Trippy World Different Forms of Ketamine: S-isomer vs. R-isomer

Different Forms of Ketamine: S-isomer vs. R-isomer

Different Forms of Ketamine: S-isomer vs. R-isomer

Ketamine, a potent dissociative anesthetic, has been used in medical settings for several decades. Originally developed as an alternative to phencyclidine (PCP) in the 1960s, ketamine gained popularity due to its unique pharmacological properties. It is classified as a non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist, leading to its dissociative effects. However, in addition to its role in anesthesia, ketamine has shown promise in managing various medical conditions, including treatment-resistant depression and chronic pain. Understanding the different forms of ketamine, particularly the S-isomer and R-isomer, is essential for medical professionals and researchers seeking to harness its therapeutic potential effectively. You can Buy ketamine online overnight at Trippy World

Chemical Structure of Ketamine

Ketamine is chemically known as 2-(2-chlorophenyl)-2-(methylamino)-cyclohexanone. Its molecular formula is C13H16ClNO, and it belongs to the class of arylcyclohexylamines. The compound exists in two enantiomeric forms, S-ketamine and R-ketamine, which are mirror images of each other. Enantiomers are chiral molecules that have the same chemical formula but differ in their spatial arrangement of atoms.

S-isomer Ketamine (S-Ketamine)

S-ketamine, also known as esketamine, is one of the two enantiomers of ketamine. It is the more potent form of ketamine and is primarily responsible for the drug’s anesthetic effects. However, its pharmacological properties extend beyond anesthesia. Here are some key points about S-ketamine:

  • Stereochemistry: S-ketamine is the (S)-enantiomer, and its chemical structure is a mirror image of R-ketamine’s (R)-enantiomer.
  • Pharmacological Properties: S-ketamine exhibits rapid onset and short duration of action, making it suitable for procedural sedation and induction of anesthesia.
  • Medical Applications:
    1. Anesthetic Effects: S-ketamine is widely used in anesthesia for surgeries, particularly in combination with other sedatives or analgesics.
    2. Treatment-Resistant Depression: Clinical studies have shown that intranasal S-ketamine, in the form of esketamine, can effectively treat individuals with treatment-resistant depression when used in combination with other antidepressant medications.
    3. Pain Management: S-ketamine has demonstrated potential in managing acute and chronic pain, especially in patients with neuropathic pain.

R-isomer Ketamine (R-Ketamine)

R-ketamine, also known as arketamine, is the other enantiomer of ketamine. While it is less potent than S-ketamine, it still possesses unique pharmacological properties that have attracted interest in the medical community. Here are some important facts about R-ketamine:

  • Stereochemistry: R-ketamine is the (R)-enantiomer, and its molecular structure is the mirror image of S-ketamine’s (S)-enantiomer.
  • Pharmacological Properties: R-ketamine is less potent than S-ketamine in terms of anesthesia but has its distinct effects and interactions with receptors.
  • Medical Applications:
    1. Anesthetic Effects: While R-ketamine is less commonly used for anesthesia than S-ketamine, it has been investigated for its anesthetic properties, especially in certain patient populations.
    2. Depression and Pain Management: Research is ongoing to explore the potential of R-ketamine in treating depression and managing pain conditions.

Mechanisms of Action

Both S-ketamine and R-ketamine interact with the brain’s NMDA receptors, leading to their dissociative and anesthetic effects. However, there are some differences in their mechanisms of action:

  • S-Ketamine: Its high affinity for NMDA receptors results in stronger dissociative and anesthetic effects.
  • R-Ketamine: While it also interacts with NMDA receptors, its effects are relatively weaker compared to S-ketamine.

Pharmacokinetics and Metabolism

The pharmacokinetics of ketamine, including its absorption, distribution, and elimination, vary between the S-isomer and R-isomer:

  • S-Ketamine:
    • Absorption: S-ketamine is rapidly absorbed when administered via intravenous or intranasal routes.
    • Distribution: It has a relatively large volume of distribution, indicating widespread distribution throughout the body.
    • Elimination: S-ketamine is metabolized in the liver and excreted primarily in the urine as various metabolites.
  • R-Ketamine:
    • Absorption: R-ketamine is also rapidly absorbed following intravenous or intranasal administration.
    • Distribution: It has a similar volume of distribution as S-ketamine, indicating comparable tissue distribution.
    • Elimination: R-ketamine undergoes hepatic metabolism and is excreted mainly in the urine.

Safety and Side Effects

Both forms of ketamine share common side effects, but there may be some differences in their intensity and frequency:

  • Common Side Effects: These can include nausea, vomiting, dizziness, sedation, and transient dissociative experiences.
  • S-Ketamine vs. R-Ketamine: Some studies suggest that S-ketamine may induce a more profound dissociative experience, while R-ketamine might be associated with fewer psychotomimetic effects.

While ketamine has a relatively safe profile when used in controlled medical settings, it is essential to consider potential differences in side effects when using S-ketamine versus R-ketamine.

Clinical Studies and Research

Numerous clinical studies have been conducted to investigate the efficacy and safety of both S-ketamine and R-ketamine in various medical conditions:

  • Depression: Both forms have shown promise in treating depression, particularly treatment-resistant depression. Esketamine, an intranasal form of S-ketamine, received FDA approval for this indication.
  • Pain Management: Studies have explored the use of ketamine, including both enantiomers, in managing acute and chronic pain conditions.
  • Anesthesia: S-ketamine remains the primary choice for anesthesia due to its potent and rapid effects, but research on R-ketamine’s potential in anesthesia is ongoing.

Current Use and Availability

The use and availability of S-ketamine and R-ketamine differ between countries and regulatory authorities:

  • Countries of Approval: Esketamine (S-ketamine) received approval for use in treating depression in certain countries, while R-ketamine is still under investigation for various indications.
  • Accessibility: The availability of these ketamine forms may vary based on local regulations and medical practices.

Recreational Use and Concerns

Ketamine is sometimes misused in non-medical settings, leading to potential health risks and concerns:

  • Misuse and Abuse: Recreational use of ketamine can lead to altered states of consciousness, dissociation, and hallucinations.
  • Risk Factors: Repeated or high-dose use may contribute to psychological dependence, cognitive impairments, and other adverse effects.
  • S-Ketamine vs. R-Ketamine: The recreational effects of both forms are generally similar, but individual responses may vary.

It is crucial to address the misuse of ketamine and educate the public about its potential risks.


In conclusion, ketamine is a powerful dissociative anesthetic with diverse pharmacological effects. Understanding the differences between its two enantiomers, S-ketamine and R-ketamine, is essential for maximizing their potential in medical applications. S-ketamine’s strength lies in its potent anesthetic properties and efficacy in treating depression and pain. On the other hand, R-ketamine offers its unique pharmacological effects, and ongoing research is shedding light on its medical applications. By carefully considering the pharmacokinetics, mechanisms of action, safety profiles, and clinical data, medical professionals and researchers can harness the full potential of ketamine to improve patient outcomes and well-being.


  • David Johnson

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