Background: Prussian Blue (PB) is available as conventional release dosage form “Radiogardase” with effective
daily dose 3-10 g (very high). The target site is duodenum where it inhibits enterohepatic circulation of Cs & Tl ions,
enhancing their fecal excretion.
Objective: To enhance efficacy, target release, reduce dose and side effects, oral pH dependent matrix formulation of PB
based on in-situ gelation of sodium alginate along with calcium salts was formulated and evaluated.
Methods: Different combinations of matrix granules were formulated and optimized. The optimized one was compressed
using Polyvinylpyrrolidone K30 (Pvp K30) in different batches and optimized. Langmuir adsorption isotherm was used to
assess in-vitro binding efficacy of formulation to thallium using atomic absorption spectroscopy. The proof of concept i.e.
drug release in duodenum was studied through pharmacoscintigraphy using radiolabeled formulation in rabbits.
Results: The optimized granules showed no drug release in acidic medium for 2 h whereas complete empty of basket in
basic medium within 30-60 minutes. The matrix tablet formulation with Pvp K30 (10% w/w) was optimized with desired
hardness and optimum in-vitro release profile. The release data fitted to various linear kinetic models, Hixson-Crowell r2
(0.9906) best fit, confirmed the erosion based release mechanism. The maximum binding capacity (MBC) was found
significantly higher (89.60 mg Tl/g formulation) than that of PB API (65.90 mg Tl /g PB API). Pharmacoscintigraphic
images confirmed intact formulation in stomach up to 2h and burst release in intestine thereafter.
Conclusion: The results exemplify oral pH dependent PB matrix formulation which achieved desirable target release at
duodenum and in-vitro binding efficacy towards Tl ion was appreciable.