Abstract
The purpose of this research was to prepare floating microballoons consisting of (i) calcium silicate as porous carrier; (ii) propranolol hydrochloride (PRH), an oral anti-hypertensive agent; and (iii) Eudragit S as polymer, by solvent evaporation method and to evaluate their gastro-retentive and controlled release properties. The effect of various formulation and process variables on the particle morphology, micromeritic properties, in-vitro floating behavior, percentage drug entrapment, and in-vitro drug release was studied. The gamma scintigraphy of the optimized formulation was performed in albino rabbits to monitor the transit of floating microballoons in the gastrointestinal tract. The propranolol hydrochloride-loaded optimized formulation was orally administered to albino rabbits, and blood samples collected were used to determine pharmacokinetic parameters of propranolol hydrochloride from floating microballoons. The microballoons were found to be regular in shape and highly porous. Microballoons formulation CS4, containing 200 mg calcium silicate showed the best floating ability (89 ± 4% buoyancy) in simulated gastric fluid as compared with other formulations. Release pattern of propranolol hydrochloride in simulated gastric fluid from all floating microballoons followed Higuchi matrix model and Peppas-Korsmeyer model. Prolonged gastric residence time of over 6 h was achieved in all rabbits for calcium silicate based floating microballoons of propranolol hydrochloride. The enhanced elimination half life observed after pharmacokinetic investigations in the present study is due to the floating nature of the designed formulations. Key words: Propranolol hydrochloride, calcium silicate, gastroretentive floating drug delivery, microballoons, gamma scintigraphy.
Highlights
Floating drug delivery is of particular interest for drugs that (i) act locally in the stomach, (ii) are primarily absorbed in the stomach, (iii) are poorly soluble at an alkaline pH, (iv) have a narrow window of absorption, and (v) are unstable in the intestinal or colonic environment (Singh and Kim, 2000).To provide good floating behavior in the stomach, the density of the device should be less than that of the gastric contents (≈1.004 g/cm3)
The tapped density values ranged from 0.43 ± 0.04 to 0.68 ± 0.06 g/cm3, while their true density ranged between 1.66 ± 0.12 and 1.94 ± 0.10 g/cm3
calcium silicate (CS)-based Eudragit microballoons were spherical in shape
Summary
Floating drug delivery is of particular interest for drugs that (i) act locally in the stomach, (ii) are primarily absorbed in the stomach, (iii) are poorly soluble at an alkaline pH, (iv) have a narrow window of absorption, and (v) are unstable in the intestinal or colonic environment (Singh and Kim, 2000). To provide good floating behavior in the stomach, the density of the device should be less than that of the gastric contents (≈1.004 g/cm). Srivastava et al (2005) reported cimetidine loaded floating microspheres of hydroxypropyl methylcellulose and ethyl cellulose. Sato et al developed hollow microspheres or microballoons (MB) of riboflavin, aspirin, salicylic acid, ethoxybenzamide, and indomethacin using Eudragit S100 as enteric polymer (Sato et al, 2003). Sato et al (2003) reported gamma scintigraphy of riboflavin- containing MB to establish its gastro-retention in human volunteers
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