(T1230-01-05) Charcoal Drug Adsorption Efficiency in Various Solvents

Purpose: The widespread abuse of prescription opioids has led to the development of abuse-deterrent formulations (ADFs). Charcoal (AC) is a non-absorbable adsorbent commonly used as a detoxifying agent in emergency settings [1]. AC prevents xenobiotics from being absorbed into the body by entrapping them and is taken orally or via a nasal feeding tube. AC has a large surface area that can adsorb drugs in different solvents and prevent their extraction [2]. In this study, we evaluated the effects of the drug's ionic nature and the effect of the solvent type on the charcoal’s adsorption efficiency as an abuse-deterrent agent.

Methods: Cationic Dextromethorphan HBr (DXM), anionic Diclofenac Sodium (DIC), and non-ionic Acetaminophen (APAP) were mixed with charcoal (1:8 ratio) in 10 mL of different solvents. The samples were vortexed for 30 seconds and then centrifuged at 1500 rpm for 5 min. The supernatant was extracted through a 0.2-micron filter before being analyzed for drug content using UV-Vis spectroscopy at 276 nm (DXM), 277 nm (DIC), and 248 nm (APAP). The solution's drug concentration was determined in reference to calibration curves established in each solvent. The % of the adsorbed drug was calculated from the mass balance. After centrifugation, the sediment dried, and it was analyzed by Differential Scanning Calorimeter (DSC) (25-350°C at 10°C/min) to confirm drug adsorption.

Results: According to Figure 1, drug adsorption was > 90% in 0.1N HCl for all the drugs. The extraction studies demonstrated > 90% adsorption of DEX in saline and NaHCO₃, ~70–80% in water and vinegar, and ~40% in 40% ethanol. The amount of DIC adsorption was enhanced to > 90% in water and vinegar, ~70% in ethanol and saline, and decreased to 6% in NaHCO₃ solution. In addition, > 90% APAP adsorption was observed in water, ethanol, and NaHCO_3, ~80% in vinegar, and ~40% in saline.The DSC thermograms in Figures 2, of DEX and Figure 3 APAP clearly showed the absence of the drugs’ endothermic melting peaks, confirming the drugs’ adsorption on the charcoal particles. The results of DIC in figure 3 was more challenging to interpret as the drug has no characteristic melting peak.

Conclusion: Regardless of drug structure, activated charcoal can effectively bind with different drug structures (anionic, cationic, and non-ionic). As such, it can effectively be used where a given drug needs to be separated from solutions. Moreover, all data shows that drug entrapment in charcoal is an adsorption process rather than binding as different drug structures show relatively high entrapment efficiency in all solutions.

References: 1. Neuvonen, P.J. and K.T. Olkkola, Oral activated charcoal in the treatment of intoxications. Medical toxicology and adverse drug experience, 1988. 3(1): p. 33-58.
2. Mastropietro, D.J. and H. Omidian, Abuse-deterrent formulations: part 2: commercial products and proprietary technologies. Expert Opin Pharmacother, 2015. 16(3): p. 305-23.

Acknowledgements: Funding for this work was provided by NSU Grant 3346622.


Figure 1: Drug Adsorption efficiency charcoal in various media


Figure 2: DSC thermograms of DXM A: dextromethorphan HBr (DXM), B: Activated charcoal, C: DXM AC in Water, D: DXM AC in Saline E: DXM AC in 40% ethanol F: DXM AC in NaHCO3.


Figure 3: DSC thermograms of Diclofenac Sodium and Acetaminophen