Ketamine is the drug most pharmacologically similar to PCP (phencyclidine). Both belong to the same chemical family, block the same receptor in the brain, and produce the same core effect: dissociation, a trance-like state where a person feels detached from their body and surroundings. If you encountered this as a test question, ketamine is almost certainly the correct answer, but several other drugs share meaningful similarities with PCP as well.
Why Ketamine Is the Closest Match
PCP and ketamine are both arylcyclohexylamines, a chemical class defined by a shared molecular backbone. They work the same way in the brain: both are non-competitive antagonists of NMDA receptors, meaning they block a key receptor involved in learning, memory, and sensory processing. When that receptor is blocked, the result is numbness, altered perception, and at higher doses, a full dissociative state where someone feels completely separated from reality.
Both drugs were originally developed as surgical anesthetics. PCP came first but was pulled from human use in 1967 because patients woke up with severe agitation, hallucinations, and dysphoria. Ketamine was developed as a replacement with a similar mechanism but lower receptor affinity and a shorter duration of action, which translates to fewer of those disturbing side effects. Ketamine remains in clinical use today for anesthesia and, more recently, for treatment-resistant depression.
The two drugs also share a distinctive cardiovascular fingerprint. Unlike most anesthetics, which lower blood pressure and heart rate, both PCP and ketamine raise them. Ketamine during procedural sedation increases systolic blood pressure by about 8 mmHg and heart rate by about 13 beats per minute on average. This stimulant-like effect on the heart is unusual among drugs that also cause sedation and is one of the hallmarks of the arylcyclohexylamine class.
How PCP and Ketamine Differ
Despite their similarities, the two drugs are not interchangeable. PCP binds more tightly to NMDA receptors, which means its effects are stronger and last much longer. A typical PCP experience lasts up to 3 hours at standard doses but can stretch to 1 to 4 days after an overdose. Ketamine, by contrast, wears off in roughly 45 to 90 minutes in most clinical settings. PCP also interacts with a broader range of receptors in the brain, contributing to its more unpredictable and often aggressive psychological effects.
Their legal classifications reflect this gap in risk. PCP is a Schedule II controlled substance, meaning it has some recognized medical potential but high abuse liability. Ketamine sits at Schedule III, indicating a lower (though still real) potential for dependence.
Other Drugs in the Same Family
Several other compounds share PCP’s arylcyclohexylamine structure and NMDA-blocking mechanism. The most notable ones:
- Eticyclidine (PCE): One of the earliest PCP derivatives, synthesized in the 1960s alongside ketamine. Its effects were considered too powerful for medical use. In animal studies comparing how closely various drugs mimic PCP’s behavioral effects, PCE ranked as the most potent PCP substitute. It is a Schedule I substance.
- Tenocyclidine (TCP): Another close structural analog of PCP, also Schedule I. It produces similar dissociative effects but never found a medical application.
- Methoxetamine (MXE): A designer drug first identified in the United Kingdom in 2010. MXE binds to the same site on the NMDA receptor as PCP with comparable affinity. In lab studies, MXE produced PCP-like effects at lower doses than PCP itself, though PCP’s peak effect was still stronger overall. Effects take 30 to 90 minutes to kick in.
- 3-MeO-PCP: A methoxy derivative of PCP that produces similar hallucinogenic effects. The DEA placed it in Schedule I in 2025, citing its chemical and pharmacological similarity to PCP.
These analogs are primarily encountered as illicit or designer drugs. None are used in mainstream medicine.
DXM: An Over-the-Counter Dissociative
Dextromethorphan (DXM), the cough suppressant found in many cold medications, also produces PCP-like effects at high doses. At the doses found in a normal cough syrup serving, DXM simply suppresses coughs. But at recreational doses of 300 to over 1,500 mg, DXM and its active metabolite block NMDA receptors in the same way PCP and ketamine do.
Recreational users describe a dose-dependent progression of effects sometimes called “plateaus.” At moderate recreational doses (roughly 500 to 1,000 mg), users experience visual and auditory disturbances, altered consciousness, and partial dissociation. Above 1,000 mg, the effects escalate to full dissociation, hallucinations, and delusions. While DXM is structurally different from PCP (it is not an arylcyclohexylamine), its high-dose effects overlap enough that emergency physicians consider it in the same clinical category of dissociative intoxication.
Why This Matters on an Exam
If you’re answering a multiple-choice question, the answer is almost always ketamine. It matches PCP on every important axis: chemical class, mechanism of action, clinical effects, and medical history as an anesthetic. DXM is a reasonable second choice if the question specifically asks about over-the-counter drugs or NMDA antagonism more broadly. PCE, TCP, and MXE are closer to PCP in some ways but rarely appear as answer choices outside specialized pharmacology courses.
The key concept being tested is NMDA receptor antagonism. PCP was the original drug in this class, ketamine was its direct clinical successor, and every other PCP-like drug works through the same fundamental mechanism of blocking that receptor to produce dissociation, analgesia, and at high doses, hallucinations.