Author: Sergio Zuazo and Bruno Santiago
Cureus, July 5, 2026
Combining S-ketamine and dexmedetomidine in a single infusion may simplify drug administration and reduce the number of infusion pumps required during anesthesia or procedural sedation. However, the physical and chemical stability of this specific mixture had not previously been established.
This laboratory study evaluated whether an S-ketamine-dexmedetomidine mixture remained stable for 24 hours under ordinary laboratory conditions and whether ultraviolet light caused either drug to degrade.
Methods
The investigators prepared a mixture containing equal concentrations of S-ketamine and dexmedetomidine at 0.25 mM each.
The solutions were placed in clear borosilicate glass vials and studied under two conditions:
• Ambient laboratory light and room temperature for 24 hours
• Ultraviolet light exposure at 254 nm for up to 24 hours
Stability was assessed using high-performance liquid chromatography with diode-array detection. Mass spectrometry was used to characterize newly appearing degradation products.
A mixture was considered stable when at least 90% of the original drug concentration remained and there were no important changes in pH, precipitation, turbidity, or chromatographic appearance.
Key findings
Under ambient laboratory conditions, the S-ketamine-dexmedetomidine mixture remained physically and chemically stable for the entire 24-hour observation period.
There was:
• No significant loss of either drug
• No evidence of interaction between S-ketamine and dexmedetomidine
• No precipitation or turbidity
• No clinically meaningful change in pH
• No additional chromatographic peaks suggesting degradation
The pH remained stable between approximately 5.8 and 5.9.
Ultraviolet-light exposure
Exposure to ultraviolet light caused progressive degradation of S-ketamine.
A new degradation-product peak appeared after ultraviolet exposure and increased over time. Mass spectrometry identified a product with a mass-to-charge ratio of 220, compared with 238 for S-ketamine.
The investigators concluded that this product was probably formed by the loss of a water molecule from S-ketamine.
Dexmedetomidine remained stable during ultraviolet exposure, and there was no evidence that the two anesthetic drugs reacted with one another.
Clinical significance
The study supports the physical and chemical compatibility of combining S-ketamine and dexmedetomidine in the same solution for periods of up to 24 hours under standard indoor conditions.
The combination is pharmacologically attractive because:
• S-ketamine provides analgesia and sedation while generally preserving spontaneous breathing and sympathetic tone.
• Dexmedetomidine provides sedation and analgesia with minimal respiratory depression.
• Dexmedetomidine may reduce some ketamine-associated sympathetic and emergence effects.
• Ketamine may offset some dexmedetomidine-associated hypotension and bradycardia.
A stable single mixture could simplify administration, reduce equipment requirements, and potentially lower material use and operating costs.
Handling implications
The mixture should be protected from ultraviolet light during preparation, storage, and administration.
Although ordinary room lighting did not cause significant degradation during the study, appropriate precautions may include:
• Avoiding direct ultraviolet exposure
• Using light-protective containers or tubing when prolonged exposure is possible
• Storing the mixture away from ultraviolet disinfection devices or direct sunlight
• Preparing and labeling the admixture using standardized pharmacy or anesthesia protocols
Important limitations
This was an in vitro laboratory study and did not involve patients.
The investigators did not evaluate:
• Clinical efficacy
• Pharmacodynamic interactions
• Pharmacokinetics
• Hemodynamic effects
• Respiratory safety
• Sedation quality
• Toxicity of the ultraviolet degradation product
Only one drug concentration, one type of container, and a 24-hour storage period were studied. The results may not apply to different concentrations, diluents, syringes, infusion bags, tubing materials, temperatures, or longer storage periods.
The discovery of physical and chemical stability does not by itself prove that the mixture is safe or effective for clinical administration.
Bottom line
An admixture containing S-ketamine and dexmedetomidine remained physically and chemically stable for 24 hours under standard laboratory light and room-temperature conditions.
Ultraviolet exposure caused progressive degradation of S-ketamine, while dexmedetomidine remained stable.
The mixture should therefore be protected from ultraviolet light. These findings support further clinical studies but are not sufficient by themselves to establish patient safety, dosing recommendations, or clinical effectiveness.
Thank you to Cureus for allowing us to summarize this article.