Adsorption of antidepressant and cardiovascular drugs to activated charcoal: amitriptyline, bupropion, minoxidil, propranolol, and venlafaxine.

Background: Overdoses involving antidepressant and cardiovascular drugs account for 21.9% of non-opioid overdose-related fatalities in the United States. Activated charcoal is commonly used for gastrointestinal decontamination, but data regarding its adsorption efficacy for several clinically relevant drugs remain limited.

Objective: We aimed to evaluate the adsorption of amitriptyline, bupropion, minoxidil, propranolol, and venlafaxine to activated charcoal by fitting adsorption isotherm data.

Methods: Kinetics and adsorption isotherm experiments were conducted using simulated gastric fluid (pH 1.2) and simulated intestinal fluid (pH 6.8). Freundlich and Langmuir isotherm equations were fitted to experimental data to model adsorption behavior. Drug-specific activated charcoal-to-drug ratios required to achieve ≥95% adsorption were identified.

Results: All five drugs were adsorbed effectively to activated charcoal although adsorption efficiencies varied by pH. Maximal adsorption capacities of all drugs were higher in simulated intestinal fluid compared to simulated gastric fluid. In simulated intestinal fluid, ≥95% of bupropion was adsorbed at a 10:1 activated charcoal-to-drug ratio, while this level was not reached in simulated gastric fluid even at a 12:1 ratio. Amitriptyline and propranolol reached ≥95% adsorption at ratios below 10:1. Venlafaxine and minoxidil required higher ratios of activated charcoal ratios to reach maximal adsorption. Activated charcoal had a higher drug-binding capacity in simulated intestinal fluid, but binding was stronger in simulated gastric fluid. Bupropion was adsorbed more in simulated intestinal fluid overall, though efficiency decreased at higher concentrations.

Discussion: A single 50 g dose of activated charcoal at 10:1 ratio may be inadequate for clinically significant overdoses of bupropion, minoxidil, and venlafaxine, especially for immediate release bupropion for which gastric adsorption may be important.

Conclusions: This study supports the use of activated charcoal for gastrointestinal decontamination in overdoses involving amitriptyline, bupropion, minoxidil, propranolol, and venlafaxine. However, drug-specific differences in adsorption behavior suggest a need for refined dosing strategies, particularly in cases involving drugs with lower binding efficiencies.