put into a mental ward. She is then turned into an Active, a programmable love slave hired out to rich clients, which includes the man responsible for her state.
- Used a few times in Psych:
- In "Shawn Flew Over the Cuckoo's Nest," Shawn goes into a mental ward to try to prove that a crimelord is faking insanity to get an Insanity Defense. Turns out this trope is at play instead, and he is being continually dosed by one of the nurses.
- Happens to Lassiter in "Heeeeeere's Lassie", where the killer is putting a chemical in the air vents to drive certain residents insane.
- Occurs yet again when a law firm has a man dosed so that people think he's an insane conspiracy nut to discredit them when he is building a case against them when he finds that they've had some shady dealings.
- In It's Always Sunny in Philadelphia, Frank ODs on a number of mental medications, leading to him wandering the street in soiled pants. He then gets taken to a mental ward (an Actor Allusion, as Danny DeVito was in One Flew Over the Cuckoo's Nest). Once the medication wears off, he breaks out.
- Law & Order: Special Victims Unit:
- One episode has a villain of the week who has a girl she was abusing (who witnessed her murder another child in her care) committed and drugged (she managed to convince the staff that the girl was legitimately insane, but the trope was otherwise in effect).
- Another episode inverts it, by having a corrupt nursing home take a patient off his meds to prevent him from telling anyone about a patient who died due to negligence.
- The X-Files: In the second season finale, it is revealed that Mulder's erratic behavior of late was due to drugs in his water supply, presumably done by The Conspiracy to discredit him.
- Diagnosis: Murder, season 6, episode 6 'Alienated': in a possible Shout-Out to The X-Files and its 'Anasazi' episode a doctor is poisoned by a pharmaceutical company inducing paranoia regarding a secret military base to destroy his credibility in respect to a new drug.
- Inverted in an episode of Leverage where Parker checks into an addiction-treatment center as part of the team's latest con, where she is given anti-depressants and becomes temporarily relieved of her kleptomaniacal tendencies.
- In an episode of Get Smart Max gets a Tap on the Head and is diagnosed with amnesia. He's given some pills which are supposed to help. However, the doctor is actually working for KAOS and the pills cause amnesia. Every hour, just as he's starting to remember things, he has to take a pill which sets him back to square one.
- The Endeavour episode "Canticle" has the murderer giving massive doses of LSD to their victims in order to make killing them easier, or even having them get themselves killed in a delirious state. One of the intended victims does survive, but is left in an insane state from which we are told they may never recover.
- An episode of The Pretender had Jarod investigating a woman with a psychological condition. She's on medication, but it doesn't seem to help. At one point, she accidentally drops one of the pills into a glass of water. When the water turns red as a result, he realizes the medication is not what she thought and leads him to discover it's what's causing her condition.
- The Cosby Mysteries. A Victim of the Week is poisoned with mercury placed on his desklamp; the heat of the lightbulb vapourised the mercury and he inhaled the fumes, making him as mad as the proverbial hatter.
- In the Stingray (1985) episode "Playback", this turns out to be the cause of the violent deaths of most participants in an isolation experiment: A fire burnt some piping in the backup ventilation system, causing madness-inducing fumes to be ventilated throughout the building during a test of said backup system. The Sole Survivor was unaffected because he was doing a space walk simulation at the time, and thus on an independent air supply.
- Dungeons & Dragons supplement Unearthed Arcana. The Elixir of Madness is a magical liquid that causes anyone who drinks it to go insane. If it is slipped into someone's drink, it will cause them to go mad when they drink it. The victim can be restored to normal by one of three high level spells: Heal, Restoration or Wish.
- In We Happy Few, the entire populace of Wellington Wells is addicted to "Joy", which causes people to forget their troubles (especially the "Very Bad Thing") but also causes hallucinations and erratic behavior. Those who are not on Joy are brutally attacked by users until they either give in and take the drug, or are killed.
- In Assassin's Creed: Brotherhood, Ezio is able to give drugs to make the target assault passer-bys, much like a spree killer.
- In Hitman: Blood Money, Agent Smith is given drugs to make him look as The Alcoholic.
- SCP Foundation: Dr. Clef once held an orientation meeting with new researchers on the subject of Reality Warpers. He'd spiked the food and drink with hallucinogens so that when he started yelling at them that reality was being changed, they believed it, driving home just how helpless you are against such SCPs.
- The Simpsons: In one "Treehouse of Horror" story, Kodos and Kang spray Homer with rum so people will dismiss his alien-abduction story as drunken ravings.
- Star Wars: The Clone Wars: Fives finds out about the chips in the clones that will force them to kill the Jedi when Order 66 is activated. The Kaminoans drug him with something that makes him ultra paranoid. This combined with Palpatine telling him the truth about everything has Fives acting more and more deranged until he is killed by security clones. No one believes his ranting. Although the sequel series shows that at least a few believed him.