PREVENTING DRUG EXTRACTION VIA SURFACE ADSORPTION

Objective. To investigate the correlation between drug properties and percentage of drug adsorbed onto the surface of activated carbon (medicinal charcoal). Background. Developing medications that prevent the easy extraction of drugs from dosage form is one strategy being used to decrease prescription drug abuse. Proposed methods being studied include viscosity modification, prodrug formation, drug antagonism, and ionic drug complexation. In this study, we introduce a new mechanism of abuse deterrence via surface adsorption onto activated carbon particles. Methods. Aqueous drug solutions containing low (200 μg/mL) and high (1000 μg/mL) concentrations of acetaminophen, diclofenac sodium, dextromethorphan hydrobromide, lidocaine hydrochloride, and verapamil hydrochloride were prepared. To 10 mL of each drug solution, increasing amounts of activated carbon (25, 50,100 mg) were then added. After 1 min, the solutions were centrifuged, the supernatant filtered, and drug concentration measured using UV-Vis spectroscopy at their corresponding wavelengths of 248, 275, 276, 263, and 278, respectively. The amount of drug bound to activated carbon was determined indirectly from the amount of free drug remaining in the supernatant. Results. Irrespective of the type of the drug used for surface adsorption, activated carbon showed above 80% entrapment when high drug concentrations were present. When graphed, adsorption was found to be linear with respect to the amount of activated carbon. However, activated charcoal showed as low as 36.6% entrapment for lidocaine hydrochloride and maximum of 100% entrapment for dextromethorphan hydrobromide in low concentration solutions. Conclusion. Activated carbon displayed rapid and highly effective surface absorption, providing effective drug entrapment over a broader range of weak acid, weak base and nonionic drugs. Grants. #PFRDG 335357, #PFRDG 33586